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 Zswap: 1904 kB 968 Zswapped: 7792 kB 969 Dirty: 12 kB 970 Writeback: 0 kB 971 AnonPages: 4654780 kB 972 Mapped: 266244 kB 973 Shmem: 9976 kB 974 KReclaimable: 517708 kB 975 Slab: 660044 kB 976 SReclaimable: 517708 kB 977 SUnreclaim: 142336 kB 978 KernelStack: 11168 kB 979 PageTables: 20540 kB 980 NFS_Unstable: 0 kB 981 Bounce: 0 kB 982 WritebackTmp: 0 kB 983 CommitLimit: 16429408 kB 984 Committed_AS: 7715148 kB 985 VmallocTotal: 34359738367 kB 986 VmallocUsed: 40444 kB 987 VmallocChunk: 0 kB 988 Percpu: 29312 kB 989 HardwareCorrupted: 0 kB 990 AnonHugePages: 4149248 kB 991 ShmemHugePages: 0 kB 992 ShmemPmdMapped: 0 kB 993 FileHugePages: 0 kB 994 FilePmdMapped: 0 kB 995 CmaTotal: 0 kB 996 CmaFree: 0 kB 997 HugePages_Total: 0 998 HugePages_Free: 0 999 HugePages_Rsvd: 0 1000 HugePages_Surp: 0 1001 Hugepagesize: 2048 kB 1002 Hugetlb: 0 kB 1003 DirectMap4k: 401152 kB 1004 DirectMap2M: 10008576 kB 1005 DirectMap1G: 24117248 kB 1006 1007MemTotal 1008 Total usable RAM (i.e. physical RAM minus a few reserved 1009 bits and the kernel binary code) 1010MemFree 1011 Total free RAM. On highmem systems, the sum of LowFree+HighFree 1012MemAvailable 1013 An estimate of how much memory is available for starting new 1014 applications, without swapping. Calculated from MemFree, 1015 SReclaimable, the size of the file LRU lists, and the low 1016 watermarks in each zone. 1017 The estimate takes into account that the system needs some 1018 page cache to function well, and that not all reclaimable 1019 slab will be reclaimable, due to items being in use. The 1020 impact of those factors will vary from system to system. 1021Buffers 1022 Relatively temporary storage for raw disk blocks 1023 shouldn't get tremendously large (20MB or so) 1024Cached 1025 In-memory cache for files read from the disk (the 1026 pagecache) as well as tmpfs & shmem. 1027 Doesn't include SwapCached. 1028SwapCached 1029 Memory that once was swapped out, is swapped back in but 1030 still also is in the swapfile (if memory is needed it 1031 doesn't need to be swapped out AGAIN because it is already 1032 in the swapfile. This saves I/O) 1033Active 1034 Memory that has been used more recently and usually not 1035 reclaimed unless absolutely necessary. 1036Inactive 1037 Memory which has been less recently used. It is more 1038 eligible to be reclaimed for other purposes 1039Unevictable 1040 Memory allocated for userspace which cannot be reclaimed, such 1041 as mlocked pages, ramfs backing pages, secret memfd pages etc. 1042Mlocked 1043 Memory locked with mlock(). 1044HighTotal, HighFree 1045 Highmem is all memory above ~860MB of physical memory. 1046 Highmem areas are for use by userspace programs, or 1047 for the pagecache. The kernel must use tricks to access 1048 this memory, making it slower to access than lowmem. 1049LowTotal, LowFree 1050 Lowmem is memory which can be used for everything that 1051 highmem can be used for, but it is also available for the 1052 kernel's use for its own data structures. Among many 1053 other things, it is where everything from the Slab is 1054 allocated. Bad things happen when you're out of lowmem. 1055SwapTotal 1056 total amount of swap space available 1057SwapFree 1058 Memory which has been evicted from RAM, and is temporarily 1059 on the disk 1060Zswap 1061 Memory consumed by the zswap backend (compressed size) 1062Zswapped 1063 Amount of anonymous memory stored in zswap (original size) 1064Dirty 1065 Memory which is waiting to get written back to the disk 1066Writeback 1067 Memory which is actively being written back to the disk 1068AnonPages 1069 Non-file backed pages mapped into userspace page tables 1070Mapped 1071 files which have been mmaped, such as libraries 1072Shmem 1073 Total memory used by shared memory (shmem) and tmpfs 1074KReclaimable 1075 Kernel allocations that the kernel will attempt to reclaim 1076 under memory pressure. Includes SReclaimable (below), and other 1077 direct allocations with a shrinker. 1078Slab 1079 in-kernel data structures cache 1080SReclaimable 1081 Part of Slab, that might be reclaimed, such as caches 1082SUnreclaim 1083 Part of Slab, that cannot be reclaimed on memory pressure 1084KernelStack 1085 Memory consumed by the kernel stacks of all tasks 1086PageTables 1087 Memory consumed by userspace page tables 1088NFS_Unstable 1089 Always zero. Previous counted pages which had been written to 1090 the server, but has not been committed to stable storage. 1091Bounce 1092 Memory used for block device "bounce buffers" 1093WritebackTmp 1094 Memory used by FUSE for temporary writeback buffers 1095CommitLimit 1096 Based on the overcommit ratio ('vm.overcommit_ratio'), 1097 this is the total amount of memory currently available to 1098 be allocated on the system. This limit is only adhered to 1099 if strict overcommit accounting is enabled (mode 2 in 1100 'vm.overcommit_memory'). 1101 1102 The CommitLimit is calculated with the following formula:: 1103 1104 CommitLimit = ([total RAM pages] - [total huge TLB pages]) * 1105 overcommit_ratio / 100 + [total swap pages] 1106 1107 For example, on a system with 1G of physical RAM and 7G 1108 of swap with a `vm.overcommit_ratio` of 30 it would 1109 yield a CommitLimit of 7.3G. 1110 1111 For more details, see the memory overcommit documentation 1112 in vm/overcommit-accounting. 1113Committed_AS 1114 The amount of memory presently allocated on the system. 1115 The committed memory is a sum of all of the memory which 1116 has been allocated by processes, even if it has not been 1117 "used" by them as of yet. A process which malloc()'s 1G 1118 of memory, but only touches 300M of it will show up as 1119 using 1G. This 1G is memory which has been "committed" to 1120 by the VM and can be used at any time by the allocating 1121 application. With strict overcommit enabled on the system 1122 (mode 2 in 'vm.overcommit_memory'), allocations which would 1123 exceed the CommitLimit (detailed above) will not be permitted. 1124 This is useful if one needs to guarantee that processes will 1125 not fail due to lack of memory once that memory has been 1126 successfully allocated. 1127VmallocTotal 1128 total size of vmalloc virtual address space 1129VmallocUsed 1130 amount of vmalloc area which is used 1131VmallocChunk 1132 largest contiguous block of vmalloc area which is free 1133Percpu 1134 Memory allocated to the percpu allocator used to back percpu 1135 allocations. This stat excludes the cost of metadata. 