1.. SPDX-License-Identifier: GPL-2.0 2 3==================== 4The /proc Filesystem 5==================== 6 7===================== ======================================= ================ 8/proc/sys Terrehon Bowden <terrehon@pacbell.net>, October 7 1999 9 Bodo Bauer <bb@ricochet.net> 102.4.x update Jorge Nerin <comandante@zaralinux.com> November 14 2000 11move /proc/sys Shen Feng <shen@cn.fujitsu.com> April 1 2009 12fixes/update part 1.1 Stefani Seibold <stefani@seibold.net> June 9 2009 13===================== ======================================= ================ 14 15 16 17.. Table of Contents 18 19 0 Preface 20 0.1 Introduction/Credits 21 0.2 Legal Stuff 22 23 1 Collecting System Information 24 1.1 Process-Specific Subdirectories 25 1.2 Kernel data 26 1.3 IDE devices in /proc/ide 27 1.4 Networking info in /proc/net 28 1.5 SCSI info 29 1.6 Parallel port info in /proc/parport 30 1.7 TTY info in /proc/tty 31 1.8 Miscellaneous kernel statistics in /proc/stat 32 1.9 Ext4 file system parameters 33 34 2 Modifying System Parameters 35 36 3 Per-Process Parameters 37 3.1 /proc/<pid>/oom_adj & /proc/<pid>/oom_score_adj - Adjust the oom-killer 38 score 39 3.2 /proc/<pid>/oom_score - Display current oom-killer score 40 3.3 /proc/<pid>/io - Display the IO accounting fields 41 3.4 /proc/<pid>/coredump_filter - Core dump filtering settings 42 3.5 /proc/<pid>/mountinfo - Information about mounts 43 3.6 /proc/<pid>/comm & /proc/<pid>/task/<tid>/comm 44 3.7 /proc/<pid>/task/<tid>/children - Information about task children 45 3.8 /proc/<pid>/fdinfo/<fd> - Information about opened file 46 3.9 /proc/<pid>/map_files - Information about memory mapped files 47 3.10 /proc/<pid>/timerslack_ns - Task timerslack value 48 3.11 /proc/<pid>/patch_state - Livepatch patch operation state 49 3.12 /proc/<pid>/arch_status - Task architecture specific information 50 51 4 Configuring procfs 52 4.1 Mount options 53 54 5 Filesystem behavior 55 56Preface 57======= 58 590.1 Introduction/Credits 60------------------------ 61 62This documentation is part of a soon (or so we hope) to be released book on 63the SuSE Linux distribution. As there is no complete documentation for the 64/proc file system and we've used many freely available sources to write these 65chapters, it seems only fair to give the work back to the Linux community. 66This work is based on the 2.2.* kernel version and the upcoming 2.4.*. I'm 67afraid it's still far from complete, but we hope it will be useful. As far as 68we know, it is the first 'all-in-one' document about the /proc file system. It 69is focused on the Intel x86 hardware, so if you are looking for PPC, ARM, 70SPARC, AXP, etc., features, you probably won't find what you are looking for. 71It also only covers IPv4 networking, not IPv6 nor other protocols - sorry. But 72additions and patches are welcome and will be added to this document if you 73mail them to Bodo. 74 75We'd like to thank Alan Cox, Rik van Riel, and Alexey Kuznetsov and a lot of 76other people for help compiling this documentation. We'd also like to extend a 77special thank you to Andi Kleen for documentation, which we relied on heavily 78to create this document, as well as the additional information he provided. 79Thanks to everybody else who contributed source or docs to the Linux kernel 80and helped create a great piece of software... :) 81 82If you have any comments, corrections or additions, please don't hesitate to 83contact Bodo Bauer at bb@ricochet.net. We'll be happy to add them to this 84document. 85 86The latest version of this document is available online at 87http://tldp.org/LDP/Linux-Filesystem-Hierarchy/html/proc.html 88 89If the above direction does not works for you, you could try the kernel 90mailing list at linux-kernel@vger.kernel.org and/or try to reach me at 91comandante@zaralinux.com. 92 930.2 Legal Stuff 94--------------- 95 96We don't guarantee the correctness of this document, and if you come to us 97complaining about how you screwed up your system because of incorrect 98documentation, we won't feel responsible... 99 100Chapter 1: Collecting System Information 101======================================== 102 103In This Chapter 104--------------- 105* Investigating the properties of the pseudo file system /proc and its 106 ability to provide information on the running Linux system 107* Examining /proc's structure 108* Uncovering various information about the kernel and the processes running 109 on the system 110 111------------------------------------------------------------------------------ 112 113The proc file system acts as an interface to internal data structures in the 114kernel. It can be used to obtain information about the system and to change 115certain kernel parameters at runtime (sysctl). 116 117First, we'll take a look at the read-only parts of /proc. In Chapter 2, we 118show you how you can use /proc/sys to change settings. 119 1201.1 Process-Specific Subdirectories 121----------------------------------- 122 123The directory /proc contains (among other things) one subdirectory for each 124process running on the system, which is named after the process ID (PID). 125 126The link 'self' points to the process reading the file system. Each process 127subdirectory has the entries listed in Table 1-1. 128 129Note that an open file descriptor to /proc/<pid> or to any of its 130contained files or subdirectories does not prevent <pid> being reused 131for some other process in the event that <pid> exits. Operations on 132open /proc/<pid> file descriptors corresponding to dead processes 133never act on any new process that the kernel may, through chance, have 134also assigned the process ID <pid>. Instead, operations on these FDs 135usually fail with ESRCH. 136 137.. table:: Table 1-1: Process specific entries in /proc 138 139 ============= =============================================================== 140 File Content 141 ============= =============================================================== 142 clear_refs Clears page referenced bits shown in smaps output 143 cmdline Command line arguments 144 cpu Current and last cpu in which it was executed (2.4)(smp) 145 cwd Link to the current working directory 146 environ Values of environment variables 147 exe Link to the executable of this process 148 fd Directory, which contains all file descriptors 149 maps Memory maps to executables and library files (2.4) 150 mem Memory held by this process 151 root Link to the root directory of this process 152 stat Process status 153 statm Process memory status information 154 status Process status in human readable form 155 wchan Present with CONFIG_KALLSYMS=y: it shows the kernel function 156 symbol the task is blocked in - or "0" if not blocked. 157 pagemap Page table 158 stack Report full stack trace, enable via CONFIG_STACKTRACE 159 smaps An extension based on maps, showing the memory consumption of 160 each mapping and flags associated with it 161 smaps_rollup Accumulated smaps stats for all mappings of the process. This 162 can be derived from smaps, but is faster and more convenient 163 numa_maps An extension based on maps, showing the memory locality and 164 binding policy as well as mem usage (in pages) of each mapping. 165 ============= =============================================================== 166 167For example, to get the status information of a process, all you have to do is 168read the file /proc/PID/status:: 169 170 >cat /proc/self/status 171 Name: cat 172 State: R (running) 173 Tgid: 5452 174 Pid: 5452 175 PPid: 743 176 TracerPid: 0 (2.4) 177 Uid: 501 501 501 501 178 Gid: 100 100 100 100 179 FDSize: 256 180 Groups: 100 14 16 181 VmPeak: 5004 kB 182 VmSize: 5004 kB 183 VmLck: 0 kB 184 VmHWM: 476 kB 185 VmRSS: 476 kB 186 RssAnon: 352 kB 187 RssFile: 120 kB 188 RssShmem: 4 kB 189 VmData: 156 kB 190 VmStk: 88 kB 191 VmExe: 68 kB 192 VmLib: 1412 kB 193 VmPTE: 20 kb 194 VmSwap: 0 kB 195 HugetlbPages: 0 kB 196 CoreDumping: 0 197 THP_enabled: 1 198 Threads: 1 199 SigQ: 0/28578 200 SigPnd: 0000000000000000 201 ShdPnd: 0000000000000000 202 SigBlk: 0000000000000000 203 SigIgn: 0000000000000000 204 SigCgt: 0000000000000000 205 CapInh: 00000000fffffeff 206 CapPrm: 0000000000000000 207 CapEff: 0000000000000000 208 CapBnd: ffffffffffffffff 209 CapAmb: 0000000000000000 210 NoNewPrivs: 0 211 Seccomp: 0 212 Speculation_Store_Bypass: thread vulnerable 213 SpeculationIndirectBranch: conditional enabled 214 voluntary_ctxt_switches: 0 215 nonvoluntary_ctxt_switches: 1 216 217This shows you nearly the same information you would get if you viewed it with 218the ps command. In fact, ps uses the proc file system to obtain its 219information. But you get a more detailed view of the process by reading the 220file /proc/PID/status. It fields are described in table 1-2. 221 222The statm file contains more detailed information about the process 223memory usage. Its seven fields are explained in Table 1-3. The stat file 224contains detailed information about the process itself. Its fields are 225explained in Table 1-4. 226 227(for SMP CONFIG users) 228 229For making accounting scalable, RSS related information are handled in an 230asynchronous manner and the value may not be very precise. To see a precise 231snapshot of a moment, you can see /proc/<pid>/smaps file and scan page table. 232It's slow but very precise. 233 234.. table:: Table 1-2: Contents of the status files (as of 4.19) 235 236 ========================== =================================================== 237 Field Content 238 ========================== =================================================== 239 Name filename of the executable 240 Umask file mode creation mask 241 State state (R is running, S is sleeping, D is sleeping 242 in an uninterruptible wait, Z is zombie, 243 T is traced or stopped) 244 Tgid thread group ID 245 Ngid NUMA group ID (0 if none) 246 Pid process id 247 PPid process id of the parent process 248 TracerPid PID of process tracing this process (0 if not) 249 Uid Real, effective, saved set, and file system UIDs 250 Gid Real, effective, saved set, and file system GIDs 251 FDSize number of file descriptor slots currently allocated 252 Groups supplementary group list 253 NStgid descendant namespace thread group ID hierarchy 254 NSpid descendant namespace process ID hierarchy 255 NSpgid descendant namespace process group ID hierarchy 256 NSsid descendant namespace session ID hierarchy 257 VmPeak peak virtual memory size 258 VmSize total program size 259 VmLck locked memory size 260 VmPin pinned memory size 261 VmHWM peak resident set size ("high water mark") 262 VmRSS size of memory portions. It contains the three 263 following parts 264 (VmRSS = RssAnon + RssFile + RssShmem) 265 RssAnon size of resident anonymous memory 266 RssFile size of resident file mappings 267 RssShmem size of resident shmem memory (includes SysV shm, 268 mapping of tmpfs and shared anonymous mappings) 269 VmData size of private data segments 270 VmStk size of stack segments 271 VmExe size of text segment 272 VmLib size of shared library code 273 VmPTE size of page table entries 274 VmSwap amount of swap used by anonymous private data 275 (shmem swap usage is not included) 276 HugetlbPages size of hugetlb memory portions 277 CoreDumping process's memory is currently being dumped 278 (killing the process may lead to a corrupted core) 279 THP_enabled process is allowed to use THP (returns 0 when 280 PR_SET_THP_DISABLE is set on the process 281 Threads number of threads 282 SigQ number of signals queued/max. number for queue 283 SigPnd bitmap of pending signals for the thread 284 ShdPnd bitmap of shared pending signals for the process 285 SigBlk bitmap of blocked signals 286 SigIgn bitmap of ignored signals 287 SigCgt bitmap of caught signals 288 CapInh bitmap of inheritable capabilities 289 CapPrm bitmap of permitted capabilities 290 CapEff bitmap of effective capabilities 291 CapBnd bitmap of capabilities bounding set 292 CapAmb bitmap of ambient capabilities 293 NoNewPrivs no_new_privs, like prctl(PR_GET_NO_NEW_PRIV, ...) 