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 voluntary_ctxt_switches: 0 214 nonvoluntary_ctxt_switches: 1 215 216This shows you nearly the same information you would get if you viewed it with 217the ps command. In fact, ps uses the proc file system to obtain its 218information. But you get a more detailed view of the process by reading the 219file /proc/PID/status. It fields are described in table 1-2. 220 221The statm file contains more detailed information about the process 222memory usage. Its seven fields are explained in Table 1-3. The stat file 223contains detailed information about the process itself. Its fields are 224explained in Table 1-4. 225 226(for SMP CONFIG users) 227 228For making accounting scalable, RSS related information are handled in an 229asynchronous manner and the value may not be very precise. To see a precise 230snapshot of a moment, you can see /proc/<pid>/smaps file and scan page table. 231It's slow but very precise. 232 233.. table:: Table 1-2: Contents of the status files (as of 4.19) 234 235 ========================== =================================================== 236 Field Content 237 ========================== =================================================== 238 Name filename of the executable 239 Umask file mode creation mask 240 State state (R is running, S is sleeping, D is sleeping 241 in an uninterruptible wait, Z is zombie, 242 T is traced or stopped) 243 Tgid thread group ID 244 Ngid NUMA group ID (0 if none) 245 Pid process id 246 PPid process id of the parent process 247 TracerPid PID of process tracing this process (0 if not) 248 Uid Real, effective, saved set, and file system UIDs 249 Gid Real, effective, saved set, and file system GIDs 250 FDSize number of file descriptor slots currently allocated 251 Groups supplementary group list 252 NStgid descendant namespace thread group ID hierarchy 253 NSpid descendant namespace process ID hierarchy 254 NSpgid descendant namespace process group ID hierarchy 255 NSsid descendant namespace session ID hierarchy 256 VmPeak peak virtual memory size 257 VmSize total program size 258 VmLck locked memory size 259 VmPin pinned memory size 260 VmHWM peak resident set size ("high water mark") 261 VmRSS size of memory portions. It contains the three 262 following parts 263 (VmRSS = RssAnon + RssFile + RssShmem) 264 RssAnon size of resident anonymous memory 265 RssFile size of resident file mappings 266 RssShmem size of resident shmem memory (includes SysV shm, 267 mapping of tmpfs and shared anonymous mappings) 268 VmData size of private data segments 269 VmStk size of stack segments 270 VmExe size of text segment 271 VmLib size of shared library code 272 VmPTE size of page table entries 273 VmSwap amount of swap used by anonymous private data 274 (shmem swap usage is not included) 275 HugetlbPages size of hugetlb memory portions 276 CoreDumping process's memory is currently being dumped 277 (killing the process may lead to a corrupted core) 278 THP_enabled process is allowed to use THP (returns 0 when 279 PR_SET_THP_DISABLE is set on the process 280 Threads number of threads 281 SigQ number of signals queued/max. number for queue 282 SigPnd bitmap of pending signals for the thread 283 ShdPnd bitmap of shared pending signals for the process 284 SigBlk bitmap of blocked signals 285 SigIgn bitmap of ignored signals 286 SigCgt bitmap of caught signals 287 CapInh bitmap of inheritable capabilities 288 CapPrm bitmap of permitted capabilities 289 CapEff bitmap of effective capabilities 290 CapBnd bitmap of capabilities bounding set 291 CapAmb bitmap of ambient capabilities 292 NoNewPrivs no_new_privs, like prctl(PR_GET_NO_NEW_PRIV, ...) 293 Seccomp seccomp mode, like prctl(PR_GET_SECCOMP, ...) 294 Speculation_Store_Bypass speculative store bypass mitigation status 295 Cpus_allowed mask of CPUs on which this process may run 296 Cpus_allowed_list Same as previous, but in "list format" 297 Mems_allowed mask of memory nodes allowed to this process 298 Mems_allowed_list Same as previous, but in "list format" 299 voluntary_ctxt_switches number of voluntary context switches 300 nonvoluntary_ctxt_switches number of non voluntary context switches 301 ========================== =================================================== 302 303 304.. table:: Table 1-3: Contents of the statm files (as of 2.6.8-rc3) 305 306 ======== =============================== ============================== 307 Field Content 308 ======== =============================== ============================== 309 size total program size (pages) (same as VmSize in status) 310 resident size of memory portions (pages) (same as VmRSS in status) 311 shared number of pages that are shared (i.e. backed by a file, same 312 as RssFile+RssShmem in status) 313 trs number of pages that are 'code' (not including libs; broken, 314 includes data segment) 315 lrs number of pages of library (always 0 on 2.6) 316 drs number of pages of data/stack (including libs; broken, 317 includes library text) 318 dt number of dirty