1136HardwareCorrupted 1137 The amount of RAM/memory in KB, the kernel identifies as 1138 corrupted. 1139AnonHugePages 1140 Non-file backed huge pages mapped into userspace page tables 1141ShmemHugePages 1142 Memory used by shared memory (shmem) and tmpfs allocated 1143 with huge pages 1144ShmemPmdMapped 1145 Shared memory mapped into userspace with huge pages 1146FileHugePages 1147 Memory used for filesystem data (page cache) allocated 1148 with huge pages 1149FilePmdMapped 1150 Page cache mapped into userspace with huge pages 1151CmaTotal 1152 Memory reserved for the Contiguous Memory Allocator (CMA) 1153CmaFree 1154 Free remaining memory in the CMA reserves 1155HugePages_Total, HugePages_Free, HugePages_Rsvd, HugePages_Surp, Hugepagesize, Hugetlb 1156 See Documentation/admin-guide/mm/hugetlbpage.rst. 1157DirectMap4k, DirectMap2M, DirectMap1G 1158 Breakdown of page table sizes used in the kernel's 1159 identity mapping of RAM 1160 1161vmallocinfo 1162~~~~~~~~~~~ 1163 1164Provides information about vmalloced/vmaped areas. One line per area, 1165containing the virtual address range of the area, size in bytes, 1166caller information of the creator, and optional information depending 1167on the kind of area: 1168 1169 ========== =================================================== 1170 pages=nr number of pages 1171 phys=addr if a physical address was specified 1172 ioremap I/O mapping (ioremap() and friends) 1173 vmalloc vmalloc() area 1174 vmap vmap()ed pages 1175 user VM_USERMAP area 1176 vpages buffer for pages pointers was vmalloced (huge area) 1177 N<node>=nr (Only on NUMA kernels) 1178 Number of pages allocated on memory node <node> 1179 ========== =================================================== 1180 1181:: 1182 1183 > cat /proc/vmallocinfo 1184 0xffffc20000000000-0xffffc20000201000 2101248 alloc_large_system_hash+0x204 ... 1185 /0x2c0 pages=512 vmalloc N0=128 N1=128 N2=128 N3=128 1186 0xffffc20000201000-0xffffc20000302000 1052672 alloc_large_system_hash+0x204 ... 1187 /0x2c0 pages=256 vmalloc N0=64 N1=64 N2=64 N3=64 1188 0xffffc20000302000-0xffffc20000304000 8192 acpi_tb_verify_table+0x21/0x4f... 1189 phys=7fee8000 ioremap 1190 0xffffc20000304000-0xffffc20000307000 12288 acpi_tb_verify_table+0x21/0x4f... 1191 phys=7fee7000 ioremap 1192 0xffffc2000031d000-0xffffc2000031f000 8192 init_vdso_vars+0x112/0x210 1193 0xffffc2000031f000-0xffffc2000032b000 49152 cramfs_uncompress_init+0x2e ... 1194 /0x80 pages=11 vmalloc N0=3 N1=3 N2=2 N3=3 1195 0xffffc2000033a000-0xffffc2000033d000 12288 sys_swapon+0x640/0xac0 ... 1196 pages=2 vmalloc N1=2 1197 0xffffc20000347000-0xffffc2000034c000 20480 xt_alloc_table_info+0xfe ... 1198 /0x130 [x_tables] pages=4 vmalloc N0=4 1199 0xffffffffa0000000-0xffffffffa000f000 61440 sys_init_module+0xc27/0x1d00 ... 1200 pages=14 vmalloc N2=14 1201 0xffffffffa000f000-0xffffffffa0014000 20480 sys_init_module+0xc27/0x1d00 ... 1202 pages=4 vmalloc N1=4 1203 0xffffffffa0014000-0xffffffffa0017000 12288 sys_init_module+0xc27/0x1d00 ... 1204 pages=2 vmalloc N1=2 1205 0xffffffffa0017000-0xffffffffa0022000 45056 sys_init_module+0xc27/0x1d00 ... 1206 pages=10 vmalloc N0=10 1207 1208 1209softirqs 1210~~~~~~~~ 1211 1212Provides counts of softirq handlers serviced since boot time, for each CPU. 1213 1214:: 1215 1216 > cat /proc/softirqs 1217 CPU0 CPU1 CPU2 CPU3 1218 HI: 0 0 0 0 1219 TIMER: 27166 27120 27097 27034 1220 NET_TX: 0 0 0 17 1221 NET_RX: 42 0 0 39 1222 BLOCK: 0 0 107 1121 1223 TASKLET: 0 0 0 290 1224 SCHED: 27035 26983 26971 26746 1225 HRTIMER: 0 0 0 0 1226 RCU: 1678 1769 2178 2250 1227 12281.3 Networking info in /proc/net 1229-------------------------------- 1230 1231The subdirectory /proc/net follows the usual pattern. Table 1-8 shows the 1232additional values you get for IP version 6 if you configure the kernel to 1233support this. Table 1-9 lists the files and their meaning. 1234 1235 1236.. table:: Table 1-8: IPv6 info in /proc/net 1237 1238 ========== ===================================================== 1239 File Content 1240 ========== ===================================================== 1241 udp6 UDP sockets (IPv6) 1242 tcp6 TCP sockets (IPv6) 1243 raw6 Raw device statistics (IPv6) 1244 igmp6 IP multicast addresses, which this host joined (IPv6) 1245 if_inet6 List of IPv6 interface addresses 1246 ipv6_route Kernel routing table for IPv6 1247 rt6_stats Global IPv6 routing tables statistics 1248 sockstat6 Socket statistics (IPv6) 1249 snmp6 Snmp data (IPv6) 1250 ========== ===================================================== 1251 1252.. table:: Table 1-9: Network info in /proc/net 1253 1254 ============= ================================================================ 1255 File Content 1256 ============= ================================================================ 1257 arp Kernel ARP table 1258 dev network devices with statistics 1259 dev_mcast the Layer2 multicast groups a device is listening too 1260 (interface index, label, number of references, number of bound 1261 addresses). 1262 dev_stat network device status 1263 ip_fwchains Firewall chain linkage 1264 ip_fwnames Firewall chain names 1265 ip_masq Directory containing the masquerading tables 1266 ip_masquerade Major masquerading table 1267 netstat Network statistics 1268 raw raw device statistics 1269 route Kernel routing table 1270 rpc Directory containing rpc info 1271 rt_cache Routing cache 1272 snmp SNMP data 1273 sockstat Socket statistics 1274 tcp TCP sockets 1275 udp UDP sockets 1276 unix UNIX domain sockets 1277 wireless Wireless interface data (Wavelan etc) 1278 igmp IP multicast addresses, which this host joined 1279 psched Global packet scheduler parameters. 1280 netlink List of PF_NETLINK sockets 1281 ip_mr_vifs List of multicast virtual interfaces 1282 ip_mr_cache List of multicast routing cache 1283 ============= ================================================================ 1284 1285You can use this information to see which network devices are available in 1286your system and how much traffic was routed over those devices:: 1287 1288 > cat /proc/net/dev 1289 Inter-|Receive |[... 1290 face |bytes packets errs drop fifo frame compressed multicast|[... 1291 lo: 908188 5596 0 0 0 0 0 0 [... 1292 ppp0:15475140 20721 410 0 0 410 0 0 [... 1293 eth0: 614530 7085 0 0 0 0 0 1 [... 1294 1295 ...] Transmit 1296 ...] bytes packets errs drop fifo colls carrier compressed 1297 ...] 908188 5596 0 0 0 0 0 0 1298 ...] 1375103 17405 0 0 0 0 0 0 1299 ...] 1703981 5535 0 0 0 3 0 0 1300 1301In addition, each Channel Bond interface has its own directory. For 1302example, the bond0 device will have a directory called /proc/net/bond0/. 