294 Seccomp seccomp mode, like prctl(PR_GET_SECCOMP, ...) 295 Speculation_Store_Bypass speculative store bypass mitigation status 296 SpeculationIndirectBranch indirect branch speculation mode 297 Cpus_allowed mask of CPUs on which this process may run 298 Cpus_allowed_list Same as previous, but in "list format" 299 Mems_allowed mask of memory nodes allowed to this process 300 Mems_allowed_list Same as previous, but in "list format" 301 voluntary_ctxt_switches number of voluntary context switches 302 nonvoluntary_ctxt_switches number of non voluntary context switches 303 ========================== =================================================== 304 305 306.. table:: Table 1-3: Contents of the statm files (as of 2.6.8-rc3) 307 308 ======== =============================== ============================== 309 Field Content 310 ======== =============================== ============================== 311 size total program size (pages) (same as VmSize in status) 312 resident size of memory portions (pages) (same as VmRSS in status) 313 shared number of pages that are shared (i.e. backed by a file, same 314 as RssFile+RssShmem in status) 315 trs number of pages that are 'code' (not including libs; broken, 316 includes data segment) 317 lrs number of pages of library (always 0 on 2.6) 318 drs number of pages of data/stack (including libs; broken, 319 includes library text) 320 dt number of dirty pages (always 0 on 2.6) 321 ======== =============================== ============================== 322 323 324.. table:: Table 1-4: Contents of the stat files (as of 2.6.30-rc7) 325 326 ============= =============================================================== 327 Field Content 328 ============= =============================================================== 329 pid process id 330 tcomm filename of the executable 331 state state (R is running, S is sleeping, D is sleeping in an 332 uninterruptible wait, Z is zombie, T is traced or stopped) 333 ppid process id of the parent process 334 pgrp pgrp of the process 335 sid session id 336 tty_nr tty the process uses 337 tty_pgrp pgrp of the tty 338 flags task flags 339 min_flt number of minor faults 340 cmin_flt number of minor faults with child's 341 maj_flt number of major faults 342 cmaj_flt number of major faults with child's 343 utime user mode jiffies 344 stime kernel mode jiffies 345 cutime user mode jiffies with child's 346 cstime kernel mode jiffies with child's 347 priority priority level 348 nice nice level 349 num_threads number of threads 350 it_real_value (obsolete, always 0) 351 start_time time the process started after system boot 352 vsize virtual memory size 353 rss resident set memory size 354 rsslim current limit in bytes on the rss 355 start_code address above which program text can run 356 end_code address below which program text can run 357 start_stack address of the start of the main process stack 358 esp current value of ESP 359 eip current value of EIP 360 pending bitmap of pending signals 361 blocked bitmap of blocked signals 362 sigign bitmap of ignored signals 363 sigcatch bitmap of caught signals 364 0 (place holder, used to be the wchan address, 365 use /proc/PID/wchan instead) 366 0 (place holder) 367 0 (place holder) 368 exit_signal signal to send to parent thread on exit 369 task_cpu which CPU the task is scheduled on 370 rt_priority realtime priority 371 policy scheduling policy (man sched_setscheduler) 372 blkio_ticks time spent waiting for block IO 373 gtime guest time of the task in jiffies 374 cgtime guest time of the task children in jiffies 375 start_data address above which program data+bss is placed 376 end_data address below which program data+bss is placed 377 start_brk address above which program heap can be expanded with brk() 378 arg_start address above which program command line is placed 379 arg_end address below which program command line is placed 380 env_start address above which program environment is placed 381 env_end address below which program environment is placed 382 exit_code the thread's exit_code in the form reported by the waitpid 383 system call 384 ============= =============================================================== 385 386The /proc/PID/maps file contains the currently mapped memory regions and 387their access permissions. 388 389The format is:: 390 391 address perms offset dev inode pathname 392 393 08048000-08049000 r-xp 00000000 03:00 8312 /opt/test 394 08049000-0804a000 rw-p 00001000 03:00 8312 /opt/test 395 0804a000-0806b000 rw-p 00000000 00:00 0 [heap] 396 a7cb1000-a7cb2000 ---p 00000000 00:00 0 397 a7cb2000-a7eb2000 rw-p 00000000 00:00 0 398 a7eb2000-a7eb3000 ---p 00000000 00:00 0 399 a7eb3000-a7ed5000 rw-p 00000000 00:00 0 400 a7ed5000-a8008000 r-xp 00000000 03:00 4222 /lib/libc.so.6 401 a8008000-a800a000 r--p 00133000 03:00 4222 /lib/libc.so.6 402 a800a000-a800b000 rw-p 00135000 03:00 4222 /lib/libc.so.6 403 a800b000-a800e000 rw-p 00000000 00:00 0 404 a800e000-a8022000 r-xp 00000000 03:00 14462 /lib/libpthread.so.0 405 a8022000-a8023000 r--p 00013000 03:00 14462 /lib/libpthread.so.0 406 a8023000-a8024000 rw-p 00014000 03:00 14462 /lib/libpthread.so.0 407 a8024000-a8027000 rw-p 00000000 00:00 0 408 a8027000-a8043000 r-xp 00000000 03:00 8317 /lib/ld-linux.so.2 409 a8043000-a8044000 r--p 0001b000 03:00 8317 /lib/ld-linux.so.2 410 a8044000-a8045000 rw-p 0001c000 03:00 8317 /lib/ld-linux.so.2 411 aff35000-aff4a000 rw-p 00000000 00:00 0 [stack] 412 ffffe000-fffff000 r-xp 00000000 00:00 0 [vdso] 413 414where "address" is the address space in the process that it occupies, "perms" 415is a set of permissions:: 416 417 r = read 418 w = write 419 x = execute 420 s = shared 421 p = private (copy on write) 422 423"offset" is the offset into the mapping, "dev" is the device (major:minor), and 424"inode" is the inode on that device. 0 indicates that no inode is associated 425with the memory region, as the case would be with BSS (uninitialized data). 426The "pathname" shows the name associated file for this mapping. If the mapping 427is not associated with a file: 428 429 ============= ==================================== 430 [heap] the heap of the program 431 [stack] the stack of the main process 432 [vdso] the "virtual dynamic shared object", 433 the kernel system call handler 434 [anon:<name>] an anonymous mapping that has been 435 named by userspace 436 ============= ==================================== 437 438 or if empty, the mapping is anonymous. 439 440The /proc/PID/smaps is an extension based on maps, showing the memory 441consumption for each of the process's mappings. For each mapping (aka Virtual 442Memory Area, or VMA) there is a series of lines such as the following:: 443 444 08048000-080bc000 r-xp 00000000 03:02 13130 /bin/bash 445 446 Size: 1084 kB 447 KernelPageSize: 4 kB 448 MMUPageSize: 4 kB 449 Rss: 892 kB 450 Pss: 374 kB 451 Shared_Clean: 892 kB 452 Shared_Dirty: 0 kB 453 Private_Clean: 0 kB 454 Private_Dirty: 0 kB 455 Referenced: 892 kB 456 Anonymous: 0 kB 457 LazyFree: 0 kB 458 AnonHugePages: 0 kB 459 ShmemPmdMapped: 0 kB 460 Shared_Hugetlb: 0 kB 461 Private_Hugetlb: 0 kB 462 Swap: 0 kB 463 SwapPss: 0 kB 464 KernelPageSize: 4 kB 465 MMUPageSize: 4 kB 466 Locked: 0 kB 467 THPeligible: 0 468 VmFlags: rd ex mr mw me dw 469 470The first of these lines shows the same information as is displayed for the 471mapping in /proc/PID/maps. Following lines show the size of the mapping 472(size); the size of each page allocated when backing a VMA (KernelPageSize), 473which is usually the same as the size in the page table entries; the page size 474used by the MMU when backing a VMA (in most cases, the same as KernelPageSize); 475the amount of the mapping that is currently resident in RAM (RSS); the 476process' proportional share of this mapping (PSS); and the number of clean and 477dirty shared and private pages in the mapping. 478 479The "proportional set size" (PSS) of a process is the count of pages it has 480in memory, where each page is divided by the number of processes sharing it. 481So if a process has 1000 pages all to itself, and 1000 shared with one other 482process, its PSS will be 1500. 483 484Note that even a page which is part of a MAP_SHARED mapping, but has only 485a single pte mapped, i.e. is currently used by only one process, is accounted 486as private and not as shared. 487 488"Referenced" indicates the amount of memory currently marked as referenced or 489accessed. 490 491"Anonymous" shows the amount of memory that does not belong to any file. Even 492a mapping associated with a file may contain anonymous pages: when MAP_PRIVATE 493and a page is modified, the file page is replaced by a private anonymous copy. 494 495"LazyFree" shows the amount of memory which is marked by madvise(MADV_FREE). 496The memory isn't freed immediately with madvise(). It's freed in memory 497pressure if the memory is clean. Please note that the printed value might 498be lower than the real value due to optimizations used in the current 499implementation. If this is not desirable please file a bug report. 500 501"AnonHugePages" shows the ammount of memory backed by transparent hugepage. 502 503"ShmemPmdMapped" shows the ammount of shared (shmem/tmpfs) memory backed by 504huge pages. 505 506"Shared_Hugetlb" and "Private_Hugetlb" show the ammounts of memory backed by 507hugetlbfs page which is *not* counted in "RSS" or "PSS" field for historical 508reasons. And these are not included in {Shared,Private}_{Clean,Dirty} field. 509 510"Swap" shows how much would-be-anonymous memory is also used, but out on swap. 511 512For shmem mappings, "Swap" includes also the size of the mapped (and not 513replaced by copy-on-write) part of the underlying shmem object out on swap. 514"SwapPss" shows proportional swap share of this mapping. Unlike "Swap", this 515does not take into account swapped out page of underlying shmem objects. 516"Locked" indicates whether the mapping is locked in memory or not. 517"THPeligible" indicates whether the mapping is eligible for allocating THP 518pages - 1 if true, 0 otherwise. It just shows the current status. 519 520"VmFlags" field deserves a separate description. This member represents the 521kernel flags associated with the particular virtual memory area in two letter 522encoded manner. The codes are the following: 523 524 == ======================================= 525 rd readable 526 wr writeable 527 ex executable 528 sh shared 529 mr may read 530 mw may write 531 me may execute 532 ms may share 533 gd stack segment growns down 534 pf pure PFN range 535 dw disabled write to the mapped file 536 lo pages are locked in memory 537 io memory mapped I/O area 538 sr sequential read advise provided 539 rr random read advise provided 540 dc do not copy area on fork 541 de do not expand area on remapping 542 ac area is accountable 543 nr swap space is not reserved for the area 544 ht area uses huge tlb pages 545 sf synchronous page fault 546 ar architecture specific flag 547 wf wipe on fork 548 dd do not include area into core dump 549 sd soft dirty flag 550 mm mixed map area 551 hg huge page advise flag 552 nh no huge page advise flag 553 mg mergable advise flag 554 bt arm64 BTI guarded page 555 mt arm64 MTE allocation tags are enabled 556 um userfaultfd missing tracking 557 uw userfaultfd wr-protect tracking 558 == ======================================= 559 560Note that there is no guarantee that every flag and associated mnemonic will 561be present in all further kernel releases. Things get changed, the flags may 562be vanished or the reverse -- new added. Interpretation of their meaning 563might change in future as well. So each consumer of these flags has to 564follow each specific kernel version for the exact semantic. 565 566This file is only present if the CONFIG_MMU kernel configuration option is 567enabled. 