pages (always 0 on 2.6) 319 ======== =============================== ============================== 320 321 322.. table:: Table 1-4: Contents of the stat files (as of 2.6.30-rc7) 323 324 ============= =============================================================== 325 Field Content 326 ============= =============================================================== 327 pid process id 328 tcomm filename of the executable 329 state state (R is running, S is sleeping, D is sleeping in an 330 uninterruptible wait, Z is zombie, T is traced or stopped) 331 ppid process id of the parent process 332 pgrp pgrp of the process 333 sid session id 334 tty_nr tty the process uses 335 tty_pgrp pgrp of the tty 336 flags task flags 337 min_flt number of minor faults 338 cmin_flt number of minor faults with child's 339 maj_flt number of major faults 340 cmaj_flt number of major faults with child's 341 utime user mode jiffies 342 stime kernel mode jiffies 343 cutime user mode jiffies with child's 344 cstime kernel mode jiffies with child's 345 priority priority level 346 nice nice level 347 num_threads number of threads 348 it_real_value (obsolete, always 0) 349 start_time time the process started after system boot 350 vsize virtual memory size 351 rss resident set memory size 352 rsslim current limit in bytes on the rss 353 start_code address above which program text can run 354 end_code address below which program text can run 355 start_stack address of the start of the main process stack 356 esp current value of ESP 357 eip current value of EIP 358 pending bitmap of pending signals 359 blocked bitmap of blocked signals 360 sigign bitmap of ignored signals 361 sigcatch bitmap of caught signals 362 0 (place holder, used to be the wchan address, 363 use /proc/PID/wchan instead) 364 0 (place holder) 365 0 (place holder) 366 exit_signal signal to send to parent thread on exit 367 task_cpu which CPU the task is scheduled on 368 rt_priority realtime priority 369 policy scheduling policy (man sched_setscheduler) 370 blkio_ticks time spent waiting for block IO 371 gtime guest time of the task in jiffies 372 cgtime guest time of the task children in jiffies 373 start_data address above which program data+bss is placed 374 end_data address below which program data+bss is placed 375 start_brk address above which program heap can be expanded with brk() 376 arg_start address above which program command line is placed 377 arg_end address below which program command line is placed 378 env_start address above which program environment is placed 379 env_end address below which program environment is placed 380 exit_code the thread's exit_code in the form reported by the waitpid 381 system call 382 ============= =============================================================== 383 384The /proc/PID/maps file contains the currently mapped memory regions and 385their access permissions. 386 387The format is:: 388 389 address perms offset dev inode pathname 390 391 08048000-08049000 r-xp 00000000 03:00 8312 /opt/test 392 08049000-0804a000 rw-p 00001000 03:00 8312 /opt/test 393 0804a000-0806b000 rw-p 00000000 00:00 0 [heap] 394 a7cb1000-a7cb2000 ---p 00000000 00:00 0 395 a7cb2000-a7eb2000 rw-p 00000000 00:00 0 396 a7eb2000-a7eb3000 ---p 00000000 00:00 0 397 a7eb3000-a7ed5000 rw-p 00000000 00:00 0 398 a7ed5000-a8008000 r-xp 00000000 03:00 4222 /lib/libc.so.6 399 a8008000-a800a000 r--p 00133000 03:00 4222 /lib/libc.so.6 400 a800a000-a800b000 rw-p 00135000 03:00 4222 /lib/libc.so.6 401 a800b000-a800e000 rw-p 00000000 00:00 0 402 a800e000-a8022000 r-xp 00000000 03:00 14462 /lib/libpthread.so.0 403 a8022000-a8023000 r--p 00013000 03:00 14462 /lib/libpthread.so.0 404 a8023000-a8024000 rw-p 00014000 03:00 14462 /lib/libpthread.so.0 405 a8024000-a8027000 rw-p 00000000 00:00 0 406 a8027000-a8043000 r-xp 00000000 03:00 8317 /lib/ld-linux.so.2 407 a8043000-a8044000 r--p 0001b000 03:00 8317 /lib/ld-linux.so.2 408 a8044000-a8045000 rw-p 0001c000 03:00 8317 /lib/ld-linux.so.2 409 aff35000-aff4a000 rw-p 00000000 00:00 0 [stack] 410 ffffe000-fffff000 r-xp 00000000 00:00 0 [vdso] 411 412where "address" is the address space in the process that it occupies, "perms" 413is a set of permissions:: 414 415 r = read 416 w = write 417 x = execute 418 s = shared 419 p = private (copy on write) 420 421"offset" is the offset into the mapping, "dev" is the device (major:minor), and 422"inode" is the inode on that device. 0 indicates that no inode is associated 423with the memory region, as the case would be with BSS (uninitialized data). 424The "pathname" shows the name associated file for this mapping. If the mapping 425is not associated with a file: 426 427 ======= ==================================== 428 [heap] the heap of the program 429 [stack] the stack of the main process 430 [vdso] the "virtual dynamic shared object", 431 the kernel system call handler 432 ======= ==================================== 433 434 or if empty, the mapping is anonymous. 