1303It will contain information that is specific to that bond, such as the 1304current slaves of the bond, the link status of the slaves, and how 1305many times the slaves link has failed. 1306 13071.4 SCSI info 1308------------- 1309 1310If you have a SCSI host adapter in your system, you'll find a subdirectory 1311named after the driver for this adapter in /proc/scsi. You'll also see a list 1312of all recognized SCSI devices in /proc/scsi:: 1313 1314 >cat /proc/scsi/scsi 1315 Attached devices: 1316 Host: scsi0 Channel: 00 Id: 00 Lun: 00 1317 Vendor: IBM Model: DGHS09U Rev: 03E0 1318 Type: Direct-Access ANSI SCSI revision: 03 1319 Host: scsi0 Channel: 00 Id: 06 Lun: 00 1320 Vendor: PIONEER Model: CD-ROM DR-U06S Rev: 1.04 1321 Type: CD-ROM ANSI SCSI revision: 02 1322 1323 1324The directory named after the driver has one file for each adapter found in 1325the system. These files contain information about the controller, including 1326the used IRQ and the IO address range. The amount of information shown is 1327dependent on the adapter you use. The example shows the output for an Adaptec 1328AHA-2940 SCSI adapter:: 1329 1330 > cat /proc/scsi/aic7xxx/0 1331 1332 Adaptec AIC7xxx driver version: 5.1.19/3.2.4 1333 Compile Options: 1334 TCQ Enabled By Default : Disabled 1335 AIC7XXX_PROC_STATS : Disabled 1336 AIC7XXX_RESET_DELAY : 5 1337 Adapter Configuration: 1338 SCSI Adapter: Adaptec AHA-294X Ultra SCSI host adapter 1339 Ultra Wide Controller 1340 PCI MMAPed I/O Base: 0xeb001000 1341 Adapter SEEPROM Config: SEEPROM found and used. 1342 Adaptec SCSI BIOS: Enabled 1343 IRQ: 10 1344 SCBs: Active 0, Max Active 2, 1345 Allocated 15, HW 16, Page 255 1346 Interrupts: 160328 1347 BIOS Control Word: 0x18b6 1348 Adapter Control Word: 0x005b 1349 Extended Translation: Enabled 1350 Disconnect Enable Flags: 0xffff 1351 Ultra Enable Flags: 0x0001 1352 Tag Queue Enable Flags: 0x0000 1353 Ordered Queue Tag Flags: 0x0000 1354 Default Tag Queue Depth: 8 1355 Tagged Queue By Device array for aic7xxx host instance 0: 1356 {255,255,255,255,255,255,255,255,255,255,255,255,255,255,255,255} 1357 Actual queue depth per device for aic7xxx host instance 0: 1358 {1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1} 1359 Statistics: 1360 (scsi0:0:0:0) 1361 Device using Wide/Sync transfers at 40.0 MByte/sec, offset 8 1362 Transinfo settings: current(12/8/1/0), goal(12/8/1/0), user(12/15/1/0) 1363 Total transfers 160151 (74577 reads and 85574 writes) 1364 (scsi0:0:6:0) 1365 Device using Narrow/Sync transfers at 5.0 MByte/sec, offset 15 1366 Transinfo settings: current(50/15/0/0), goal(50/15/0/0), user(50/15/0/0) 1367 Total transfers 0 (0 reads and 0 writes) 1368 1369 13701.5 Parallel port info in /proc/parport 1371--------------------------------------- 1372 1373The directory /proc/parport contains information about the parallel ports of 1374your system. It has one subdirectory for each port, named after the port 1375number (0,1,2,...). 1376 1377These directories contain the four files shown in Table 1-10. 1378 1379 1380.. table:: Table 1-10: Files in /proc/parport 1381 1382 ========= ==================================================================== 1383 File Content 1384 ========= ==================================================================== 1385 autoprobe Any IEEE-1284 device ID information that has been acquired. 1386 devices list of the device drivers using that port. A + will appear by the 1387 name of the device currently using the port (it might not appear 1388 against any). 1389 hardware Parallel port's base address, IRQ line and DMA channel. 1390 irq IRQ that parport is using for that port. This is in a separate 1391 file to allow you to alter it by writing a new value in (IRQ 1392 number or none). 1393 ========= ==================================================================== 1394 13951.6 TTY info in /proc/tty 1396------------------------- 1397 1398Information about the available and actually used tty's can be found in the 1399directory /proc/tty. You'll find entries for drivers and line disciplines in 1400this directory, as shown in Table 1-11. 1401 1402 1403.. table:: Table 1-11: Files in /proc/tty 1404 1405 ============= ============================================== 1406 File Content 1407 ============= ============================================== 1408 drivers list of drivers and their usage 1409 ldiscs registered line disciplines 1410 driver/serial usage statistic and status of single tty lines 1411 ============= ============================================== 1412 1413To see which tty's are currently in use, you can simply look into the file 1414/proc/tty/drivers:: 1415 1416 > cat /proc/tty/drivers 1417 pty_slave /dev/pts 136 0-255 pty:slave 1418 pty_master /dev/ptm 128 0-255 pty:master 1419 pty_slave /dev/ttyp 3 0-255 pty:slave 1420 pty_master /dev/pty 2 0-255 pty:master 1421 serial /dev/cua 5 64-67 serial:callout 1422 serial /dev/ttyS 4 64-67 serial 1423 /dev/tty0 /dev/tty0 4 0 system:vtmaster 1424 /dev/ptmx /dev/ptmx 5 2 system 1425 /dev/console /dev/console 5 1 system:console 1426 /dev/tty /dev/tty 5 0 system:/dev/tty 1427 unknown /dev/tty 4 1-63 console 1428 1429 14301.7 Miscellaneous kernel statistics in /proc/stat 1431------------------------------------------------- 1432 1433Various pieces of information about kernel activity are available in the 1434/proc/stat file. All of the numbers reported in this file are aggregates 1435since the system first booted. For a quick look, simply cat the file:: 1436 1437 > cat /proc/stat 1438 cpu 2255 34 2290 22625563 6290 127 456 0 0 0 1439 cpu0 1132 34 1441 11311718 3675 127 438 0 0 0 1440 cpu1 1123 0 849 11313845 2614 0 18 0 0 0 1441 intr 114930548 113199788 3 0 5 263 0 4 [... lots more numbers ...] 1442 ctxt 1990473 1443 btime 1062191376 1444 processes 2915 1445 procs_running 1 1446 procs_blocked 0 1447 softirq 183433 0 21755 12 39 1137 231 21459 2263 1448 1449The very first "cpu" line aggregates the numbers in all of the other "cpuN" 1450lines. These numbers identify the amount of time the CPU has spent performing 1451different kinds of work. Time units are in USER_HZ (typically hundredths of a 1452second). The meanings of the columns are as follows, from left to right: 1453 1454- user: normal processes executing in user mode 1455- nice: niced processes executing in user mode 1456- system: processes executing in kernel mode 1457- idle: twiddling thumbs 1458- iowait: In a word, iowait stands for waiting for I/O to complete. But there 1459 are several problems: 1460 1461 1. CPU will not wait for I/O to complete, iowait is the time that a task is 1462 waiting for I/O to complete. When CPU goes into idle state for 1463 outstanding task I/O, another task will be scheduled on this CPU. 1464 2. In a multi-core CPU, the task waiting for I/O to complete is not running 1465 on any CPU, so the iowait of each CPU is difficult to calculate. 