568 569Note: reading /proc/PID/maps or /proc/PID/smaps is inherently racy (consistent 570output can be achieved only in the single read call). 571 572This typically manifests when doing partial reads of these files while the 573memory map is being modified. Despite the races, we do provide the following 574guarantees: 575 5761) The mapped addresses never go backwards, which implies no two 577 regions will ever overlap. 5782) If there is something at a given vaddr during the entirety of the 579 life of the smaps/maps walk, there will be some output for it. 580 581The /proc/PID/smaps_rollup file includes the same fields as /proc/PID/smaps, 582but their values are the sums of the corresponding values for all mappings of 583the process. Additionally, it contains these fields: 584 585- Pss_Anon 586- Pss_File 587- Pss_Shmem 588 589They represent the proportional shares of anonymous, file, and shmem pages, as 590described for smaps above. These fields are omitted in smaps since each 591mapping identifies the type (anon, file, or shmem) of all pages it contains. 592Thus all information in smaps_rollup can be derived from smaps, but at a 593significantly higher cost. 594 595The /proc/PID/clear_refs is used to reset the PG_Referenced and ACCESSED/YOUNG 596bits on both physical and virtual pages associated with a process, and the 597soft-dirty bit on pte (see Documentation/admin-guide/mm/soft-dirty.rst 598for details). 599To clear the bits for all the pages associated with the process:: 600 601 > echo 1 > /proc/PID/clear_refs 602 603To clear the bits for the anonymous pages associated with the process:: 604 605 > echo 2 > /proc/PID/clear_refs 606 607To clear the bits for the file mapped pages associated with the process:: 608 609 > echo 3 > /proc/PID/clear_refs 610 611To clear the soft-dirty bit:: 612 613 > echo 4 > /proc/PID/clear_refs 614 615To reset the peak resident set size ("high water mark") to the process's 616current value:: 617 618 > echo 5 > /proc/PID/clear_refs 619 620Any other value written to /proc/PID/clear_refs will have no effect. 621 622The /proc/pid/pagemap gives the PFN, which can be used to find the pageflags 623using /proc/kpageflags and number of times a page is mapped using 624/proc/kpagecount. For detailed explanation, see 625Documentation/admin-guide/mm/pagemap.rst. 626 627The /proc/pid/numa_maps is an extension based on maps, showing the memory 628locality and binding policy, as well as the memory usage (in pages) of 629each mapping. The output follows a general format where mapping details get 630summarized separated by blank spaces, one mapping per each file line:: 631 632 address policy mapping details 633 634 00400000 default file=/usr/local/bin/app mapped=1 active=0 N3=1 kernelpagesize_kB=4 635 00600000 default file=/usr/local/bin/app anon=1 dirty=1 N3=1 kernelpagesize_kB=4 636 3206000000 default file=/lib64/ld-2.12.so mapped=26 mapmax=6 N0=24 N3=2 kernelpagesize_kB=4 637 320621f000 default file=/lib64/ld-2.12.so anon=1 dirty=1 N3=1 kernelpagesize_kB=4 638 3206220000 default file=/lib64/ld-2.12.so anon=1 dirty=1 N3=1 kernelpagesize_kB=4 639 3206221000 default anon=1 dirty=1 N3=1 kernelpagesize_kB=4 640 3206800000 default file=/lib64/libc-2.12.so mapped=59 mapmax=21 active=55 N0=41 N3=18 kernelpagesize_kB=4 641 320698b000 default file=/lib64/libc-2.12.so 642 3206b8a000 default file=/lib64/libc-2.12.so anon=2 dirty=2 N3=2 kernelpagesize_kB=4 643 3206b8e000 default file=/lib64/libc-2.12.so anon=1 dirty=1 N3=1 kernelpagesize_kB=4 644 3206b8f000 default anon=3 dirty=3 active=1 N3=3 kernelpagesize_kB=4 645 7f4dc10a2000 default anon=3 dirty=3 N3=3 kernelpagesize_kB=4 646 7f4dc10b4000 default anon=2 dirty=2 active=1 N3=2 kernelpagesize_kB=4 647 7f4dc1200000 default file=/anon_hugepage\040(deleted) huge anon=1 dirty=1 N3=1 kernelpagesize_kB=2048 648 7fff335f0000 default stack anon=3 dirty=3 N3=3 kernelpagesize_kB=4 649 7fff3369d000 default mapped=1 mapmax=35 active=0 N3=1 kernelpagesize_kB=4 650 651Where: 652 653"address" is the starting address for the mapping; 654 655"policy" reports the NUMA memory policy set for the mapping (see Documentation/admin-guide/mm/numa_memory_policy.rst); 656 657"mapping details" summarizes mapping data such as mapping type, page usage counters, 658node locality page counters (N0 == node0, N1 == node1, ...) and the kernel page 659size, in KB, that is backing the mapping up. 660 6611.2 Kernel data 662--------------- 663 664Similar to the process entries, the kernel data files give information about 665the running kernel. The files used to obtain this information are contained in 666/proc and are listed in Table 1-5. Not all of these will be present in your 667system. It depends on the kernel configuration and the loaded modules, which 668files are there, and which are missing. 669 670.. table:: Table 1-5: Kernel info in /proc 671 672 ============ =============================================================== 673 File Content 674 ============ =============================================================== 675 apm Advanced power management info 676 buddyinfo Kernel memory allocator information (see text) (2.5) 677 bus Directory containing bus specific information 678 cmdline Kernel command line 679 cpuinfo Info about the CPU 680 devices Available devices (block and character) 681 dma Used DMS channels 682 filesystems Supported filesystems 683 driver Various drivers grouped here, currently rtc (2.4) 684 execdomains Execdomains, related to security (2.4) 685 fb Frame Buffer devices (2.4) 686 fs File system parameters, currently nfs/exports (2.4) 687 ide Directory containing info about the IDE subsystem 688 interrupts Interrupt usage 689 iomem Memory map (2.4) 690 ioports I/O port usage 691 irq Masks for irq to cpu affinity (2.4)(smp?) 692 isapnp ISA PnP (Plug&Play) Info (2.4) 693 kcore Kernel core image (can be ELF or A.OUT(deprecated in 2.4)) 694 kmsg Kernel messages 695 ksyms Kernel symbol table 696 loadavg Load average of last 1, 5 & 15 minutes; 697 number of processes currently runnable (running or on ready queue); 698 total number of processes in system; 699 last pid created. 700 All fields are separated by one space except "number of 701 processes currently runnable" and "total number of processes 702 in system", which are separated by a slash ('/'). Example: 703 0.61 0.61 0.55 3/828 22084 704 locks Kernel locks 705 meminfo Memory info 706 misc Miscellaneous 707 modules List of loaded modules 708 mounts Mounted filesystems 709 net Networking info (see text) 710 pagetypeinfo Additional page allocator information (see text) (2.5) 711 partitions Table of partitions known to the system 712 pci Deprecated info of PCI bus (new way -> /proc/bus/pci/, 713 decoupled by lspci (2.4) 714 rtc Real time clock 715 scsi SCSI info (see text) 716 slabinfo Slab pool info 717 softirqs softirq usage 718 stat Overall statistics 719 swaps Swap space utilization 720 sys See chapter 2 721 sysvipc Info of SysVIPC Resources (msg, sem, shm) (2.4) 722 tty Info of tty drivers 723 uptime Wall clock since boot, combined idle time of all cpus 724 version Kernel version 725 video bttv info of video resources (2.4) 726 vmallocinfo Show vmalloced areas 727 ============ =============================================================== 728 729You can, for example, check which interrupts are currently in use and what 730they are used for by looking in the file /proc/interrupts:: 731 732 > cat /proc/interrupts 733 CPU0 734 0: 8728810 XT-PIC timer 735 1: 895 XT-PIC keyboard 736 2: 0 XT-PIC cascade 737 3: 531695 XT-PIC aha152x 738 4: 2014133 XT-PIC serial 739 5: 44401 XT-PIC pcnet_cs 740 8: 2 XT-PIC rtc 741 11: 8 XT-PIC i82365 742 12: 182918 XT-PIC PS/2 Mouse 743 13: 1 XT-PIC fpu 744 14: 1232265 XT-PIC ide0 745 15: 7 XT-PIC ide1 746 NMI: 0 747 748In 2.4.* a couple of lines where added to this file LOC & ERR (this time is the 749output of a SMP machine):: 750 751 > cat /proc/interrupts 752 753 CPU0 CPU1 754 0: 1243498 1214548 IO-APIC-edge timer 755 1: 8949 8958 IO-APIC-edge keyboard 756 2: 0 0 XT-PIC cascade 757 5: 11286 10161 IO-APIC-edge soundblaster 758 8: 1 0 IO-APIC-edge rtc 759 9: 27422 27407 IO-APIC-edge 3c503 760 12: 113645 113873 IO-APIC-edge PS/2 Mouse 761 13: 0 0 XT-PIC fpu 762 14: 22491 24012 IO-APIC-edge ide0 763 15: 2183 2415 IO-APIC-edge ide1 764 17: 30564 30414 IO-APIC-level eth0 765 18: 177 164 IO-APIC-level bttv 766 NMI: 2457961 2457959 767 LOC: 2457882 2457881 768 ERR: 2155 769 770NMI is incremented in this case because every timer interrupt generates a NMI 771(Non Maskable Interrupt) which is used by the NMI Watchdog to detect lockups. 772 773LOC is the local interrupt counter of the internal APIC of every CPU. 774 775ERR is incremented in the case of errors in the IO-APIC bus (the bus that 776connects the CPUs in a SMP system. This means that an error has been detected, 777the IO-APIC automatically retry the transmission, so it should not be a big 778problem, but you should read the SMP-FAQ. 779 780In 2.6.2* /proc/interrupts was expanded again. This time the goal was for 781/proc/interrupts to display every IRQ vector in use by the system, not 782just those considered 'most important'. The new vectors are: 783 784THR 785 interrupt raised when a machine check threshold counter 786 (typically counting ECC corrected errors of memory or cache) exceeds 787 a configurable threshold. Only available on some systems. 788 789TRM 790 a thermal event interrupt occurs when a temperature threshold 791 has been exceeded for the CPU. This interrupt may also be generated 792 when the temperature drops back to normal. 793 794SPU 795 a spurious interrupt is some interrupt that was raised then lowered 796 by some IO device before it could be fully processed by the APIC. Hence 797 the APIC sees the interrupt but does not know what device it came from. 798 For this case the APIC will generate the interrupt with a IRQ vector 799 of 0xff. This might also be generated by chipset bugs. 800 801RES, CAL, TLB 802 rescheduling, call and TLB flush interrupts are 803 sent from one CPU to another per the needs of the OS. Typically, 804 their statistics are used by kernel developers and interested users to 805 determine the occurrence of interrupts of the given type. 806 807The above IRQ vectors are displayed only when relevant. For example, 808the threshold vector does not exist on x86_64 platforms. Others are 809suppressed when the system is a uniprocessor. As of this writing, only 810i386 and x86_64 platforms support the new IRQ vector displays. 811 812Of some interest is the introduction of the /proc/irq directory to 2.4. 813It could be used to set IRQ to CPU affinity. This means that you can "hook" an 814IRQ to only one CPU, or to exclude a CPU of handling IRQs. The contents of the 815irq subdir is one subdir for each IRQ, and two files; default_smp_affinity and 816prof_cpu_mask. 817 818For example:: 819 820 > ls /proc/irq/ 821 0 10 12 14 16 18 2 4 6 8 prof_cpu_mask 822 1 11 13 15 17 19 3 5 7 9 default_smp_affinity 823 > ls /proc/irq/0/ 824 smp_affinity 825 826smp_affinity is a bitmask, in which you can specify which CPUs can handle the 827IRQ. You can set it by doing:: 828 829 > echo 1 > /proc/irq/10/smp_affinity 830 831This means that only the first CPU will handle the IRQ, but you can also echo 8325 which means that only the first and third CPU can handle the IRQ. 833 834The contents of each smp_affinity file is the same by default:: 835 836 > cat /proc/irq/0/smp_affinity 837 ffffffff 838 839There is an alternate interface, smp_affinity_list which allows specifying 840a CPU range instead of a bitmask:: 841 842 > cat /proc/irq/0/smp_affinity_list 843 1024-1031 844 845The default_smp_affinity mask applies to all non-active IRQs, which are the 846IRQs which have not yet been allocated/activated, and hence which lack a 847/proc/irq/[0-9]* directory. 848 849The node file on an SMP system shows the node to which the device using the IRQ 850reports itself as being attached. This hardware locality information does not 851include information about any possible driver locality preference. 