435 436The /proc/PID/smaps is an extension based on maps, showing the memory 437consumption for each of the process's mappings. For each mapping (aka Virtual 438Memory Area, or VMA) there is a series of lines such as the following:: 439 440 08048000-080bc000 r-xp 00000000 03:02 13130 /bin/bash 441 442 Size: 1084 kB 443 KernelPageSize: 4 kB 444 MMUPageSize: 4 kB 445 Rss: 892 kB 446 Pss: 374 kB 447 Shared_Clean: 892 kB 448 Shared_Dirty: 0 kB 449 Private_Clean: 0 kB 450 Private_Dirty: 0 kB 451 Referenced: 892 kB 452 Anonymous: 0 kB 453 LazyFree: 0 kB 454 AnonHugePages: 0 kB 455 ShmemPmdMapped: 0 kB 456 Shared_Hugetlb: 0 kB 457 Private_Hugetlb: 0 kB 458 Swap: 0 kB 459 SwapPss: 0 kB 460 KernelPageSize: 4 kB 461 MMUPageSize: 4 kB 462 Locked: 0 kB 463 THPeligible: 0 464 VmFlags: rd ex mr mw me dw 465 466The first of these lines shows the same information as is displayed for the 467mapping in /proc/PID/maps. Following lines show the size of the mapping 468(size); the size of each page allocated when backing a VMA (KernelPageSize), 469which is usually the same as the size in the page table entries; the page size 470used by the MMU when backing a VMA (in most cases, the same as KernelPageSize); 471the amount of the mapping that is currently resident in RAM (RSS); the 472process' proportional share of this mapping (PSS); and the number of clean and 473dirty shared and private pages in the mapping. 474 475The "proportional set size" (PSS) of a process is the count of pages it has 476in memory, where each page is divided by the number of processes sharing it. 477So if a process has 1000 pages all to itself, and 1000 shared with one other 478process, its PSS will be 1500. 479 480Note that even a page which is part of a MAP_SHARED mapping, but has only 481a single pte mapped, i.e. is currently used by only one process, is accounted 482as private and not as shared. 483 484"Referenced" indicates the amount of memory currently marked as referenced or 485accessed. 486 487"Anonymous" shows the amount of memory that does not belong to any file. Even 488a mapping associated with a file may contain anonymous pages: when MAP_PRIVATE 489and a page is modified, the file page is replaced by a private anonymous copy. 490 491"LazyFree" shows the amount of memory which is marked by madvise(MADV_FREE). 492The memory isn't freed immediately with madvise(). It's freed in memory 493pressure if the memory is clean. Please note that the printed value might 494be lower than the real value due to optimizations used in the current 495implementation. If this is not desirable please file a bug report. 496 497"AnonHugePages" shows the ammount of memory backed by transparent hugepage. 498 499"ShmemPmdMapped" shows the ammount of shared (shmem/tmpfs) memory backed by 500huge pages. 501 502"Shared_Hugetlb" and "Private_Hugetlb" show the ammounts of memory backed by 503hugetlbfs page which is *not* counted in "RSS" or "PSS" field for historical 504reasons. And these are not included in {Shared,Private}_{Clean,Dirty} field. 505 506"Swap" shows how much would-be-anonymous memory is also used, but out on swap. 507 508For shmem mappings, "Swap" includes also the size of the mapped (and not 509replaced by copy-on-write) part of the underlying shmem object out on swap. 510"SwapPss" shows proportional swap share of this mapping. Unlike "Swap", this 511does not take into account swapped out page of underlying shmem objects. 512"Locked" indicates whether the mapping is locked in memory or not. 513"THPeligible" indicates whether the mapping is eligible for allocating THP 514pages - 1 if true, 0 otherwise. It just shows the current status. 515 516"VmFlags" field deserves a separate description. This member represents the 517kernel flags associated with the particular virtual memory area in two letter 518encoded manner. The codes are the following: 519 520 == ======================================= 521 rd readable 522 wr writeable 523 ex executable 524 sh shared 525 mr may read 526 mw may write 527 me may execute 528 ms may share 529 gd stack segment growns down 530 pf pure PFN range 531 dw disabled write to the mapped file 532 lo pages are locked in memory 533 io memory mapped I/O area 534 sr sequential read advise provided 535 rr random read advise provided 536 dc do not copy area on fork 537 de do not expand area on remapping 538 ac area is accountable 539 nr swap space is not reserved for the area 540 ht area uses huge tlb pages 541 ar architecture specific flag 542 dd do not include area into core dump 543 sd soft dirty flag 544 mm mixed map area 545 hg huge page advise flag 546 nh no huge page advise flag 547 mg mergable advise flag 548 bt arm64 BTI guarded page 549 == ======================================= 550 551Note that there is no guarantee that every flag and associated mnemonic will 552be present in all further kernel releases. Things get changed, the flags may 553be vanished or the reverse -- new added. Interpretation of their meaning 554might change in future as well. So each consumer of these flags has to 555follow each specific kernel version for the exact semantic. 