1466 3. The value of iowait field in /proc/stat will decrease in certain 1467 conditions. 1468 1469 So, the iowait is not reliable by reading from /proc/stat. 1470- irq: servicing interrupts 1471- softirq: servicing softirqs 1472- steal: involuntary wait 1473- guest: running a normal guest 1474- guest_nice: running a niced guest 1475 1476The "intr" line gives counts of interrupts serviced since boot time, for each 1477of the possible system interrupts. The first column is the total of all 1478interrupts serviced including unnumbered architecture specific interrupts; 1479each subsequent column is the total for that particular numbered interrupt. 1480Unnumbered interrupts are not shown, only summed into the total. 1481 1482The "ctxt" line gives the total number of context switches across all CPUs. 1483 1484The "btime" line gives the time at which the system booted, in seconds since 1485the Unix epoch. 1486 1487The "processes" line gives the number of processes and threads created, which 1488includes (but is not limited to) those created by calls to the fork() and 1489clone() system calls. 1490 1491The "procs_running" line gives the total number of threads that are 1492running or ready to run (i.e., the total number of runnable threads). 1493 1494The "procs_blocked" line gives the number of processes currently blocked, 1495waiting for I/O to complete. 1496 1497The "softirq" line gives counts of softirqs serviced since boot time, for each 1498of the possible system softirqs. The first column is the total of all 1499softirqs serviced; each subsequent column is the total for that particular 1500softirq. 1501 1502 15031.8 Ext4 file system parameters 1504------------------------------- 1505 1506Information about mounted ext4 file systems can be found in 1507/proc/fs/ext4. Each mounted filesystem will have a directory in 1508/proc/fs/ext4 based on its device name (i.e., /proc/fs/ext4/hdc or 1509/proc/fs/ext4/dm-0). The files in each per-device directory are shown 1510in Table 1-12, below. 1511 1512.. table:: Table 1-12: Files in /proc/fs/ext4/<devname> 1513 1514 ============== ========================================================== 1515 File Content 1516 mb_groups details of multiblock allocator buddy cache of free blocks 1517 ============== ========================================================== 1518 15191.9 /proc/consoles 1520------------------- 1521Shows registered system console lines. 1522 1523To see which character device lines are currently used for the system console 1524/dev/console, you may simply look into the file /proc/consoles:: 1525 1526 > cat /proc/consoles 1527 tty0 -WU (ECp) 4:7 1528 ttyS0 -W- (Ep) 4:64 1529 1530The columns are: 1531 1532+--------------------+-------------------------------------------------------+ 1533| device | name of the device | 1534+====================+=======================================================+ 1535| operations | * R = can do read operations | 1536| | * W = can do write operations | 1537| | * U = can do unblank | 1538+--------------------+-------------------------------------------------------+ 1539| flags | * E = it is enabled | 1540| | * C = it is preferred console | 1541| | * B = it is primary boot console | 1542| | * p = it is used for printk buffer | 1543| | * b = it is not a TTY but a Braille device | 1544| | * a = it is safe to use when cpu is offline | 1545+--------------------+-------------------------------------------------------+ 1546| major:minor | major and minor number of the device separated by a | 1547| | colon | 1548+--------------------+-------------------------------------------------------+ 1549 1550Summary 1551------- 1552 1553The /proc file system serves information about the running system. It not only 1554allows access to process data but also allows you to request the kernel status 1555by reading files in the hierarchy. 1556 1557The directory structure of /proc reflects the types of information and makes 1558it easy, if not obvious, where to look for specific data. 1559 1560Chapter 2: Modifying System Parameters 1561====================================== 1562 1563In This Chapter 1564--------------- 1565 1566* Modifying kernel parameters by writing into files found in /proc/sys 1567* Exploring the files which modify certain parameters 1568* Review of the /proc/sys file tree 1569 1570------------------------------------------------------------------------------ 1571 1572A very interesting part of /proc is the directory /proc/sys. This is not only 1573a source of information, it also allows you to change parameters within the 1574kernel. Be very careful when attempting this. You can optimize your system, 1575but you can also cause it to crash. Never alter kernel parameters on a 1576production system. Set up a development machine and test to make sure that 1577everything works the way you want it to. You may have no alternative but to 1578reboot the machine once an error has been made. 1579 1580To change a value, simply echo the new value into the file. 1581You need to be root to do this. You can create your own boot script 1582to perform this every time your system boots. 1583 1584The files in /proc/sys can be used to fine tune and monitor miscellaneous and 1585general things in the operation of the Linux kernel. Since some of the files 1586can inadvertently disrupt your system, it is advisable to read both 1587documentation and source before actually making adjustments. In any case, be 1588very careful when writing to any of these files. The entries in /proc may 1589change slightly between the 2.1.* and the 2.2 kernel, so if there is any doubt 1590review the kernel documentation in the directory /usr/src/linux/Documentation. 1591This chapter is heavily based on the documentation included in the pre 2.2 1592kernels, and became part of it in version 2.2.1 of the Linux kernel. 1593 1594Please see: Documentation/admin-guide/sysctl/ directory for descriptions of these 1595entries. 