852 853prof_cpu_mask specifies which CPUs are to be profiled by the system wide 854profiler. Default value is ffffffff (all CPUs if there are only 32 of them). 855 856The way IRQs are routed is handled by the IO-APIC, and it's Round Robin 857between all the CPUs which are allowed to handle it. As usual the kernel has 858more info than you and does a better job than you, so the defaults are the 859best choice for almost everyone. [Note this applies only to those IO-APIC's 860that support "Round Robin" interrupt distribution.] 861 862There are three more important subdirectories in /proc: net, scsi, and sys. 863The general rule is that the contents, or even the existence of these 864directories, depend on your kernel configuration. If SCSI is not enabled, the 865directory scsi may not exist. The same is true with the net, which is there 866only when networking support is present in the running kernel. 867 868The slabinfo file gives information about memory usage at the slab level. 869Linux uses slab pools for memory management above page level in version 2.2. 870Commonly used objects have their own slab pool (such as network buffers, 871directory cache, and so on). 872 873:: 874 875 > cat /proc/buddyinfo 876 877 Node 0, zone DMA 0 4 5 4 4 3 ... 878 Node 0, zone Normal 1 0 0 1 101 8 ... 879 Node 0, zone HighMem 2 0 0 1 1 0 ... 880 881External fragmentation is a problem under some workloads, and buddyinfo is a 882useful tool for helping diagnose these problems. Buddyinfo will give you a 883clue as to how big an area you can safely allocate, or why a previous 884allocation failed. 885 886Each column represents the number of pages of a certain order which are 887available. In this case, there are 0 chunks of 2^0*PAGE_SIZE available in 888ZONE_DMA, 4 chunks of 2^1*PAGE_SIZE in ZONE_DMA, 101 chunks of 2^4*PAGE_SIZE 889available in ZONE_NORMAL, etc... 890 891More information relevant to external fragmentation can be found in 892pagetypeinfo:: 893 894 > cat /proc/pagetypeinfo 895 Page block order: 9 896 Pages per block: 512 897 898 Free pages count per migrate type at order 0 1 2 3 4 5 6 7 8 9 10 899 Node 0, zone DMA, type Unmovable 0 0 0 1 1 1 1 1 1 1 0 900 Node 0, zone DMA, type Reclaimable 0 0 0 0 0 0 0 0 0 0 0 901 Node 0, zone DMA, type Movable 1 1 2 1 2 1 1 0 1 0 2 902 Node 0, zone DMA, type Reserve 0 0 0 0 0 0 0 0 0 1 0 903 Node 0, zone DMA, type Isolate 0 0 0 0 0 0 0 0 0 0 0 904 Node 0, zone DMA32, type Unmovable 103 54 77 1 1 1 11 8 7 1 9 905 Node 0, zone DMA32, type Reclaimable 0 0 2 1 0 0 0 0 1 0 0 906 Node 0, zone DMA32, type Movable 169 152 113 91 77 54 39 13 6 1 452 907 Node 0, zone DMA32, type Reserve 1 2 2 2 2 0 1 1 1 1 0 908 Node 0, zone DMA32, type Isolate 0 0 0 0 0 0 0 0 0 0 0 909 910 Number of blocks type Unmovable Reclaimable Movable Reserve Isolate 911 Node 0, zone DMA 2 0 5 1 0 912 Node 0, zone DMA32 41 6 967 2 0 913 914Fragmentation avoidance in the kernel works by grouping pages of different 915migrate types into the same contiguous regions of memory called page blocks. 916A page block is typically the size of the default hugepage size, e.g. 2MB on 917X86-64. By keeping pages grouped based on their ability to move, the kernel 918can reclaim pages within a page block to satisfy a high-order allocation. 919 920The pagetypinfo begins with information on the size of a page block. It 921then gives the same type of information as buddyinfo except broken down 922by migrate-type and finishes with details on how many page blocks of each 923type exist. 924 925If min_free_kbytes has been tuned correctly (recommendations made by hugeadm 926from libhugetlbfs https://github.com/libhugetlbfs/libhugetlbfs/), one can 927make an estimate of the likely number of huge pages that can be allocated 928at a given point in time. All the "Movable" blocks should be allocatable 929unless memory has been mlock()'d. Some of the Reclaimable blocks should 930also be allocatable although a lot of filesystem metadata may have to be 931reclaimed to achieve this. 932 933 934meminfo 935~~~~~~~ 936 937Provides information about distribution and utilization of memory. This 938varies by architecture and compile options. Some of the counters reported 939here overlap. The memory reported by the non overlapping counters may not 940add up to the overall memory usage and the difference for some workloads 941can be substantial. In many cases there are other means to find out 942additional memory using subsystem specific interfaces, for instance 943/proc/net/sockstat for TCP memory allocations. 944 945Example output. You may not have all of these fields. 946 947:: 948 949 > cat /proc/meminfo 950 951 MemTotal: 32858820 kB 952 MemFree: 21001236 kB 953 MemAvailable: 27214312 kB 954 Buffers: 581092 kB 955 Cached: 5587612 kB 956 SwapCached: 0 kB 957 Active: 3237152 kB 958 Inactive: 7586256 kB 959 Active(anon): 94064 kB 960 Inactive(anon): 4570616 kB 961 Active(file): 3143088 kB 962 Inactive(file): 3015640 kB 963 Unevictable: 0 kB 964 Mlocked: 0 kB 965 SwapTotal: 0 kB 966 SwapFree: 0 kB 967 Dirty: 12 kB 968 Writeback: 0 kB 969 AnonPages: 4654780 kB 970 Mapped: 266244 kB 971 Shmem: 9976 kB 972 KReclaimable: 517708 kB 973 Slab: 660044 kB 974 SReclaimable: 517708 kB 975 SUnreclaim: 142336 kB 976 KernelStack: 11168 kB 977 PageTables: 20540 kB 978 NFS_Unstable: 0 kB 979 Bounce: 0 kB 980 WritebackTmp: 0 kB 981 CommitLimit: 16429408 kB 982 Committed_AS: 7715148 kB 983 VmallocTotal: 34359738367 kB 984 VmallocUsed: 40444 kB 985 VmallocChunk: 0 kB 986 Percpu: 29312 kB 987 HardwareCorrupted: 0 kB 988 AnonHugePages: 4149248 kB 989 ShmemHugePages: 0 kB 990 ShmemPmdMapped: 0 kB 991 FileHugePages: 0 kB 992 FilePmdMapped: 0 kB 993 CmaTotal: 0 kB 994 CmaFree: 0 kB 995 HugePages_Total: 0 996 HugePages_Free: 0 997 HugePages_Rsvd: 0 998 HugePages_Surp: 0 999 Hugepagesize: 2048 kB 1000 Hugetlb: 0 kB 1001 DirectMap4k: 401152 kB 1002 DirectMap2M: 10008576 kB 1003 DirectMap1G: 24117248 kB 1004 1005MemTotal 1006 Total usable RAM (i.e. physical RAM minus a few reserved 1007 bits and the kernel binary code) 1008MemFree 1009 Total free RAM. On highmem systems, the sum of LowFree+HighFree 1010MemAvailable 1011 An estimate of how much memory is available for starting new 1012 applications, without swapping. Calculated from MemFree, 1013 SReclaimable, the size of the file LRU lists, and the low 1014 watermarks in each zone. 1015 The estimate takes into account that the system needs some 1016 page cache to function well, and that not all reclaimable 1017 slab will be reclaimable, due to items being in use. The 1018 impact of those factors will vary from system to system. 1019Buffers 1020 Relatively temporary storage for raw disk blocks 1021 shouldn't get tremendously large (20MB or so) 1022Cached 1023 In-memory cache for files read from the disk (the 1024 pagecache) as well as tmpfs & shmem. 1025 Doesn't include SwapCached. 1026SwapCached 1027 Memory that once was swapped out, is swapped back in but 1028 still also is in the swapfile (if memory is needed it 1029 doesn't need to be swapped out AGAIN because it is already 1030 in the swapfile. This saves I/O) 1031Active 1032 Memory that has been used more recently and usually not 1033 reclaimed unless absolutely necessary. 1034Inactive 1035 Memory which has been less recently used. It is more 1036 eligible to be reclaimed for other purposes 1037Unevictable 1038 Memory allocated for userspace which cannot be reclaimed, such 1039 as mlocked pages, ramfs backing pages, secret memfd pages etc. 1040Mlocked 1041 Memory locked with mlock(). 1042HighTotal, HighFree 1043 Highmem is all memory above ~860MB of physical memory. 1044 Highmem areas are for use by userspace programs, or 1045 for the pagecache. The kernel must use tricks to access 1046 this memory, making it slower to access than lowmem. 1047LowTotal, LowFree 1048 Lowmem is memory which can be used for everything that 1049 highmem can be used for, but it is also available for the 1050 kernel's use for its own data structures. Among many 1051 other things, it is where everything from the Slab is 1052 allocated. Bad things happen when you're out of lowmem. 1053SwapTotal 1054 total amount of swap space available 1055SwapFree 1056 Memory which has been evicted from RAM, and is temporarily 1057 on the disk 1058Dirty 1059 Memory which is waiting to get written back to the disk 1060Writeback 1061 Memory which is actively being written back to the disk 1062AnonPages 1063 Non-file backed pages mapped into userspace page tables 1064Mapped 1065 files which have been mmaped, such as libraries 1066Shmem 1067 Total memory used by shared memory (shmem) and tmpfs 1068KReclaimable 1069 Kernel allocations that the kernel will attempt to reclaim 1070 under memory pressure. Includes SReclaimable (below), and other 1071 direct allocations with a shrinker. 1072Slab 1073 in-kernel data structures cache 1074SReclaimable 1075 Part of Slab, that might be reclaimed, such as caches 1076SUnreclaim 1077 Part of Slab, that cannot be reclaimed on memory pressure 1078KernelStack 1079 Memory consumed by the kernel stacks of all tasks 1080PageTables 1081 Memory consumed by userspace page tables 1082NFS_Unstable 1083 Always zero. Previous counted pages which had been written to 1084 the server, but has not been committed to stable storage. 1085Bounce 1086 Memory used for block device "bounce buffers" 1087WritebackTmp 1088 Memory used by FUSE for temporary writeback buffers 1089CommitLimit 1090 Based on the overcommit ratio ('vm.overcommit_ratio'), 1091 this is the total amount of memory currently available to 1092 be allocated on the system. This limit is only adhered to 1093 if strict overcommit accounting is enabled (mode 2 in 1094 'vm.overcommit_memory'). 1095 1096 The CommitLimit is calculated with the following formula:: 1097 1098 CommitLimit = ([total RAM pages] - [total huge TLB pages]) * 1099 overcommit_ratio / 100 + [total swap pages] 1100 1101 For example, on a system with 1G of physical RAM and 7G 1102 of swap with a `vm.overcommit_ratio` of 30 it would 1103 yield a CommitLimit of 7.3G. 1104 1105 For more details, see the memory overcommit documentation 1106 in vm/overcommit-accounting. 1107Committed_AS 1108 The amount of memory presently allocated on the system. 1109 The committed memory is a sum of all of the memory which 1110 has been allocated by processes, even if it has not been 1111 "used" by them as of yet. A process which malloc()'s 1G 1112 of memory, but only touches 300M of it will show up as 1113 using 1G. This 1G is memory which has been "committed" to 1114 by the VM and can be used at any time by the allocating 1115 application. With strict overcommit enabled on the system 1116 (mode 2 in 'vm.overcommit_memory'), allocations which would 1117 exceed the CommitLimit (detailed above) will not be permitted. 1118 This is useful if one needs to guarantee that processes will 1119 not fail due to lack of memory once that memory has been 1120 successfully allocated. 1121VmallocTotal 1122 total size of vmalloc virtual address space 1123VmallocUsed 1124 amount of vmalloc area which is used 1125VmallocChunk 1126 largest contiguous block of vmalloc area which is free 1127Percpu 1128 Memory allocated to the percpu allocator used to back percpu 1129 allocations. This stat excludes the cost of metadata. 1130HardwareCorrupted 1131 The amount of RAM/memory in KB, the kernel identifies as 1132 corrupted. 