556 557This file is only present if the CONFIG_MMU kernel configuration option is 558enabled. 559 560Note: reading /proc/PID/maps or /proc/PID/smaps is inherently racy (consistent 561output can be achieved only in the single read call). 562 563This typically manifests when doing partial reads of these files while the 564memory map is being modified. Despite the races, we do provide the following 565guarantees: 566 5671) The mapped addresses never go backwards, which implies no two 568 regions will ever overlap. 5692) If there is something at a given vaddr during the entirety of the 570 life of the smaps/maps walk, there will be some output for it. 571 572The /proc/PID/smaps_rollup file includes the same fields as /proc/PID/smaps, 573but their values are the sums of the corresponding values for all mappings of 574the process. Additionally, it contains these fields: 575 576- Pss_Anon 577- Pss_File 578- Pss_Shmem 579 580They represent the proportional shares of anonymous, file, and shmem pages, as 581described for smaps above. These fields are omitted in smaps since each 582mapping identifies the type (anon, file, or shmem) of all pages it contains. 583Thus all information in smaps_rollup can be derived from smaps, but at a 584significantly higher cost. 585 586The /proc/PID/clear_refs is used to reset the PG_Referenced and ACCESSED/YOUNG 587bits on both physical and virtual pages associated with a process, and the 588soft-dirty bit on pte (see Documentation/admin-guide/mm/soft-dirty.rst 589for details). 590To clear the bits for all the pages associated with the process:: 591 592 > echo 1 > /proc/PID/clear_refs 593 594To clear the bits for the anonymous pages associated with the process:: 595 596 > echo 2 > /proc/PID/clear_refs 597 598To clear the bits for the file mapped pages associated with the process:: 599 600 > echo 3 > /proc/PID/clear_refs 601 602To clear the soft-dirty bit:: 603 604 > echo 4 > /proc/PID/clear_refs 605 606To reset the peak resident set size ("high water mark") to the process's 607current value:: 608 609 > echo 5 > /proc/PID/clear_refs 610 611Any other value written to /proc/PID/clear_refs will have no effect. 612 613The /proc/pid/pagemap gives the PFN, which can be used to find the pageflags 614using /proc/kpageflags and number of times a page is mapped using 615/proc/kpagecount. For detailed explanation, see 616Documentation/admin-guide/mm/pagemap.rst. 617 618The /proc/pid/numa_maps is an extension based on maps, showing the memory 619locality and binding policy, as well as the memory usage (in pages) of 620each mapping. The output follows a general format where mapping details get 621summarized separated by blank spaces, one mapping per each file line:: 622 623 address policy mapping details 624 625 00400000 default file=/usr/local/bin/app mapped=1 active=0 N3=1 kernelpagesize_kB=4 626 00600000 default file=/usr/local/bin/app anon=1 dirty=1 N3=1 kernelpagesize_kB=4 627 3206000000 default file=/lib64/ld-2.12.so mapped=26 mapmax=6 N0=24 N3=2 kernelpagesize_kB=4 628 320621f000 default file=/lib64/ld-2.12.so anon=1 dirty=1 N3=1 kernelpagesize_kB=4 629 3206220000 default file=/lib64/ld-2.12.so anon=1 dirty=1 N3=1 kernelpagesize_kB=4 630 3206221000 default anon=1 dirty=1 N3=1 kernelpagesize_kB=4 631 3206800000 default file=/lib64/libc-2.12.so mapped=59 mapmax=21 active=55 N0=41 N3=18 kernelpagesize_kB=4 632 320698b000 default file=/lib64/libc-2.12.so 633 3206b8a000 default file=/lib64/libc-2.12.so anon=2 dirty=2 N3=2 kernelpagesize_kB=4 634 3206b8e000 default file=/lib64/libc-2.12.so anon=1 dirty=1 N3=1 kernelpagesize_kB=4 635 3206b8f000 default anon=3 dirty=3 active=1 N3=3 kernelpagesize_kB=4 636 7f4dc10a2000 default anon=3 dirty=3 N3=3 kernelpagesize_kB=4 637 7f4dc10b4000 default anon=2 dirty=2 active=1 N3=2 kernelpagesize_kB=4 638 7f4dc1200000 default file=/anon_hugepage\040(deleted) huge anon=1 dirty=1 N3=1 kernelpagesize_kB=2048 639 7fff335f0000 default stack anon=3 dirty=3 N3=3 kernelpagesize_kB=4 640 7fff3369d000 default mapped=1 mapmax=35 active=0 N3=1 kernelpagesize_kB=4 641 642Where: 643 644"address" is the starting address for the mapping; 645 646"policy" reports the NUMA memory policy set for the mapping (see Documentation/admin-guide/mm/numa_memory_policy.rst); 647 648"mapping details" summarizes mapping data such as mapping type, page usage counters, 649node locality page counters (N0 == node0, N1 == node1, ...) and the kernel page 650size, in KB, that is backing the mapping up. 651 6521.2 Kernel data 653--------------- 654 655Similar to the process entries, the kernel data files give information about 656the running kernel. The files used to obtain this information are contained in 657/proc and are listed in Table 1-5. Not all of these will be present in your 658system. It depends on the kernel configuration and the loaded modules, which 659files are there, and which are missing. 