1596 1597Summary 1598------- 1599 1600Certain aspects of kernel behavior can be modified at runtime, without the 1601need to recompile the kernel, or even to reboot the system. The files in the 1602/proc/sys tree can not only be read, but also modified. You can use the echo 1603command to write value into these files, thereby changing the default settings 1604of the kernel. 1605 1606 1607Chapter 3: Per-process Parameters 1608================================= 1609 16103.1 /proc/<pid>/oom_adj & /proc/<pid>/oom_score_adj- Adjust the oom-killer score 1611-------------------------------------------------------------------------------- 1612 1613These files can be used to adjust the badness heuristic used to select which 1614process gets killed in out of memory (oom) conditions. 1615 1616The badness heuristic assigns a value to each candidate task ranging from 0 1617(never kill) to 1000 (always kill) to determine which process is targeted. The 1618units are roughly a proportion along that range of allowed memory the process 1619may allocate from based on an estimation of its current memory and swap use. 1620For example, if a task is using all allowed memory, its badness score will be 16211000. If it is using half of its allowed memory, its score will be 500. 1622 1623The amount of "allowed" memory depends on the context in which the oom killer 1624was called. If it is due to the memory assigned to the allocating task's cpuset 1625being exhausted, the allowed memory represents the set of mems assigned to that 1626cpuset. If it is due to a mempolicy's node(s) being exhausted, the allowed 1627memory represents the set of mempolicy nodes. If it is due to a memory 1628limit (or swap limit) being reached, the allowed memory is that configured 1629limit. Finally, if it is due to the entire system being out of memory, the 1630allowed memory represents all allocatable resources. 1631 1632The value of /proc/<pid>/oom_score_adj is added to the badness score before it 1633is used to determine which task to kill. Acceptable values range from -1000 1634(OOM_SCORE_ADJ_MIN) to +1000 (OOM_SCORE_ADJ_MAX). This allows userspace to 1635polarize the preference for oom killing either by always preferring a certain 1636task or completely disabling it. The lowest possible value, -1000, is 1637equivalent to disabling oom killing entirely for that task since it will always 1638report a badness score of 0. 1639 1640Consequently, it is very simple for userspace to define the amount of memory to 1641consider for each task. Setting a /proc/<pid>/oom_score_adj value of +500, for 1642example, is roughly equivalent to allowing the remainder of tasks sharing the 1643same system, cpuset, mempolicy, or memory controller resources to use at least 164450% more memory. A value of -500, on the other hand, would be roughly 1645equivalent to discounting 50% of the task's allowed memory from being considered 1646as scoring against the task. 1647 1648For backwards compatibility with previous kernels, /proc/<pid>/oom_adj may also 1649be used to tune the badness score. Its acceptable values range from -16 1650(OOM_ADJUST_MIN) to +15 (OOM_ADJUST_MAX) and a special value of -17 1651(OOM_DISABLE) to disable oom killing entirely for that task. Its value is 1652scaled linearly with /proc/<pid>/oom_score_adj. 1653 1654The value of /proc/<pid>/oom_score_adj may be reduced no lower than the last 1655value set by a CAP_SYS_RESOURCE process. To reduce the value any lower 1656requires CAP_SYS_RESOURCE. 1657 1658 16593.2 /proc/<pid>/oom_score - Display current oom-killer score 1660------------------------------------------------------------- 1661 1662This file can be used to check the current score used by the oom-killer for 1663any given <pid>. Use it together with /proc/<pid>/oom_score_adj to tune which 1664process should be killed in an out-of-memory situation. 1665 1666Please note that the exported value includes oom_score_adj so it is 1667effectively in range [0,2000]. 1668 1669 16703.3 /proc/<pid>/io - Display the IO accounting fields 1671------------------------------------------------------- 1672 1673This file contains IO statistics for each running process. 1674 1675Example 1676~~~~~~~ 1677 1678:: 1679 1680 test:/tmp # dd if=/dev/zero of=/tmp/test.dat & 1681 [1] 3828 1682 1683 test:/tmp # cat /proc/3828/io 1684 rchar: 323934931 1685 wchar: 323929600 1686 syscr: 632687 1687 syscw: 632675 1688 read_bytes: 0 1689 write_bytes: 323932160 1690 cancelled_write_bytes: 0 1691 1692 1693Description 1694~~~~~~~~~~~ 1695 1696rchar 1697^^^^^ 1698 1699I/O counter: chars read 1700The number of bytes which this task has caused to be read from storage. This 1701is simply the sum of bytes which this process passed to read() and pread(). 1702It includes things like tty IO and it is unaffected by whether or not actual 1703physical disk IO was required (the read might have been satisfied from 1704pagecache). 1705 1706 1707wchar 1708^^^^^ 1709 1710I/O counter: chars written 1711The number of bytes which this task has caused, or shall cause to be written 1712to disk. Similar caveats apply here as with rchar. 1713 1714 1715syscr 1716^^^^^ 1717 1718I/O counter: read syscalls 1719Attempt to count the number of read I/O operations, i.e. syscalls like read() 1720and pread(). 1721 1722 1723syscw 1724^^^^^ 1725 1726I/O counter: write syscalls 1727Attempt to count the number of write I/O operations, i.e. syscalls like 1728write() and pwrite(). 1729 1730 1731read_bytes 1732^^^^^^^^^^ 1733 1734I/O counter: bytes read 1735Attempt to count the number of bytes which this process really did cause to 1736be fetched from the storage layer. Done at the submit_bio() level, so it is 1737accurate for block-backed filesystems. <please add status regarding NFS and 1738CIFS at a later time> 1739 1740 1741write_bytes 1742^^^^^^^^^^^ 1743 1744I/O counter: bytes written 1745Attempt to count the number of bytes which this process caused to be sent to 1746the storage layer. This is done at page-dirtying time. 1747 1748 1749cancelled_write_bytes 1750^^^^^^^^^^^^^^^^^^^^^ 1751 1752The big inaccuracy here is truncate. If a process writes 1MB to a file and 1753then deletes the file, it will in fact perform no writeout. But it will have 1754been accounted as having caused 1MB of write. 1755In other words: The number of bytes which this process caused to not happen, 1756by truncating pagecache. A task can cause "negative" IO too. If this task 1757truncates some dirty pagecache, some IO which another task has been accounted 1758for (in its write_bytes) will not be happening. We _could_ just subtract that 1759from the truncating task's write_bytes, but there is information loss in doing 1760that. 1761 1762 1763.. Note:: 1764 1765 At its current implementation state, this is a bit racy on 32-bit machines: 1766 if process A reads process B's /proc/pid/io while process B is updating one 1767 of those 64-bit counters, process A could see an intermediate result. 