1133AnonHugePages 1134 Non-file backed huge pages mapped into userspace page tables 1135ShmemHugePages 1136 Memory used by shared memory (shmem) and tmpfs allocated 1137 with huge pages 1138ShmemPmdMapped 1139 Shared memory mapped into userspace with huge pages 1140FileHugePages 1141 Memory used for filesystem data (page cache) allocated 1142 with huge pages 1143FilePmdMapped 1144 Page cache mapped into userspace with huge pages 1145CmaTotal 1146 Memory reserved for the Contiguous Memory Allocator (CMA) 1147CmaFree 1148 Free remaining memory in the CMA reserves 1149HugePages_Total, HugePages_Free, HugePages_Rsvd, HugePages_Surp, Hugepagesize, Hugetlb 1150 See Documentation/admin-guide/mm/hugetlbpage.rst. 1151DirectMap4k, DirectMap2M, DirectMap1G 1152 Breakdown of page table sizes used in the kernel's 1153 identity mapping of RAM 1154 1155vmallocinfo 1156~~~~~~~~~~~ 1157 1158Provides information about vmalloced/vmaped areas. One line per area, 1159containing the virtual address range of the area, size in bytes, 1160caller information of the creator, and optional information depending 1161on the kind of area: 1162 1163 ========== =================================================== 1164 pages=nr number of pages 1165 phys=addr if a physical address was specified 1166 ioremap I/O mapping (ioremap() and friends) 1167 vmalloc vmalloc() area 1168 vmap vmap()ed pages 1169 user VM_USERMAP area 1170 vpages buffer for pages pointers was vmalloced (huge area) 1171 N<node>=nr (Only on NUMA kernels) 1172 Number of pages allocated on memory node <node> 1173 ========== =================================================== 1174 1175:: 1176 1177 > cat /proc/vmallocinfo 1178 0xffffc20000000000-0xffffc20000201000 2101248 alloc_large_system_hash+0x204 ... 1179 /0x2c0 pages=512 vmalloc N0=128 N1=128 N2=128 N3=128 1180 0xffffc20000201000-0xffffc20000302000 1052672 alloc_large_system_hash+0x204 ... 1181 /0x2c0 pages=256 vmalloc N0=64 N1=64 N2=64 N3=64 1182 0xffffc20000302000-0xffffc20000304000 8192 acpi_tb_verify_table+0x21/0x4f... 1183 phys=7fee8000 ioremap 1184 0xffffc20000304000-0xffffc20000307000 12288 acpi_tb_verify_table+0x21/0x4f... 1185 phys=7fee7000 ioremap 1186 0xffffc2000031d000-0xffffc2000031f000 8192 init_vdso_vars+0x112/0x210 1187 0xffffc2000031f000-0xffffc2000032b000 49152 cramfs_uncompress_init+0x2e ... 1188 /0x80 pages=11 vmalloc N0=3 N1=3 N2=2 N3=3 1189 0xffffc2000033a000-0xffffc2000033d000 12288 sys_swapon+0x640/0xac0 ... 1190 pages=2 vmalloc N1=2 1191 0xffffc20000347000-0xffffc2000034c000 20480 xt_alloc_table_info+0xfe ... 1192 /0x130 [x_tables] pages=4 vmalloc N0=4 1193 0xffffffffa0000000-0xffffffffa000f000 61440 sys_init_module+0xc27/0x1d00 ... 1194 pages=14 vmalloc N2=14 1195 0xffffffffa000f000-0xffffffffa0014000 20480 sys_init_module+0xc27/0x1d00 ... 1196 pages=4 vmalloc N1=4 1197 0xffffffffa0014000-0xffffffffa0017000 12288 sys_init_module+0xc27/0x1d00 ... 1198 pages=2 vmalloc N1=2 1199 0xffffffffa0017000-0xffffffffa0022000 45056 sys_init_module+0xc27/0x1d00 ... 1200 pages=10 vmalloc N0=10 1201 1202 1203softirqs 1204~~~~~~~~ 1205 1206Provides counts of softirq handlers serviced since boot time, for each CPU. 1207 1208:: 1209 1210 > cat /proc/softirqs 1211 CPU0 CPU1 CPU2 CPU3 1212 HI: 0 0 0 0 1213 TIMER: 27166 27120 27097 27034 1214 NET_TX: 0 0 0 17 1215 NET_RX: 42 0 0 39 1216 BLOCK: 0 0 107 1121 1217 TASKLET: 0 0 0 290 1218 SCHED: 27035 26983 26971 26746 1219 HRTIMER: 0 0 0 0 1220 RCU: 1678 1769 2178 2250 1221 1222 12231.3 IDE devices in /proc/ide 1224---------------------------- 1225 1226The subdirectory /proc/ide contains information about all IDE devices of which 1227the kernel is aware. There is one subdirectory for each IDE controller, the 1228file drivers and a link for each IDE device, pointing to the device directory 1229in the controller specific subtree. 1230 1231The file 'drivers' contains general information about the drivers used for the 1232IDE devices:: 1233 1234 > cat /proc/ide/drivers 1235 ide-cdrom version 4.53 1236 ide-disk version 1.08 1237 1238More detailed information can be found in the controller specific 1239subdirectories. These are named ide0, ide1 and so on. Each of these 1240directories contains the files shown in table 1-6. 1241 1242 1243.. table:: Table 1-6: IDE controller info in /proc/ide/ide? 1244 1245 ======= ======================================= 1246 File Content 1247 ======= ======================================= 1248 channel IDE channel (0 or 1) 1249 config Configuration (only for PCI/IDE bridge) 1250 mate Mate name 1251 model Type/Chipset of IDE controller 1252 ======= ======================================= 1253 1254Each device connected to a controller has a separate subdirectory in the 1255controllers directory. The files listed in table 1-7 are contained in these 1256directories. 1257 1258 1259.. table:: Table 1-7: IDE device information 1260 1261 ================ ========================================== 1262 File Content 1263 ================ ========================================== 1264 cache The cache 1265 capacity Capacity of the medium (in 512Byte blocks) 1266 driver driver and version 1267 geometry physical and logical geometry 1268 identify device identify block 1269 media media type 1270 model device identifier 1271 settings device setup 1272 smart_thresholds IDE disk management thresholds 1273 smart_values IDE disk management values 1274 ================ ========================================== 1275 1276The most interesting file is ``settings``. This file contains a nice 1277overview of the drive parameters:: 1278 1279 # cat /proc/ide/ide0/hda/settings 1280 name value min max mode 1281 ---- ----- --- --- ---- 1282 bios_cyl 526 0 65535 rw 1283 bios_head 255 0 255 rw 1284 bios_sect 63 0 63 rw 1285 breada_readahead 4 0 127 rw 1286 bswap 0 0 1 r 1287 file_readahead 72 0 2097151 rw 1288 io_32bit 0 0 3 rw 1289 keepsettings 0 0 1 rw 1290 max_kb_per_request 122 1 127 rw 1291 multcount 0 0 8 rw 1292 nice1 1 0 1 rw 1293 nowerr 0 0 1 rw 1294 pio_mode write-only 0 255 w 1295 slow 0 0 1 rw 1296 unmaskirq 0 0 1 rw 1297 using_dma 0 0 1 rw 1298 1299 13001.4 Networking info in /proc/net 1301-------------------------------- 1302 1303The subdirectory /proc/net follows the usual pattern. Table 1-8 shows the 1304additional values you get for IP version 6 if you configure the kernel to 1305support this. Table 1-9 lists the files and their meaning. 1306 1307 1308.. table:: Table 1-8: IPv6 info in /proc/net 1309 1310 ========== ===================================================== 1311 File Content 1312 ========== ===================================================== 1313 udp6 UDP sockets (IPv6) 1314 tcp6 TCP sockets (IPv6) 1315 raw6 Raw device statistics (IPv6) 1316 igmp6 IP multicast addresses, which this host joined (IPv6) 1317 if_inet6 List of IPv6 interface addresses 1318 ipv6_route Kernel routing table for IPv6 1319 rt6_stats Global IPv6 routing tables statistics 1320 sockstat6 Socket statistics (IPv6) 1321 snmp6 Snmp data (IPv6) 1322 ========== ===================================================== 1323 1324.. table:: Table 1-9: Network info in /proc/net 1325 1326 ============= ================================================================ 1327 File Content 1328 ============= ================================================================ 1329 arp Kernel ARP table 1330 dev network devices with statistics 1331 dev_mcast the Layer2 multicast groups a device is listening too 1332 (interface index, label, number of references, number of bound 1333 addresses). 1334 dev_stat network device status 1335 ip_fwchains Firewall chain linkage 1336 ip_fwnames Firewall chain names 1337 ip_masq Directory containing the masquerading tables 1338 ip_masquerade Major masquerading table 1339 netstat Network statistics 1340 raw raw device statistics 1341 route Kernel routing table 1342 rpc Directory containing rpc info 1343 rt_cache Routing cache 1344 snmp SNMP data 1345 sockstat Socket statistics 1346 tcp TCP sockets 1347 udp UDP sockets 1348 unix UNIX domain sockets 1349 wireless Wireless interface data (Wavelan etc) 1350 igmp IP multicast addresses, which this host joined 1351 psched Global packet scheduler parameters. 1352 netlink List of PF_NETLINK sockets 1353 ip_mr_vifs List of multicast virtual interfaces 1354 ip_mr_cache List of multicast routing cache 1355 ============= ================================================================ 1356 1357You can use this information to see which network devices are available in 1358your system and how much traffic was routed over those devices:: 1359 1360 > cat /proc/net/dev 1361 Inter-|Receive |[... 1362 face |bytes packets errs drop fifo frame compressed multicast|[... 1363 lo: 908188 5596 0 0 0 0 0 0 [... 1364 ppp0:15475140 20721 410 0 0 410 0 0 [... 1365 eth0: 614530 7085 0 0 0 0 0 1 [... 1366 1367 ...] Transmit 1368 ...] bytes packets errs drop fifo colls carrier compressed 1369 ...] 908188 5596 0 0 0 0 0 0 1370 ...] 1375103 17405 0 0 0 0 0 0 1371 ...] 1703981 5535 0 0 0 3 0 0 1372 1373In addition, each Channel Bond interface has its own directory. For 1374example, the bond0 device will have a directory called /proc/net/bond0/. 1375It will contain information that is specific to that bond, such as the 1376current slaves of the bond, the link status of the slaves, and how 1377many times the slaves link has failed. 1378 13791.5 SCSI info 1380------------- 1381 1382If you have a SCSI host adapter in your system, you'll find a subdirectory 1383named after the driver for this adapter in /proc/scsi. You'll also see a list 1384of all recognized SCSI devices in /proc/scsi:: 1385 1386 >cat /proc/scsi/scsi 1387 Attached devices: 1388 Host: scsi0 Channel: 00 Id: 00 Lun: 00 1389 Vendor: IBM Model: DGHS09U Rev: 03E0 1390 Type: Direct-Access ANSI SCSI revision: 03 1391 Host: scsi0 Channel: 00 Id: 06 Lun: 00 1392 Vendor: PIONEER Model: CD-ROM DR-U06S Rev: 1.04 1393 Type: CD-ROM ANSI SCSI revision: 02 1394 1395 1396The directory named after the driver has one file for each adapter found in 1397the system. These files contain information about the controller, including 1398the used IRQ and the IO address range. The amount of information shown is 1399dependent on the adapter you use. The example shows the output for an Adaptec 1400AHA-2940 SCSI adapter:: 1401 1402 > cat /proc/scsi/aic7xxx/0 1403 1404 Adaptec AIC7xxx driver version: 5.1.19/3.2.4 1405 Compile Options: 1406 TCQ Enabled By Default : Disabled 1407 AIC7XXX_PROC_STATS : Disabled 1408 AIC7XXX_RESET_DELAY : 5 1409 Adapter Configuration: 1410 SCSI Adapter: Adaptec AHA-294X Ultra SCSI host adapter 1411 Ultra Wide Controller 1412 PCI MMAPed I/O Base: 0xeb001000 1413 Adapter SEEPROM Config: SEEPROM found and used. 1414 Adaptec SCSI BIOS: Enabled 1415 IRQ: 10 1416 SCBs: Active 0, Max Active 2, 1417 Allocated 15, HW 16, Page 255 1418 Interrupts: 160328 1419 BIOS Control Word: 0x18b6 1420 Adapter Control Word: 0x005b 1421 Extended Translation: Enabled 1422 Disconnect Enable Flags: 0xffff 1423 Ultra Enable Flags: 0x0001 1424 Tag Queue Enable Flags: 0x0000 1425 Ordered Queue Tag Flags: 0x0000 1426 Default Tag Queue Depth: 8 1427 Tagged Queue By Device array for aic7xxx host instance 0: 1428 {255,255,255,255,255,255,255,255,255,255,255,255,255,255,255,255} 1429 Actual queue depth per device for aic7xxx host instance 0: 1430 {1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1} 1431 Statistics: 1432 (scsi0:0:0:0) 1433 Device using Wide/Sync transfers at 40.0 MByte/sec, offset 8 1434 Transinfo settings: current(12/8/1/0), goal(12/8/1/0), user(12/15/1/0) 1435 Total transfers 160151 (74577 reads and 85574 writes) 1436 (scsi0:0:6:0) 1437 Device using Narrow/Sync transfers at 5.0 MByte/sec, offset 15 1438 Transinfo settings: current(50/15/0/0), goal(50/15/0/0), user(50/15/0/0) 1439 Total transfers 0 (0 reads and 0 writes) 1440 1441 14421.6 Parallel port info in /proc/parport 1443--------------------------------------- 1444 1445The directory /proc/parport contains information about the parallel ports of 1446your system. It has one subdirectory for each port, named after the port 1447number (0,1,2,...). 1448 1449These directories contain the four files shown in Table 1-10. 1450 1451 1452.. table:: Table 1-10: Files in /proc/parport 1453 1454 ========= ==================================================================== 1455 File Content 1456 ========= ==================================================================== 1457 autoprobe Any IEEE-1284 device ID information that has been acquired. 