660 661.. table:: Table 1-5: Kernel info in /proc 662 663 ============ =============================================================== 664 File Content 665 ============ =============================================================== 666 apm Advanced power management info 667 buddyinfo Kernel memory allocator information (see text) (2.5) 668 bus Directory containing bus specific information 669 cmdline Kernel command line 670 cpuinfo Info about the CPU 671 devices Available devices (block and character) 672 dma Used DMS channels 673 filesystems Supported filesystems 674 driver Various drivers grouped here, currently rtc (2.4) 675 execdomains Execdomains, related to security (2.4) 676 fb Frame Buffer devices (2.4) 677 fs File system parameters, currently nfs/exports (2.4) 678 ide Directory containing info about the IDE subsystem 679 interrupts Interrupt usage 680 iomem Memory map (2.4) 681 ioports I/O port usage 682 irq Masks for irq to cpu affinity (2.4)(smp?) 683 isapnp ISA PnP (Plug&Play) Info (2.4) 684 kcore Kernel core image (can be ELF or A.OUT(deprecated in 2.4)) 685 kmsg Kernel messages 686 ksyms Kernel symbol table 687 loadavg Load average of last 1, 5 & 15 minutes 688 locks Kernel locks 689 meminfo Memory info 690 misc Miscellaneous 691 modules List of loaded modules 692 mounts Mounted filesystems 693 net Networking info (see text) 694 pagetypeinfo Additional page allocator information (see text) (2.5) 695 partitions Table of partitions known to the system 696 pci Deprecated info of PCI bus (new way -> /proc/bus/pci/, 697 decoupled by lspci (2.4) 698 rtc Real time clock 699 scsi SCSI info (see text) 700 slabinfo Slab pool info 701 softirqs softirq usage 702 stat Overall statistics 703 swaps Swap space utilization 704 sys See chapter 2 705 sysvipc Info of SysVIPC Resources (msg, sem, shm) (2.4) 706 tty Info of tty drivers 707 uptime Wall clock since boot, combined idle time of all cpus 708 version Kernel version 709 video bttv info of video resources (2.4) 710 vmallocinfo Show vmalloced areas 711 ============ =============================================================== 712 713You can, for example, check which interrupts are currently in use and what 714they are used for by looking in the file /proc/interrupts:: 715 716 > cat /proc/interrupts 717 CPU0 718 0: 8728810 XT-PIC timer 719 1: 895 XT-PIC keyboard 720 2: 0 XT-PIC cascade 721 3: 531695 XT-PIC aha152x 722 4: 2014133 XT-PIC serial 723 5: 44401 XT-PIC pcnet_cs 724 8: 2 XT-PIC rtc 725 11: 8 XT-PIC i82365 726 12: 182918 XT-PIC PS/2 Mouse 727 13: 1 XT-PIC fpu 728 14: 1232265 XT-PIC ide0 729 15: 7 XT-PIC ide1 730 NMI: 0 731 732In 2.4.* a couple of lines where added to this file LOC & ERR (this time is the 733output of a SMP machine):: 734 735 > cat /proc/interrupts 736 737 CPU0 CPU1 738 0: 1243498 1214548 IO-APIC-edge timer 739 1: 8949 8958 IO-APIC-edge keyboard 740 2: 0 0 XT-PIC cascade 741 5: 11286 10161 IO-APIC-edge soundblaster 742 8: 1 0 IO-APIC-edge rtc 743 9: 27422 27407 IO-APIC-edge 3c503 744 12: 113645 113873 IO-APIC-edge PS/2 Mouse 745 13: 0 0 XT-PIC fpu 746 14: 22491 24012 IO-APIC-edge ide0 747 15: 2183 2415 IO-APIC-edge ide1 748 17: 30564 30414 IO-APIC-level eth0 749 18: 177 164 IO-APIC-level bttv 750 NMI: 2457961 2457959 751 LOC: 2457882 2457881 752 ERR: 2155 753 754NMI is incremented in this case because every timer interrupt generates a NMI 755(Non Maskable Interrupt) which is used by the NMI Watchdog to detect lockups. 756 757LOC is the local interrupt counter of the internal APIC of every CPU. 758 759ERR is incremented in the case of errors in the IO-APIC bus (the bus that 760connects the CPUs in a SMP system. This means that an error has been detected, 761the IO-APIC automatically retry the transmission, so it should not be a big 762problem, but you should read the SMP-FAQ. 763 764In 2.6.2* /proc/interrupts was expanded again. This time the goal was for 765/proc/interrupts to display every IRQ vector in use by the system, not 766just those considered 'most important'. The new vectors are: 767 768THR 769 interrupt raised when a machine check threshold counter 770 (typically counting ECC corrected errors of memory or cache) exceeds 771 a configurable threshold. Only available on some systems. 772 773TRM 774 a thermal event interrupt occurs when a temperature threshold 775 has been exceeded for the CPU. This interrupt may also be generated 776 when the temperature drops back to normal. 777 778SPU 779 a spurious interrupt is some interrupt that was raised then lowered 780 by some IO device before it could be fully processed by the APIC. Hence 781 the APIC sees the interrupt but does not know what device it came from. 782 For this case the APIC will generate the interrupt with a IRQ vector 783 of 0xff. This might also be generated by chipset bugs. 784 785RES, CAL, TLB 786 rescheduling, call and TLB flush interrupts are 787 sent from one CPU to another per the needs of the OS. Typically, 788 their statistics are used by kernel developers and interested users to 789 determine the occurrence of interrupts of the given type. 790 791The above IRQ vectors are displayed only when relevant. For example, 792the threshold vector does not exist on x86_64 platforms. Others are 793suppressed when the system is a uniprocessor. As of this writing, only 794i386 and x86_64 platforms support the new IRQ vector displays. 