1768 1769 1770More information about this can be found within the taskstats documentation in 1771Documentation/accounting. 1772 17733.4 /proc/<pid>/coredump_filter - Core dump filtering settings 1774--------------------------------------------------------------- 1775When a process is dumped, all anonymous memory is written to a core file as 1776long as the size of the core file isn't limited. But sometimes we don't want 1777to dump some memory segments, for example, huge shared memory or DAX. 1778Conversely, sometimes we want to save file-backed memory segments into a core 1779file, not only the individual files. 1780 1781/proc/<pid>/coredump_filter allows you to customize which memory segments 1782will be dumped when the <pid> process is dumped. coredump_filter is a bitmask 1783of memory types. If a bit of the bitmask is set, memory segments of the 1784corresponding memory type are dumped, otherwise they are not dumped. 1785 1786The following 9 memory types are supported: 1787 1788 - (bit 0) anonymous private memory 1789 - (bit 1) anonymous shared memory 1790 - (bit 2) file-backed private memory 1791 - (bit 3) file-backed shared memory 1792 - (bit 4) ELF header pages in file-backed private memory areas (it is 1793 effective only if the bit 2 is cleared) 1794 - (bit 5) hugetlb private memory 1795 - (bit 6) hugetlb shared memory 1796 - (bit 7) DAX private memory 1797 - (bit 8) DAX shared memory 1798 1799 Note that MMIO pages such as frame buffer are never dumped and vDSO pages 1800 are always dumped regardless of the bitmask status. 1801 1802 Note that bits 0-4 don't affect hugetlb or DAX memory. hugetlb memory is 1803 only affected by bit 5-6, and DAX is only affected by bits 7-8. 1804 1805The default value of coredump_filter is 0x33; this means all anonymous memory 1806segments, ELF header pages and hugetlb private memory are dumped. 1807 1808If you don't want to dump all shared memory segments attached to pid 1234, 1809write 0x31 to the process's proc file:: 1810 1811 $ echo 0x31 > /proc/1234/coredump_filter 1812 1813When a new process is created, the process inherits the bitmask status from its 1814parent. It is useful to set up coredump_filter before the program runs. 1815For example:: 1816 1817 $ echo 0x7 > /proc/self/coredump_filter 1818 $ ./some_program 1819 18203.5 /proc/<pid>/mountinfo - Information about mounts 1821-------------------------------------------------------- 1822 1823This file contains lines of the form:: 1824 1825 36 35 98:0 /mnt1 /mnt2 rw,noatime master:1 - ext3 /dev/root rw,errors=continue 1826 (1)(2)(3) (4) (5) (6) (n…m) (m+1)(m+2) (m+3) (m+4) 1827 1828 (1) mount ID: unique identifier of the mount (may be reused after umount) 1829 (2) parent ID: ID of parent (or of self for the top of the mount tree) 1830 (3) major:minor: value of st_dev for files on filesystem 1831 (4) root: root of the mount within the filesystem 1832 (5) mount point: mount point relative to the process's root 1833 (6) mount options: per mount options 1834 (n…m) optional fields: zero or more fields of the form "tag[:value]" 1835 (m+1) separator: marks the end of the optional fields 1836 (m+2) filesystem type: name of filesystem of the form "type[.subtype]" 1837 (m+3) mount source: filesystem specific information or "none" 1838 (m+4) super options: per super block options 1839 1840Parsers should ignore all unrecognised optional fields. Currently the 1841possible optional fields are: 1842 1843================ ============================================================== 1844shared:X mount is shared in peer group X 1845master:X mount is slave to peer group X 1846propagate_from:X mount is slave and receives propagation from peer group X [#]_ 1847unbindable mount is unbindable 1848================ ============================================================== 1849 1850.. [#] X is the closest dominant peer group under the process's root. If 1851 X is the immediate master of the mount, or if there's no dominant peer 1852 group under the same root, then only the "master:X" field is present 1853 and not the "propagate_from:X" field. 1854 1855For more information on mount propagation see: 1856 1857 Documentation/filesystems/sharedsubtree.rst 1858 1859 18603.6 /proc/<pid>/comm & /proc/<pid>/task/<tid>/comm 1861-------------------------------------------------------- 1862These files provide a method to access a task's comm value. It also allows for 1863a task to set its own or one of its thread siblings comm value. The comm value 1864is limited in size compared to the cmdline value, so writing anything longer 1865then the kernel's TASK_COMM_LEN (currently 16 chars) will result in a truncated 1866comm value. 1867 1868 18693.7 /proc/<pid>/task/<tid>/children - Information about task children 1870------------------------------------------------------------------------- 1871This file provides a fast way to retrieve first level children pids 1872of a task pointed by <pid>/<tid> pair. The format is a space separated 1873stream of pids. 1874 1875Note the "first level" here -- if a child has its own children they will 1876not be listed here; one needs to read /proc/<children-pid>/task/<tid>/children 1877to obtain the descendants. 1878 1879Since this interface is intended to be fast and cheap it doesn't 1880guarantee to provide precise results and some children might be 1881skipped, especially if they've exited right after we printed their 1882pids, so one needs to either stop or freeze processes being inspected 1883if precise results are needed. 1884 1885 18863.8 /proc/<pid>/fdinfo/<fd> - Information about opened file 1887--------------------------------------------------------------- 1888This file provides information associated with an opened file. The regular 1889files have at least four fields -- 'pos', 'flags', 'mnt_id' and 'ino'. 1890The 'pos' represents the current offset of the opened file in decimal 1891form [see lseek(2) for details], 'flags' denotes the octal O_xxx mask the 1892file has been created with [see open(2) for details] and 'mnt_id' represents 1893mount ID of the file system containing the opened file [see 3.5 1894/proc/<pid>/mountinfo for details]. 