1458 devices list of the device drivers using that port. A + will appear by the 1459 name of the device currently using the port (it might not appear 1460 against any). 1461 hardware Parallel port's base address, IRQ line and DMA channel. 1462 irq IRQ that parport is using for that port. This is in a separate 1463 file to allow you to alter it by writing a new value in (IRQ 1464 number or none). 1465 ========= ==================================================================== 1466 14671.7 TTY info in /proc/tty 1468------------------------- 1469 1470Information about the available and actually used tty's can be found in the 1471directory /proc/tty. You'll find entries for drivers and line disciplines in 1472this directory, as shown in Table 1-11. 1473 1474 1475.. table:: Table 1-11: Files in /proc/tty 1476 1477 ============= ============================================== 1478 File Content 1479 ============= ============================================== 1480 drivers list of drivers and their usage 1481 ldiscs registered line disciplines 1482 driver/serial usage statistic and status of single tty lines 1483 ============= ============================================== 1484 1485To see which tty's are currently in use, you can simply look into the file 1486/proc/tty/drivers:: 1487 1488 > cat /proc/tty/drivers 1489 pty_slave /dev/pts 136 0-255 pty:slave 1490 pty_master /dev/ptm 128 0-255 pty:master 1491 pty_slave /dev/ttyp 3 0-255 pty:slave 1492 pty_master /dev/pty 2 0-255 pty:master 1493 serial /dev/cua 5 64-67 serial:callout 1494 serial /dev/ttyS 4 64-67 serial 1495 /dev/tty0 /dev/tty0 4 0 system:vtmaster 1496 /dev/ptmx /dev/ptmx 5 2 system 1497 /dev/console /dev/console 5 1 system:console 1498 /dev/tty /dev/tty 5 0 system:/dev/tty 1499 unknown /dev/tty 4 1-63 console 1500 1501 15021.8 Miscellaneous kernel statistics in /proc/stat 1503------------------------------------------------- 1504 1505Various pieces of information about kernel activity are available in the 1506/proc/stat file. All of the numbers reported in this file are aggregates 1507since the system first booted. For a quick look, simply cat the file:: 1508 1509 > cat /proc/stat 1510 cpu 2255 34 2290 22625563 6290 127 456 0 0 0 1511 cpu0 1132 34 1441 11311718 3675 127 438 0 0 0 1512 cpu1 1123 0 849 11313845 2614 0 18 0 0 0 1513 intr 114930548 113199788 3 0 5 263 0 4 [... lots more numbers ...] 1514 ctxt 1990473 1515 btime 1062191376 1516 processes 2915 1517 procs_running 1 1518 procs_blocked 0 1519 softirq 183433 0 21755 12 39 1137 231 21459 2263 1520 1521The very first "cpu" line aggregates the numbers in all of the other "cpuN" 1522lines. These numbers identify the amount of time the CPU has spent performing 1523different kinds of work. Time units are in USER_HZ (typically hundredths of a 1524second). The meanings of the columns are as follows, from left to right: 1525 1526- user: normal processes executing in user mode 1527- nice: niced processes executing in user mode 1528- system: processes executing in kernel mode 1529- idle: twiddling thumbs 1530- iowait: In a word, iowait stands for waiting for I/O to complete. But there 1531 are several problems: 1532 1533 1. CPU will not wait for I/O to complete, iowait is the time that a task is 1534 waiting for I/O to complete. When CPU goes into idle state for 1535 outstanding task I/O, another task will be scheduled on this CPU. 1536 2. In a multi-core CPU, the task waiting for I/O to complete is not running 1537 on any CPU, so the iowait of each CPU is difficult to calculate. 1538 3. The value of iowait field in /proc/stat will decrease in certain 1539 conditions. 1540 1541 So, the iowait is not reliable by reading from /proc/stat. 1542- irq: servicing interrupts 1543- softirq: servicing softirqs 1544- steal: involuntary wait 1545- guest: running a normal guest 1546- guest_nice: running a niced guest 1547 1548The "intr" line gives counts of interrupts serviced since boot time, for each 1549of the possible system interrupts. The first column is the total of all 1550interrupts serviced including unnumbered architecture specific interrupts; 1551each subsequent column is the total for that particular numbered interrupt. 1552Unnumbered interrupts are not shown, only summed into the total. 1553 1554The "ctxt" line gives the total number of context switches across all CPUs. 1555 1556The "btime" line gives the time at which the system booted, in seconds since 1557the Unix epoch. 1558 1559The "processes" line gives the number of processes and threads created, which 1560includes (but is not limited to) those created by calls to the fork() and 1561clone() system calls. 1562 1563The "procs_running" line gives the total number of threads that are 1564running or ready to run (i.e., the total number of runnable threads). 1565 1566The "procs_blocked" line gives the number of processes currently blocked, 1567waiting for I/O to complete. 1568 1569The "softirq" line gives counts of softirqs serviced since boot time, for each 1570of the possible system softirqs. The first column is the total of all 1571softirqs serviced; each subsequent column is the total for that particular 1572softirq. 1573 1574 15751.9 Ext4 file system parameters 1576------------------------------- 1577 1578Information about mounted ext4 file systems can be found in 1579/proc/fs/ext4. Each mounted filesystem will have a directory in 1580/proc/fs/ext4 based on its device name (i.e., /proc/fs/ext4/hdc or 1581/proc/fs/ext4/dm-0). The files in each per-device directory are shown 1582in Table 1-12, below. 1583 1584.. table:: Table 1-12: Files in /proc/fs/ext4/<devname> 1585 1586 ============== ========================================================== 1587 File Content 1588 mb_groups details of multiblock allocator buddy cache of free blocks 1589 ============== ========================================================== 1590 15911.10 /proc/consoles 1592------------------- 1593Shows registered system console lines. 1594 1595To see which character device lines are currently used for the system console 1596/dev/console, you may simply look into the file /proc/consoles:: 1597 1598 > cat /proc/consoles 1599 tty0 -WU (ECp) 4:7 1600 ttyS0 -W- (Ep) 4:64 1601 1602The columns are: 1603 1604+--------------------+-------------------------------------------------------+ 1605| device | name of the device | 1606+====================+=======================================================+ 1607| operations | * R = can do read operations | 1608| | * W = can do write operations | 1609| | * U = can do unblank | 1610+--------------------+-------------------------------------------------------+ 1611| flags | * E = it is enabled | 1612| | * C = it is preferred console | 1613| | * B = it is primary boot console | 1614| | * p = it is used for printk buffer | 1615| | * b = it is not a TTY but a Braille device | 1616| | * a = it is safe to use when cpu is offline | 1617+--------------------+-------------------------------------------------------+ 1618| major:minor | major and minor number of the device separated by a | 1619| | colon | 1620+--------------------+-------------------------------------------------------+ 1621 1622Summary 1623------- 1624 1625The /proc file system serves information about the running system. It not only 1626allows access to process data but also allows you to request the kernel status 1627by reading files in the hierarchy. 1628 1629The directory structure of /proc reflects the types of information and makes 1630it easy, if not obvious, where to look for specific data. 1631 1632Chapter 2: Modifying System Parameters 1633====================================== 1634 1635In This Chapter 1636--------------- 1637 1638* Modifying kernel parameters by writing into files found in /proc/sys 1639* Exploring the files which modify certain parameters 1640* Review of the /proc/sys file tree 1641 1642------------------------------------------------------------------------------ 1643 1644A very interesting part of /proc is the directory /proc/sys. This is not only 1645a source of information, it also allows you to change parameters within the 1646kernel. Be very careful when attempting this. You can optimize your system, 1647but you can also cause it to crash. Never alter kernel parameters on a 1648production system. Set up a development machine and test to make sure that 1649everything works the way you want it to. You may have no alternative but to 1650reboot the machine once an error has been made. 1651 1652To change a value, simply echo the new value into the file. 1653You need to be root to do this. You can create your own boot script 1654to perform this every time your system boots. 1655 1656The files in /proc/sys can be used to fine tune and monitor miscellaneous and 1657general things in the operation of the Linux kernel. Since some of the files 1658can inadvertently disrupt your system, it is advisable to read both 1659documentation and source before actually making adjustments. In any case, be 1660very careful when writing to any of these files. The entries in /proc may 1661change slightly between the 2.1.* and the 2.2 kernel, so if there is any doubt 1662review the kernel documentation in the directory /usr/src/linux/Documentation. 1663This chapter is heavily based on the documentation included in the pre 2.2 1664kernels, and became part of it in version 2.2.1 of the Linux kernel. 1665 1666Please see: Documentation/admin-guide/sysctl/ directory for descriptions of these 1667entries. 1668 1669Summary 1670------- 1671 1672Certain aspects of kernel behavior can be modified at runtime, without the 1673need to recompile the kernel, or even to reboot the system. The files in the 1674/proc/sys tree can not only be read, but also modified. You can use the echo 1675command to write value into these files, thereby changing the default settings 1676of the kernel. 1677 1678 1679Chapter 3: Per-process Parameters 1680================================= 1681 16823.1 /proc/<pid>/oom_adj & /proc/<pid>/oom_score_adj- Adjust the oom-killer score 1683-------------------------------------------------------------------------------- 1684 1685These files can be used to adjust the badness heuristic used to select which 1686process gets killed in out of memory (oom) conditions. 1687 1688The badness heuristic assigns a value to each candidate task ranging from 0 1689(never kill) to 1000 (always kill) to determine which process is targeted. The 1690units are roughly a proportion along that range of allowed memory the process 1691may allocate from based on an estimation of its current memory and swap use. 1692For example, if a task is using all allowed memory, its badness score will be 16931000. If it is using half of its allowed memory, its score will be 500. 1694 1695The amount of "allowed" memory depends on the context in which the oom killer 1696was called. If it is due to the memory assigned to the allocating task's cpuset 1697being exhausted, the allowed memory represents the set of mems assigned to that 1698cpuset. If it is due to a mempolicy's node(s) being exhausted, the allowed 1699memory represents the set of mempolicy nodes. If it is due to a memory 1700limit (or swap limit) being reached, the allowed memory is that configured 1701limit. Finally, if it is due to the entire system being out of memory, the 1702allowed memory represents all allocatable resources. 1703 1704The value of /proc/<pid>/oom_score_adj is added to the badness score before it 1705is used to determine which task to kill. Acceptable values range from -1000 1706(OOM_SCORE_ADJ_MIN) to +1000 (OOM_SCORE_ADJ_MAX). This allows userspace to 1707polarize the preference for oom killing either by always preferring a certain 1708task or completely disabling it. The lowest possible value, -1000, is 1709equivalent to disabling oom killing entirely for that task since it will always 1710report a badness score of 0. 