795 796Of some interest is the introduction of the /proc/irq directory to 2.4. 797It could be used to set IRQ to CPU affinity. This means that you can "hook" an 798IRQ to only one CPU, or to exclude a CPU of handling IRQs. The contents of the 799irq subdir is one subdir for each IRQ, and two files; default_smp_affinity and 800prof_cpu_mask. 801 802For example:: 803 804 > ls /proc/irq/ 805 0 10 12 14 16 18 2 4 6 8 prof_cpu_mask 806 1 11 13 15 17 19 3 5 7 9 default_smp_affinity 807 > ls /proc/irq/0/ 808 smp_affinity 809 810smp_affinity is a bitmask, in which you can specify which CPUs can handle the 811IRQ. You can set it by doing:: 812 813 > echo 1 > /proc/irq/10/smp_affinity 814 815This means that only the first CPU will handle the IRQ, but you can also echo 8165 which means that only the first and third CPU can handle the IRQ. 817 818The contents of each smp_affinity file is the same by default:: 819 820 > cat /proc/irq/0/smp_affinity 821 ffffffff 822 823There is an alternate interface, smp_affinity_list which allows specifying 824a CPU range instead of a bitmask:: 825 826 > cat /proc/irq/0/smp_affinity_list 827 1024-1031 828 829The default_smp_affinity mask applies to all non-active IRQs, which are the 830IRQs which have not yet been allocated/activated, and hence which lack a 831/proc/irq/[0-9]* directory. 832 833The node file on an SMP system shows the node to which the device using the IRQ 834reports itself as being attached. This hardware locality information does not 835include information about any possible driver locality preference. 836 837prof_cpu_mask specifies which CPUs are to be profiled by the system wide 838profiler. Default value is ffffffff (all CPUs if there are only 32 of them). 839 840The way IRQs are routed is handled by the IO-APIC, and it's Round Robin 841between all the CPUs which are allowed to handle it. As usual the kernel has 842more info than you and does a better job than you, so the defaults are the 843best choice for almost everyone. [Note this applies only to those IO-APIC's 844that support "Round Robin" interrupt distribution.] 845 846There are three more important subdirectories in /proc: net, scsi, and sys. 847The general rule is that the contents, or even the existence of these 848directories, depend on your kernel configuration. If SCSI is not enabled, the 849directory scsi may not exist. The same is true with the net, which is there 850only when networking support is present in the running kernel. 851 852The slabinfo file gives information about memory usage at the slab level. 853Linux uses slab pools for memory management above page level in version 2.2. 854Commonly used objects have their own slab pool (such as network buffers, 855directory cache, and so on). 856 857:: 858 859 > cat /proc/buddyinfo 860 861 Node 0, zone DMA 0 4 5 4 4 3 ... 862 Node 0, zone Normal 1 0 0 1 101 8 ... 863 Node 0, zone HighMem 2 0 0 1 1 0 ... 864 865External fragmentation is a problem under some workloads, and buddyinfo is a 866useful tool for helping diagnose these problems. Buddyinfo will give you a 867clue as to how big an area you can safely allocate, or why a previous 868allocation failed. 869 870Each column represents the number of pages of a certain order which are 871available. In this case, there are 0 chunks of 2^0*PAGE_SIZE available in 872ZONE_DMA, 4 chunks of 2^1*PAGE_SIZE in ZONE_DMA, 101 chunks of 2^4*PAGE_SIZE 873available in ZONE_NORMAL, etc... 874 875More information relevant to external fragmentation can be found in 876pagetypeinfo:: 877 878 > cat /proc/pagetypeinfo 879 Page block order: 9 880 Pages per block: 512 881 882 Free pages count per migrate type at order 0 1 2 3 4 5 6 7 8 9 10 883 Node 0, zone DMA, type Unmovable 0 0 0 1 1 1 1 1 1 1 0 884 Node 0, zone DMA, type Reclaimable 0 0 0 0 0 0 0 0 0 0 0 885 Node 0, zone DMA, type Movable 1 1 2 1 2 1 1 0 1 0 2 886 Node 0, zone DMA, type Reserve 0 0 0 0 0 0 0 0 0 1 0 887 Node 0, zone DMA, type Isolate 0 0 0 0 0 0 0 0 0 0 0 888 Node 0, zone DMA32, type Unmovable 103 54 77 1 1 1 11 8 7 1 9 889 Node 0, zone DMA32, type Reclaimable 0 0 2 1 0 0 0 0 1 0 0 890 Node 0, zone DMA32, type Movable 169 152 113 91 77 54 39 13 6 1 452 891 Node 0, zone DMA32, type Reserve 1 2 2 2 2 0 1 1 1 1 0 892 Node 0, zone DMA32, type Isolate 0 0 0 0 0 0 0 0 0 0 0 893 894 Number of blocks type Unmovable Reclaimable Movable Reserve Isolate 895 Node 0, zone DMA 2 0 5 1 0 896 Node 0, zone DMA32 41 6 967 2 0 897 898Fragmentation avoidance in the kernel works by grouping pages of different 899migrate types into the same contiguous regions of memory called page blocks. 900A page block is typically the size of the default hugepage size, e.g. 2MB on 901X86-64. By keeping pages grouped based on their ability to move, the kernel 902can reclaim pages within a page block to satisfy a high-order allocation. 