'ino' represents the inode number of 1895the file. 1896 1897A typical output is:: 1898 1899 pos: 0 1900 flags: 0100002 1901 mnt_id: 19 1902 ino: 63107 1903 1904All locks associated with a file descriptor are shown in its fdinfo too:: 1905 1906 lock: 1: FLOCK ADVISORY WRITE 359 00:13:11691 0 EOF 1907 1908The files such as eventfd, fsnotify, signalfd, epoll among the regular pos/flags 1909pair provide additional information particular to the objects they represent. 1910 1911Eventfd files 1912~~~~~~~~~~~~~ 1913 1914:: 1915 1916 pos: 0 1917 flags: 04002 1918 mnt_id: 9 1919 ino: 63107 1920 eventfd-count: 5a 1921 1922where 'eventfd-count' is hex value of a counter. 1923 1924Signalfd files 1925~~~~~~~~~~~~~~ 1926 1927:: 1928 1929 pos: 0 1930 flags: 04002 1931 mnt_id: 9 1932 ino: 63107 1933 sigmask: 0000000000000200 1934 1935where 'sigmask' is hex value of the signal mask associated 1936with a file. 1937 1938Epoll files 1939~~~~~~~~~~~ 1940 1941:: 1942 1943 pos: 0 1944 flags: 02 1945 mnt_id: 9 1946 ino: 63107 1947 tfd: 5 events: 1d data: ffffffffffffffff pos:0 ino:61af sdev:7 1948 1949where 'tfd' is a target file descriptor number in decimal form, 1950'events' is events mask being watched and the 'data' is data 1951associated with a target [see epoll(7) for more details]. 1952 1953The 'pos' is current offset of the target file in decimal form 1954[see lseek(2)], 'ino' and 'sdev' are inode and device numbers 1955where target file resides, all in hex format. 1956 1957Fsnotify files 1958~~~~~~~~~~~~~~ 1959For inotify files the format is the following:: 1960 1961 pos: 0 1962 flags: 02000000 1963 mnt_id: 9 1964 ino: 63107 1965 inotify wd:3 ino:9e7e sdev:800013 mask:800afce ignored_mask:0 fhandle-bytes:8 fhandle-type:1 f_handle:7e9e0000640d1b6d 1966 1967where 'wd' is a watch descriptor in decimal form, i.e. a target file 1968descriptor number, 'ino' and 'sdev' are inode and device where the 1969target file resides and the 'mask' is the mask of events, all in hex 1970form [see inotify(7) for more details]. 1971 1972If the kernel was built with exportfs support, the path to the target 1973file is encoded as a file handle. The file handle is provided by three 1974fields 'fhandle-bytes', 'fhandle-type' and 'f_handle', all in hex 1975format. 1976 1977If the kernel is built without exportfs support the file handle won't be 1978printed out. 1979 1980If there is no inotify mark attached yet the 'inotify' line will be omitted. 1981 1982For fanotify files the format is:: 1983 1984 pos: 0 1985 flags: 02 1986 mnt_id: 9 1987 ino: 63107 1988 fanotify flags:10 event-flags:0 1989 fanotify mnt_id:12 mflags:40 mask:38 ignored_mask:40000003 1990 fanotify ino:4f969 sdev:800013 mflags:0 mask:3b ignored_mask:40000000 fhandle-bytes:8 fhandle-type:1 f_handle:69f90400c275b5b4 1991 1992where fanotify 'flags' and 'event-flags' are values used in fanotify_init 1993call, 'mnt_id' is the mount point identifier, 'mflags' is the value of 1994flags associated with mark which are tracked separately from events 1995mask. 'ino' and 'sdev' are target inode and device, 'mask' is the events 1996mask and 'ignored_mask' is the mask of events which are to be ignored. 1997All are in hex format. Incorporation of 'mflags', 'mask' and 'ignored_mask' 1998provide information about flags and mask used in fanotify_mark 1999call [see fsnotify manpage for details]. 2000 2001While the first three lines are mandatory and always printed, the rest is 2002optional and may be omitted if no marks created yet. 2003 2004Timerfd files 2005~~~~~~~~~~~~~ 2006 2007:: 2008 2009 pos: 0 2010 flags: 02 2011 mnt_id: 9 2012 ino: 63107 2013 clockid: 0 2014 ticks: 0 2015 settime flags: 01 2016 it_value: (0, 49406829) 2017 it_interval: (1, 0) 2018 2019where 'clockid' is the clock type and 'ticks' is the number of the timer expirations 2020that have occurred [see timerfd_create(2) for details]. 'settime flags' are 2021flags in octal form been used to setup the timer [see timerfd_settime(2) for 2022details]. 'it_value' is remaining time until the timer expiration. 2023'it_interval' is the interval for the timer. Note the timer might be set up 2024with TIMER_ABSTIME option which will be shown in 'settime flags', but 'it_value' 2025still exhibits timer's remaining time. 2026 2027DMA Buffer files 2028~~~~~~~~~~~~~~~~ 2029 2030:: 2031 2032 pos: 0 2033 flags: 04002 2034 mnt_id: 9 2035 ino: 63107 2036 size: 32768 2037 count: 2 2038 exp_name: system-heap 2039 2040where 'size' is the size of the DMA buffer in bytes. 'count' is the file count of 2041the DMA buffer file. 'exp_name' is the name of the DMA buffer exporter. 2042 20433.9 /proc/<pid>/map_files - Information about memory mapped files 2044--------------------------------------------------------------------- 2045This directory contains symbolic links which represent memory mapped files 2046the process is maintaining. Example output:: 2047 2048 | lr-------- 1 root root 64 Jan 27 11:24 333c600000-333c620000 -> /usr/lib64/ld-2.18.so 2049 | lr-------- 1 root root 64 Jan 27 11:24 333c81f000-333c820000 -> /usr/lib64/ld-2.18.so 2050 | lr-------- 1 root root 64 Jan 27 11:24 333c820000-333c821000 -> /usr/lib64/ld-2.18.so 2051 | ... 2052 | lr-------- 1 root root 64 Jan 27 11:24 35d0421000-35d0422000 -> /usr/lib64/libselinux.so.1 2053 | lr-------- 1 root root 64 Jan 27 11:24 400000-41a000 -> /usr/bin/ls 2054 2055The name of a link represents the virtual memory bounds of a mapping, i.e. 2056vm_area_struct::vm_start-vm_area_struct::vm_end. 2057 2058The main purpose of the map_files is to retrieve a set of memory mapped 2059files in a fast way instead of parsing /proc/<pid>/maps or 2060/proc/<pid>/smaps, both of which contain many more records. At the same 2061time one can open(2) mappings from the listings of two processes and 2062comparing their inode numbers to figure out which anonymous memory areas 2063are actually shared. 2064 20653.10 /proc/<pid>/timerslack_ns - Task timerslack value 2066--------------------------------------------------------- 2067This file provides the value of the task's timerslack value in nanoseconds. 2068This value specifies an amount of time that normal timers may be deferred 2069in order to coalesce timers and avoid unnecessary wakeups. 2070 2071This allows a task's interactivity vs power consumption tradeoff to be 2072adjusted. 2073 2074Writing 0 to the file will set the task's timerslack to the default value. 2075 2076Valid values are from 0 - ULLONG_MAX 2077 2078An application setting the value must have PTRACE_MODE_ATTACH_FSCREDS level 2079permissions on the task specified to change its timerslack_ns value. 