1711 1712Consequently, it is very simple for userspace to define the amount of memory to 1713consider for each task. Setting a /proc/<pid>/oom_score_adj value of +500, for 1714example, is roughly equivalent to allowing the remainder of tasks sharing the 1715same system, cpuset, mempolicy, or memory controller resources to use at least 171650% more memory. A value of -500, on the other hand, would be roughly 1717equivalent to discounting 50% of the task's allowed memory from being considered 1718as scoring against the task. 1719 1720For backwards compatibility with previous kernels, /proc/<pid>/oom_adj may also 1721be used to tune the badness score. Its acceptable values range from -16 1722(OOM_ADJUST_MIN) to +15 (OOM_ADJUST_MAX) and a special value of -17 1723(OOM_DISABLE) to disable oom killing entirely for that task. Its value is 1724scaled linearly with /proc/<pid>/oom_score_adj. 1725 1726The value of /proc/<pid>/oom_score_adj may be reduced no lower than the last 1727value set by a CAP_SYS_RESOURCE process. To reduce the value any lower 1728requires CAP_SYS_RESOURCE. 1729 1730 17313.2 /proc/<pid>/oom_score - Display current oom-killer score 1732------------------------------------------------------------- 1733 1734This file can be used to check the current score used by the oom-killer for 1735any given <pid>. Use it together with /proc/<pid>/oom_score_adj to tune which 1736process should be killed in an out-of-memory situation. 1737 1738Please note that the exported value includes oom_score_adj so it is 1739effectively in range [0,2000]. 1740 1741 17423.3 /proc/<pid>/io - Display the IO accounting fields 1743------------------------------------------------------- 1744 1745This file contains IO statistics for each running process. 1746 1747Example 1748~~~~~~~ 1749 1750:: 1751 1752 test:/tmp # dd if=/dev/zero of=/tmp/test.dat & 1753 [1] 3828 1754 1755 test:/tmp # cat /proc/3828/io 1756 rchar: 323934931 1757 wchar: 323929600 1758 syscr: 632687 1759 syscw: 632675 1760 read_bytes: 0 1761 write_bytes: 323932160 1762 cancelled_write_bytes: 0 1763 1764 1765Description 1766~~~~~~~~~~~ 1767 1768rchar 1769^^^^^ 1770 1771I/O counter: chars read 1772The number of bytes which this task has caused to be read from storage. This 1773is simply the sum of bytes which this process passed to read() and pread(). 1774It includes things like tty IO and it is unaffected by whether or not actual 1775physical disk IO was required (the read might have been satisfied from 1776pagecache). 1777 1778 1779wchar 1780^^^^^ 1781 1782I/O counter: chars written 1783The number of bytes which this task has caused, or shall cause to be written 1784to disk. Similar caveats apply here as with rchar. 1785 1786 1787syscr 1788^^^^^ 1789 1790I/O counter: read syscalls 1791Attempt to count the number of read I/O operations, i.e. syscalls like read() 1792and pread(). 1793 1794 1795syscw 1796^^^^^ 1797 1798I/O counter: write syscalls 1799Attempt to count the number of write I/O operations, i.e. syscalls like 1800write() and pwrite(). 1801 1802 1803read_bytes 1804^^^^^^^^^^ 1805 1806I/O counter: bytes read 1807Attempt to count the number of bytes which this process really did cause to 1808be fetched from the storage layer. Done at the submit_bio() level, so it is 1809accurate for block-backed filesystems. <please add status regarding NFS and 1810CIFS at a later time> 1811 1812 1813write_bytes 1814^^^^^^^^^^^ 1815 1816I/O counter: bytes written 1817Attempt to count the number of bytes which this process caused to be sent to 1818the storage layer. This is done at page-dirtying time. 1819 1820 1821cancelled_write_bytes 1822^^^^^^^^^^^^^^^^^^^^^ 1823 1824The big inaccuracy here is truncate. If a process writes 1MB to a file and 1825then deletes the file, it will in fact perform no writeout. But it will have 1826been accounted as having caused 1MB of write. 1827In other words: The number of bytes which this process caused to not happen, 1828by truncating pagecache. A task can cause "negative" IO too. If this task 1829truncates some dirty pagecache, some IO which another task has been accounted 1830for (in its write_bytes) will not be happening. We _could_ just subtract that 1831from the truncating task's write_bytes, but there is information loss in doing 1832that. 1833 1834 1835.. Note:: 1836 1837 At its current implementation state, this is a bit racy on 32-bit machines: 1838 if process A reads process B's /proc/pid/io while process B is updating one 1839 of those 64-bit counters, process A could see an intermediate result. 1840 1841 1842More information about this can be found within the taskstats documentation in 1843Documentation/accounting. 1844 18453.4 /proc/<pid>/coredump_filter - Core dump filtering settings 1846--------------------------------------------------------------- 1847When a process is dumped, all anonymous memory is written to a core file as 1848long as the size of the core file isn't limited. But sometimes we don't want 1849to dump some memory segments, for example, huge shared memory or DAX. 1850Conversely, sometimes we want to save file-backed memory segments into a core 1851file, not only the individual files. 1852 1853/proc/<pid>/coredump_filter allows you to customize which memory segments 1854will be dumped when the <pid> process is dumped. coredump_filter is a bitmask 1855of memory types. If a bit of the bitmask is set, memory segments of the 1856corresponding memory type are dumped, otherwise they are not dumped. 1857 1858The following 9 memory types are supported: 1859 1860 - (bit 0) anonymous private memory 1861 - (bit 1) anonymous shared memory 1862 - (bit 2) file-backed private memory 1863 - (bit 3) file-backed shared memory 1864 - (bit 4) ELF header pages in file-backed private memory areas (it is 1865 effective only if the bit 2 is cleared) 1866 - (bit 5) hugetlb private memory 1867 - (bit 6) hugetlb shared memory 1868 - (bit 7) DAX private memory 1869 - (bit 8) DAX shared memory 1870 1871 Note that MMIO pages such as frame buffer are never dumped and vDSO pages 1872 are always dumped regardless of the bitmask status. 1873 1874 Note that bits 0-4 don't affect hugetlb or DAX memory. hugetlb memory is 1875 only affected by bit 5-6, and DAX is only affected by bits 7-8. 1876 1877The default value of coredump_filter is 0x33; this means all anonymous memory 1878segments, ELF header pages and hugetlb private memory are dumped. 1879 1880If you don't want to dump all shared memory segments attached to pid 1234, 1881write 0x31 to the process's proc file:: 1882 1883 $ echo 0x31 > /proc/1234/coredump_filter 1884 1885When a new process is created, the process inherits the bitmask status from its 1886parent. It is useful to set up coredump_filter before the program runs. 1887For example:: 1888 1889 $ echo 0x7 > /proc/self/coredump_filter 1890 $ ./some_program 1891 18923.5 /proc/<pid>/mountinfo - Information about mounts 1893-------------------------------------------------------- 1894 1895This file contains lines of the form:: 1896 1897 36 35 98:0 /mnt1 /mnt2 rw,noatime master:1 - ext3 /dev/root rw,errors=continue 1898 (1)(2)(3) (4) (5) (6) (n…m) (m+1)(m+2) (m+3) (m+4) 1899 1900 (1) mount ID: unique identifier of the mount (may be reused after umount) 1901 (2) parent ID: ID of parent (or of self for the top of the mount tree) 1902 (3) major:minor: value of st_dev for files on filesystem 1903 (4) root: root of the mount within the filesystem 1904 (5) mount point: mount point relative to the process's root 1905 (6) mount options: per mount options 1906 (n…m) optional fields: zero or more fields of the form "tag[:value]" 1907 (m+1) separator: marks the end of the optional fields 1908 (m+2) filesystem type: name of filesystem of the form "type[.subtype]" 1909 (m+3) mount source: filesystem specific information or "none" 1910 (m+4) super options: per super block options 1911 1912Parsers should ignore all unrecognised optional fields. Currently the 1913possible optional fields are: 1914 1915================ ============================================================== 1916shared:X mount is shared in peer group X 1917master:X mount is slave to peer group X 1918propagate_from:X mount is slave and receives propagation from peer group X [#]_ 1919unbindable mount is unbindable 1920================ ============================================================== 1921 1922.. [#] X is the closest dominant peer group under the process's root. If 1923 X is the immediate master of the mount, or if there's no dominant peer 1924 group under the same root, then only the "master:X" field is present 1925 and not the "propagate_from:X" field. 1926 1927For more information on mount propagation see: 1928 1929 Documentation/filesystems/sharedsubtree.rst 1930 1931 19323.6 /proc/<pid>/comm & /proc/<pid>/task/<tid>/comm 1933-------------------------------------------------------- 1934These files provide a method to access a task's comm value. It also allows for 1935a task to set its own or one of its thread siblings comm value. The comm value 1936is limited in size compared to the cmdline value, so writing anything longer 1937then the kernel's TASK_COMM_LEN (currently 16 chars) will result in a truncated 1938comm value. 1939 1940 19413.7 /proc/<pid>/task/<tid>/children - Information about task children 1942------------------------------------------------------------------------- 1943This file provides a fast way to retrieve first level children pids 1944of a task pointed by <pid>/<tid> pair. The format is a space separated 1945stream of pids. 1946 1947Note the "first level" here -- if a child has its own children they will 1948not be listed here; one needs to read /proc/<children-pid>/task/<tid>/children 1949to obtain the descendants. 1950 1951Since this interface is intended to be fast and cheap it doesn't 1952guarantee to provide precise results and some children might be 1953skipped, especially if they've exited right after we printed their 1954pids, so one needs to either stop or freeze processes being inspected 1955if precise results are needed. 1956 1957 19583.8 /proc/<pid>/fdinfo/<fd> - Information about opened file 1959--------------------------------------------------------------- 1960This file provides information associated with an opened file. The regular 1961files have at least four fields -- 'pos', 'flags', 'mnt_id' and 'ino'. 1962The 'pos' represents the current offset of the opened file in decimal 1963form [see lseek(2) for details], 'flags' denotes the octal O_xxx mask the 1964file has been created with [see open(2) for details] and 'mnt_id' represents 1965mount ID of the file system containing the opened file [see 3.5 1966/proc/<pid>/mountinfo for details]. 'ino' represents the inode number of 1967the file. 1968 1969A typical output is:: 1970 1971 pos: 0 1972 flags: 0100002 1973 mnt_id: 19 1974 ino: 63107 1975 1976All locks associated with a file descriptor are shown in its fdinfo too:: 1977 1978 lock: 1: FLOCK ADVISORY WRITE 359 00:13:11691 0 EOF 1979 1980The files such as eventfd, fsnotify, signalfd, epoll among the regular pos/flags 1981pair provide additional information particular to the objects they represent. 1982 1983Eventfd files 1984~~~~~~~~~~~~~ 1985 1986:: 1987 1988 pos: 0 1989 flags: 04002 1990 mnt_id: 9 1991 ino: 63107 1992 eventfd-count: 5a 1993 1994where 'eventfd-count' is hex value of a counter. 1995 1996Signalfd files 1997~~~~~~~~~~~~~~ 1998 1999:: 2000 2001 pos: 0 2002 flags: 04002 2003 mnt_id: 9 2004 ino: 63107 2005 sigmask: 0000000000000200 2006 2007where 'sigmask' is hex value of the signal mask associated 2008with a file. 2009 2010Epoll files 2011~~~~~~~~~~~ 2012 2013:: 2014 2015 pos: 0 2016 flags: 02 2017 mnt_id: 9 2018 ino: 63107 2019 tfd: 5 events: 1d data: ffffffffffffffff pos:0 ino:61af sdev:7 2020 2021where 'tfd' is a target file descriptor number in decimal form, 2022'events' is events mask being watched and the 'data' is data 2023associated with a target [see epoll(7) for more details]. 