903 904The pagetypinfo begins with information on the size of a page block. It 905then gives the same type of information as buddyinfo except broken down 906by migrate-type and finishes with details on how many page blocks of each 907type exist. 908 909If min_free_kbytes has been tuned correctly (recommendations made by hugeadm 910from libhugetlbfs https://github.com/libhugetlbfs/libhugetlbfs/), one can 911make an estimate of the likely number of huge pages that can be allocated 912at a given point in time. All the "Movable" blocks should be allocatable 913unless memory has been mlock()'d. Some of the Reclaimable blocks should 914also be allocatable although a lot of filesystem metadata may have to be 915reclaimed to achieve this. 916 917 918meminfo 919~~~~~~~ 920 921Provides information about distribution and utilization of memory. This 922varies by architecture and compile options. The following is from a 92316GB PIII, which has highmem enabled. You may not have all of these fields. 924 925:: 926 927 > cat /proc/meminfo 928 929 MemTotal: 16344972 kB 930 MemFree: 13634064 kB 931 MemAvailable: 14836172 kB 932 Buffers: 3656 kB 933 Cached: 1195708 kB 934 SwapCached: 0 kB 935 Active: 891636 kB 936 Inactive: 1077224 kB 937 HighTotal: 15597528 kB 938 HighFree: 13629632 kB 939 LowTotal: 747444 kB 940 LowFree: 4432 kB 941 SwapTotal: 0 kB 942 SwapFree: 0 kB 943 Dirty: 968 kB 944 Writeback: 0 kB 945 AnonPages: 861800 kB 946 Mapped: 280372 kB 947 Shmem: 644 kB 948 KReclaimable: 168048 kB 949 Slab: 284364 kB 950 SReclaimable: 159856 kB 951 SUnreclaim: 124508 kB 952 PageTables: 24448 kB 953 NFS_Unstable: 0 kB 954 Bounce: 0 kB 955 WritebackTmp: 0 kB 956 CommitLimit: 7669796 kB 957 Committed_AS: 100056 kB 958 VmallocTotal: 112216 kB 959 VmallocUsed: 428 kB 960 VmallocChunk: 111088 kB 961 Percpu: 62080 kB 962 HardwareCorrupted: 0 kB 963 AnonHugePages: 49152 kB 964 ShmemHugePages: 0 kB 965 ShmemPmdMapped: 0 kB 966 967MemTotal 968 Total usable RAM (i.e. physical RAM minus a few reserved 969 bits and the kernel binary code) 970MemFree 971 The sum of LowFree+HighFree 972MemAvailable 973 An estimate of how much memory is available for starting new 974 applications, without swapping. Calculated from MemFree, 975 SReclaimable, the size of the file LRU lists, and the low 976 watermarks in each zone. 977 The estimate takes into account that the system needs some 978 page cache to function well, and that not all reclaimable 979 slab will be reclaimable, due to items being in use. The 980 impact of those factors will vary from system to system. 981Buffers 982 Relatively temporary storage for raw disk blocks 983 shouldn't get tremendously large (20MB or so) 984Cached 985 in-memory cache for files read from the disk (the 986 pagecache). Doesn't include SwapCached 987SwapCached 988 Memory that once was swapped out, is swapped back in but 989 still also is in the swapfile (if memory is needed it 990 doesn't need to be swapped out AGAIN because it is already 991 in the swapfile. This saves I/O) 992Active 993 Memory that has been used more recently and usually not 994 reclaimed unless absolutely necessary. 995Inactive 996 Memory which has been less recently used. It is more 997 eligible to be reclaimed for other purposes 998HighTotal, HighFree 999 Highmem is all memory above ~860MB of physical memory. 1000 Highmem areas are for use by userspace programs, or 1001 for the pagecache. The kernel must use tricks to access 1002 this memory, making it slower to access than lowmem. 1003LowTotal, LowFree 1004 Lowmem is memory which can be used for everything that 1005 highmem can be used for, but it is also available for the 1006 kernel's use for its own data structures. Among many 1007 other things, it is where everything from the Slab is 1008 allocated. Bad things happen when you're out of lowmem. 1009SwapTotal 1010 total amount of swap space available 1011SwapFree 1012 Memory which has been evicted from RAM, and is temporarily 1013 on the disk 1014Dirty 1015 Memory which is waiting to get written back to the disk 1016Writeback 1017 Memory which is actively being written back to the disk 1018AnonPages 1019 Non-file backed pages mapped into userspace page tables 1020HardwareCorrupted 1021 The amount of RAM/memory in KB, the kernel identifies as 1022 corrupted. 1023AnonHugePages 1024 Non-file backed huge pages mapped into userspace page tables 1025Mapped 1026 files which have been mmaped, such as libraries 1027Shmem 1028 Total memory used by shared memory (shmem) and tmpfs 1029ShmemHugePages 1030 Memory used by shared memory (shmem) and tmpfs allocated 1031 with huge pages 1032ShmemPmdMapped 1033 Shared memory mapped into userspace with huge pages 1034KReclaimable 1035 Kernel allocations that the kernel will attempt to reclaim 1036 under memory pressure. Includes SReclaimable (below), and other 1037 direct allocations with a shrinker. 1038Slab 1039 in-kernel data structures cache 1040SReclaimable 1041 Part of Slab, that might be reclaimed, such as caches 1042SUnreclaim 1043 Part of Slab, that cannot be reclaimed on memory pressure 1044PageTables 1045 amount of memory dedicated to the lowest level of page 1046 tables. 