2080 20813.11 /proc/<pid>/patch_state - Livepatch patch operation state 2082----------------------------------------------------------------- 2083When CONFIG_LIVEPATCH is enabled, this file displays the value of the 2084patch state for the task. 2085 2086A value of '-1' indicates that no patch is in transition. 2087 2088A value of '0' indicates that a patch is in transition and the task is 2089unpatched. If the patch is being enabled, then the task hasn't been 2090patched yet. If the patch is being disabled, then the task has already 2091been unpatched. 2092 2093A value of '1' indicates that a patch is in transition and the task is 2094patched. If the patch is being enabled, then the task has already been 2095patched. If the patch is being disabled, then the task hasn't been 2096unpatched yet. 2097 20983.12 /proc/<pid>/arch_status - task architecture specific status 2099------------------------------------------------------------------- 2100When CONFIG_PROC_PID_ARCH_STATUS is enabled, this file displays the 2101architecture specific status of the task. 2102 2103Example 2104~~~~~~~ 2105 2106:: 2107 2108 $ cat /proc/6753/arch_status 2109 AVX512_elapsed_ms: 8 2110 2111Description 2112~~~~~~~~~~~ 2113 2114x86 specific entries 2115~~~~~~~~~~~~~~~~~~~~~ 2116 2117AVX512_elapsed_ms 2118^^^^^^^^^^^^^^^^^^ 2119 2120 If AVX512 is supported on the machine, this entry shows the milliseconds 2121 elapsed since the last time AVX512 usage was recorded. The recording 2122 happens on a best effort basis when a task is scheduled out. This means 2123 that the value depends on two factors: 2124 2125 1) The time which the task spent on the CPU without being scheduled 2126 out. With CPU isolation and a single runnable task this can take 2127 several seconds. 2128 2129 2) The time since the task was scheduled out last. Depending on the 2130 reason for being scheduled out (time slice exhausted, syscall ...) 2131 this can be arbitrary long time. 2132 2133 As a consequence the value cannot be considered precise and authoritative 2134 information. The application which uses this information has to be aware 2135 of the overall scenario on the system in order to determine whether a 2136 task is a real AVX512 user or not. Precise information can be obtained 2137 with performance counters. 2138 2139 A special value of '-1' indicates that no AVX512 usage was recorded, thus 2140 the task is unlikely an AVX512 user, but depends on the workload and the 2141 scheduling scenario, it also could be a false negative mentioned above. 2142 2143Chapter 4: Configuring procfs 2144============================= 2145 21464.1 Mount options 2147--------------------- 2148 2149The following mount options are supported: 2150 2151 ========= ======================================================== 2152 hidepid= Set /proc/<pid>/ access mode. 2153 gid= Set the group authorized to learn processes information. 2154 subset= Show only the specified subset of procfs. 2155 ========= ======================================================== 2156 2157hidepid=off or hidepid=0 means classic mode - everybody may access all 2158/proc/<pid>/ directories (default). 2159 2160hidepid=noaccess or hidepid=1 means users may not access any /proc/<pid>/ 2161directories but their own. Sensitive files like cmdline, sched*, status are now 2162protected against other users. This makes it impossible to learn whether any 2163user runs specific program (given the program doesn't reveal itself by its 2164behaviour). As an additional bonus, as /proc/<pid>/cmdline is unaccessible for 2165other users, poorly written programs passing sensitive information via program 2166arguments are now protected against local eavesdroppers. 2167 2168hidepid=invisible or hidepid=2 means hidepid=1 plus all /proc/<pid>/ will be 2169fully invisible to other users. It doesn't mean that it hides a fact whether a 2170process with a specific pid value exists (it can be learned by other means, e.g. 2171by "kill -0 $PID"), but it hides process' uid and gid, which may be learned by 2172stat()'ing /proc/<pid>/ otherwise. It greatly complicates an intruder's task of 2173gathering information about running processes, whether some daemon runs with 2174elevated privileges, whether other user runs some sensitive program, whether 2175other users run any program at all, etc. 2176 2177hidepid=ptraceable or hidepid=4 means that procfs should only contain 2178/proc/<pid>/ directories that the caller can ptrace. 2179 2180gid= defines a group authorized to learn processes information otherwise 2181prohibited by hidepid=. If you use some daemon like identd which needs to learn 2182information about processes information, just add identd to this group. 2183 2184subset=pid hides all top level files and directories in the procfs that 2185are not related to tasks. 2186 2187Chapter 5: Filesystem behavior 2188============================== 2189 2190Originally, before the advent of pid namepsace, procfs was a global file 2191system. It means that there was only one procfs instance in the system. 2192 2193When pid namespace was added, a separate procfs instance was mounted in 2194each pid namespace. So, procfs mount options are global among all 2195mountpoints within the same namespace:: 2196 2197 # grep ^proc /proc/mounts 2198 proc /proc proc rw,relatime,hidepid=2 0 0 2199 2200 # strace -e mount mount -o hidepid=1 -t proc proc /tmp/proc 2201 mount("proc", "/tmp/proc", "proc", 0, "hidepid=1") = 0 2202 +++ exited with 0 +++ 2203 2204 # grep ^proc /proc/mounts 2205 proc /proc proc rw,relatime,hidepid=2 0 0 2206 proc /tmp/proc proc rw,relatime,hidepid=2 0 0 2207 2208and only after remounting procfs mount options will change at all 2209mountpoints:: 2210 2211 # mount -o remount,hidepid=1 -t proc proc /tmp/proc 2212 2213 # grep ^proc /proc/mounts 2214 proc /proc proc rw,relatime,hidepid=1 0 0 2215 proc /tmp/proc proc rw,relatime,hidepid=1 0 0 2216 2217This behavior is different from the behavior of other filesystems. 2218 2219The new procfs behavior is more like other filesystems. Each procfs mount 2220creates a new procfs instance. Mount options affect own procfs instance. 2221It means that it became possible to have several procfs instances 2222displaying tasks with different filtering options in one pid namespace:: 2223 2224 # mount -o hidepid=invisible -t proc proc /proc 2225 # mount -o hidepid=noaccess -t proc proc /tmp/proc 2226 # grep ^proc /proc/mounts 2227 proc /proc proc rw,relatime,hidepid=invisible 0 0 2228 proc /tmp/proc proc rw,relatime,hidepid=noaccess 0 0 2229