2024 2025The 'pos' is current offset of the target file in decimal form 2026[see lseek(2)], 'ino' and 'sdev' are inode and device numbers 2027where target file resides, all in hex format. 2028 2029Fsnotify files 2030~~~~~~~~~~~~~~ 2031For inotify files the format is the following:: 2032 2033 pos: 0 2034 flags: 02000000 2035 mnt_id: 9 2036 ino: 63107 2037 inotify wd:3 ino:9e7e sdev:800013 mask:800afce ignored_mask:0 fhandle-bytes:8 fhandle-type:1 f_handle:7e9e0000640d1b6d 2038 2039where 'wd' is a watch descriptor in decimal form, i.e. a target file 2040descriptor number, 'ino' and 'sdev' are inode and device where the 2041target file resides and the 'mask' is the mask of events, all in hex 2042form [see inotify(7) for more details]. 2043 2044If the kernel was built with exportfs support, the path to the target 2045file is encoded as a file handle. The file handle is provided by three 2046fields 'fhandle-bytes', 'fhandle-type' and 'f_handle', all in hex 2047format. 2048 2049If the kernel is built without exportfs support the file handle won't be 2050printed out. 2051 2052If there is no inotify mark attached yet the 'inotify' line will be omitted. 2053 2054For fanotify files the format is:: 2055 2056 pos: 0 2057 flags: 02 2058 mnt_id: 9 2059 ino: 63107 2060 fanotify flags:10 event-flags:0 2061 fanotify mnt_id:12 mflags:40 mask:38 ignored_mask:40000003 2062 fanotify ino:4f969 sdev:800013 mflags:0 mask:3b ignored_mask:40000000 fhandle-bytes:8 fhandle-type:1 f_handle:69f90400c275b5b4 2063 2064where fanotify 'flags' and 'event-flags' are values used in fanotify_init 2065call, 'mnt_id' is the mount point identifier, 'mflags' is the value of 2066flags associated with mark which are tracked separately from events 2067mask. 'ino' and 'sdev' are target inode and device, 'mask' is the events 2068mask and 'ignored_mask' is the mask of events which are to be ignored. 2069All are in hex format. Incorporation of 'mflags', 'mask' and 'ignored_mask' 2070provide information about flags and mask used in fanotify_mark 2071call [see fsnotify manpage for details]. 2072 2073While the first three lines are mandatory and always printed, the rest is 2074optional and may be omitted if no marks created yet. 2075 2076Timerfd files 2077~~~~~~~~~~~~~ 2078 2079:: 2080 2081 pos: 0 2082 flags: 02 2083 mnt_id: 9 2084 ino: 63107 2085 clockid: 0 2086 ticks: 0 2087 settime flags: 01 2088 it_value: (0, 49406829) 2089 it_interval: (1, 0) 2090 2091where 'clockid' is the clock type and 'ticks' is the number of the timer expirations 2092that have occurred [see timerfd_create(2) for details]. 'settime flags' are 2093flags in octal form been used to setup the timer [see timerfd_settime(2) for 2094details]. 'it_value' is remaining time until the timer expiration. 2095'it_interval' is the interval for the timer. Note the timer might be set up 2096with TIMER_ABSTIME option which will be shown in 'settime flags', but 'it_value' 2097still exhibits timer's remaining time. 2098 2099DMA Buffer files 2100~~~~~~~~~~~~~~~~ 2101 2102:: 2103 2104 pos: 0 2105 flags: 04002 2106 mnt_id: 9 2107 ino: 63107 2108 size: 32768 2109 count: 2 2110 exp_name: system-heap 2111 2112where 'size' is the size of the DMA buffer in bytes. 'count' is the file count of 2113the DMA buffer file. 'exp_name' is the name of the DMA buffer exporter. 2114 21153.9 /proc/<pid>/map_files - Information about memory mapped files 2116--------------------------------------------------------------------- 2117This directory contains symbolic links which represent memory mapped files 2118the process is maintaining. Example output:: 2119 2120 | lr-------- 1 root root 64 Jan 27 11:24 333c600000-333c620000 -> /usr/lib64/ld-2.18.so 2121 | lr-------- 1 root root 64 Jan 27 11:24 333c81f000-333c820000 -> /usr/lib64/ld-2.18.so 2122 | lr-------- 1 root root 64 Jan 27 11:24 333c820000-333c821000 -> /usr/lib64/ld-2.18.so 2123 | ... 2124 | lr-------- 1 root root 64 Jan 27 11:24 35d0421000-35d0422000 -> /usr/lib64/libselinux.so.1 2125 | lr-------- 1 root root 64 Jan 27 11:24 400000-41a000 -> /usr/bin/ls 2126 2127The name of a link represents the virtual memory bounds of a mapping, i.e. 2128vm_area_struct::vm_start-vm_area_struct::vm_end. 2129 2130The main purpose of the map_files is to retrieve a set of memory mapped 2131files in a fast way instead of parsing /proc/<pid>/maps or 2132/proc/<pid>/smaps, both of which contain many more records. At the same 2133time one can open(2) mappings from the listings of two processes and 2134comparing their inode numbers to figure out which anonymous memory areas 2135are actually shared. 2136 21373.10 /proc/<pid>/timerslack_ns - Task timerslack value 2138--------------------------------------------------------- 2139This file provides the value of the task's timerslack value in nanoseconds. 2140This value specifies an amount of time that normal timers may be deferred 2141in order to coalesce timers and avoid unnecessary wakeups. 2142 2143This allows a task's interactivity vs power consumption tradeoff to be 2144adjusted. 2145 2146Writing 0 to the file will set the task's timerslack to the default value. 2147 2148Valid values are from 0 - ULLONG_MAX 2149 2150An application setting the value must have PTRACE_MODE_ATTACH_FSCREDS level 2151permissions on the task specified to change its timerslack_ns value. 2152 21533.11 /proc/<pid>/patch_state - Livepatch patch operation state 2154----------------------------------------------------------------- 2155When CONFIG_LIVEPATCH is enabled, this file displays the value of the 2156patch state for the task. 2157 2158A value of '-1' indicates that no patch is in transition. 2159 2160A value of '0' indicates that a patch is in transition and the task is 2161unpatched. If the patch is being enabled, then the task hasn't been 2162patched yet. If the patch is being disabled, then the task has already 2163been unpatched. 2164 2165A value of '1' indicates that a patch is in transition and the task is 2166patched. If the patch is being enabled, then the task has already been 2167patched. If the patch is being disabled, then the task hasn't been 2168unpatched yet. 2169 21703.12 /proc/<pid>/arch_status - task architecture specific status 2171------------------------------------------------------------------- 2172When CONFIG_PROC_PID_ARCH_STATUS is enabled, this file displays the 2173architecture specific status of the task. 2174 2175Example 2176~~~~~~~ 2177 2178:: 2179 2180 $ cat /proc/6753/arch_status 2181 AVX512_elapsed_ms: 8 2182 2183Description 2184~~~~~~~~~~~ 2185 2186x86 specific entries 2187~~~~~~~~~~~~~~~~~~~~~ 2188 2189AVX512_elapsed_ms 2190^^^^^^^^^^^^^^^^^^ 2191 2192 If AVX512 is supported on the machine, this entry shows the milliseconds 2193 elapsed since the last time AVX512 usage was recorded. The recording 2194 happens on a best effort basis when a task is scheduled out. This means 2195 that the value depends on two factors: 2196 2197 1) The time which the task spent on the CPU without being scheduled 2198 out. With CPU isolation and a single runnable task this can take 2199 several seconds. 2200 2201 2) The time since the task was scheduled out last. Depending on the 2202 reason for being scheduled out (time slice exhausted, syscall ...) 2203 this can be arbitrary long time. 2204 2205 As a consequence the value cannot be considered precise and authoritative 2206 information. The application which uses this information has to be aware 2207 of the overall scenario on the system in order to determine whether a 2208 task is a real AVX512 user or not. Precise information can be obtained 2209 with performance counters. 2210 2211 A special value of '-1' indicates that no AVX512 usage was recorded, thus 2212 the task is unlikely an AVX512 user, but depends on the workload and the 2213 scheduling scenario, it also could be a false negative mentioned above. 2214 2215Chapter 4: Configuring procfs 2216============================= 2217 22184.1 Mount options 2219--------------------- 2220 2221The following mount options are supported: 2222 2223 ========= ======================================================== 2224 hidepid= Set /proc/<pid>/ access mode. 2225 gid= Set the group authorized to learn processes information. 2226 subset= Show only the specified subset of procfs. 2227 ========= ======================================================== 2228 2229hidepid=off or hidepid=0 means classic mode - everybody may access all 2230/proc/<pid>/ directories (default). 2231 2232hidepid=noaccess or hidepid=1 means users may not access any /proc/<pid>/ 2233directories but their own. Sensitive files like cmdline, sched*, status are now 2234protected against other users. This makes it impossible to learn whether any 2235user runs specific program (given the program doesn't reveal itself by its 2236behaviour). As an additional bonus, as /proc/<pid>/cmdline is unaccessible for 2237other users, poorly written programs passing sensitive information via program 2238arguments are now protected against local eavesdroppers. 2239 2240hidepid=invisible or hidepid=2 means hidepid=1 plus all /proc/<pid>/ will be 2241fully invisible to other users. It doesn't mean that it hides a fact whether a 2242process with a specific pid value exists (it can be learned by other means, e.g. 2243by "kill -0 $PID"), but it hides process' uid and gid, which may be learned by 2244stat()'ing /proc/<pid>/ otherwise. It greatly complicates an intruder's task of 2245gathering information about running processes, whether some daemon runs with 2246elevated privileges, whether other user runs some sensitive program, whether 2247other users run any program at all, etc. 2248 2249hidepid=ptraceable or hidepid=4 means that procfs should only contain 2250/proc/<pid>/ directories that the caller can ptrace. 2251 2252gid= defines a group authorized to learn processes information otherwise 2253prohibited by hidepid=. If you use some daemon like identd which needs to learn 2254information about processes information, just add identd to this group. 2255 2256subset=pid hides all top level files and directories in the procfs that 2257are not related to tasks. 2258 2259Chapter 5: Filesystem behavior 2260============================== 2261 2262Originally, before the advent of pid namepsace, procfs was a global file 2263system. It means that there was only one procfs instance in the system. 2264 2265When pid namespace was added, a separate procfs instance was mounted in 2266each pid namespace. So, procfs mount options are global among all 2267mountpoints within the same namespace:: 2268 2269 # grep ^proc /proc/mounts 2270 proc /proc proc rw,relatime,hidepid=2 0 0 2271 2272 # strace -e mount mount -o hidepid=1 -t proc proc /tmp/proc 2273 mount("proc", "/tmp/proc", "proc", 0, "hidepid=1") = 0 2274 +++ exited with 0 +++ 2275 2276 # grep ^proc /proc/mounts 2277 proc /proc proc rw,relatime,hidepid=2 0 0 2278 proc /tmp/proc proc rw,relatime,hidepid=2 0 0 2279 2280and only after remounting procfs mount options will change at all 2281mountpoints:: 2282 2283 # mount -o remount,hidepid=1 -t proc proc /tmp/proc 2284 2285 # grep ^proc /proc/mounts 2286 proc /proc proc rw,relatime,hidepid=1 0 0 2287 proc /tmp/proc proc rw,relatime,hidepid=1 0 0 2288 2289This behavior is different from the behavior of other filesystems. 2290 2291The new procfs behavior is more like other filesystems. Each procfs mount 2292creates a new procfs instance. Mount options affect own procfs instance. 2293It means that it became possible to have several procfs instances 2294displaying tasks with different filtering options in one pid namespace:: 2295 2296 # mount -o hidepid=invisible -t proc proc /proc 2297 # mount -o hidepid=noaccess -t proc proc /tmp/proc 2298 # grep ^proc /proc/mounts 2299 proc /proc proc rw,relatime,hidepid=invisible 0 0 2300 proc /tmp/proc proc rw,relatime,hidepid=noaccess 0 0 2301