1047NFS_Unstable 1048 Always zero. Previous counted pages which had been written to 1049 the server, but has not been committed to stable storage. 1050Bounce 1051 Memory used for block device "bounce buffers" 1052WritebackTmp 1053 Memory used by FUSE for temporary writeback buffers 1054CommitLimit 1055 Based on the overcommit ratio ('vm.overcommit_ratio'), 1056 this is the total amount of memory currently available to 1057 be allocated on the system. This limit is only adhered to 1058 if strict overcommit accounting is enabled (mode 2 in 1059 'vm.overcommit_memory'). 1060 1061 The CommitLimit is calculated with the following formula:: 1062 1063 CommitLimit = ([total RAM pages] - [total huge TLB pages]) * 1064 overcommit_ratio / 100 + [total swap pages] 1065 1066 For example, on a system with 1G of physical RAM and 7G 1067 of swap with a `vm.overcommit_ratio` of 30 it would 1068 yield a CommitLimit of 7.3G. 1069 1070 For more details, see the memory overcommit documentation 1071 in vm/overcommit-accounting. 1072Committed_AS 1073 The amount of memory presently allocated on the system. 1074 The committed memory is a sum of all of the memory which 1075 has been allocated by processes, even if it has not been 1076 "used" by them as of yet. A process which malloc()'s 1G 1077 of memory, but only touches 300M of it will show up as 1078 using 1G. This 1G is memory which has been "committed" to 1079 by the VM and can be used at any time by the allocating 1080 application. With strict overcommit enabled on the system 1081 (mode 2 in 'vm.overcommit_memory'), allocations which would 1082 exceed the CommitLimit (detailed above) will not be permitted. 1083 This is useful if one needs to guarantee that processes will 1084 not fail due to lack of memory once that memory has been 1085 successfully allocated. 1086VmallocTotal 1087 total size of vmalloc memory area 1088VmallocUsed 1089 amount of vmalloc area which is used 1090VmallocChunk 1091 largest contiguous block of vmalloc area which is free 1092Percpu 1093 Memory allocated to the percpu allocator used to back percpu 1094 allocations. This stat excludes the cost of metadata. 1095 1096vmallocinfo 1097~~~~~~~~~~~ 1098 1099Provides information about vmalloced/vmaped areas. One line per area, 1100containing the virtual address range of the area, size in bytes, 1101caller information of the creator, and optional information depending 1102on the kind of area: 1103 1104 ========== =================================================== 1105 pages=nr number of pages 1106 phys=addr if a physical address was specified 1107 ioremap I/O mapping (ioremap() and friends) 1108 vmalloc vmalloc() area 1109 vmap vmap()ed pages 1110 user VM_USERMAP area 1111 vpages buffer for pages pointers was vmalloced (huge area) 1112 N<node>=nr (Only on NUMA kernels) 1113 Number of pages allocated on memory node <node> 1114 ========== =================================================== 1115 1116:: 1117 1118 > cat /proc/vmallocinfo 1119 0xffffc20000000000-0xffffc20000201000 2101248 alloc_large_system_hash+0x204 ... 1120 /0x2c0 pages=512 vmalloc N0=128 N1=128 N2=128 N3=128 1121 0xffffc20000201000-0xffffc20000302000 1052672 alloc_large_system_hash+0x204 ... 1122 /0x2c0 pages=256 vmalloc N0=64 N1=64 N2=64 N3=64 1123 0xffffc20000302000-0xffffc20000304000 8192 acpi_tb_verify_table+0x21/0x4f... 1124 phys=7fee8000 ioremap 1125 0xffffc20000304000-0xffffc20000307000 12288 acpi_tb_verify_table+0x21/0x4f... 1126 phys=7fee7000 ioremap 1127 0xffffc2000031d000-0xffffc2000031f000 8192 init_vdso_vars+0x112/0x210 1128 0xffffc2000031f000-0xffffc2000032b000 49152 cramfs_uncompress_init+0x2e ... 1129 /0x80 pages=11 vmalloc N0=3 N1=3 N2=2 N3=3 1130 0xffffc2000033a000-0xffffc2000033d000 12288 sys_swapon+0x640/0xac0 ... 1131 pages=2 vmalloc N1=2 1132 0xffffc20000347000-0xffffc2000034c000 20480 xt_alloc_table_info+0xfe ... 1133 /0x130 [x_tables] pages=4 vmalloc N0=4 1134 0xffffffffa0000000-0xffffffffa000f000 61440 sys_init_module+0xc27/0x1d00 ... 1135 pages=14 vmalloc N2=14 1136 0xffffffffa000f000-0xffffffffa0014000 20480 sys_init_module+0xc27/0x1d00 ... 1137 pages=4 vmalloc N1=4 1138 0xffffffffa0014000-0xffffffffa0017000 12288 sys_init_module+0xc27/0x1d00 ... 1139 pages=2 vmalloc N1=2 1140 0xffffffffa0017000-0xffffffffa0022000 45056 sys_init_module+0xc27/0x1d00 ... 1141 pages=10 vmalloc N0=10 1142 1143 1144softirqs 1145~~~~~~~~ 1146 1147Provides counts of softirq handlers serviced since boot time, for each CPU. 1148 1149:: 1150 1151 > cat /proc/softirqs 1152 CPU0 CPU1 CPU2 CPU3 1153 HI: 0 0 0 0 1154 TIMER: 27166 27120 27097 27034 1155 NET_TX: 0 0 0 17 1156 NET_RX: 42 0 0 39 1157 BLOCK: 0 0 107 1121 1158 TASKLET: 0 0 0 290 1159 SCHED: 27035 26983 26971 26746 1160 HRTIMER: 0 0 0 0 1161 RCU: 1678 1769 2178 2250 1162 1163 11641.3 IDE devices in /proc/ide 1165---------------------------- 1166 1167The subdirectory /proc/ide contains information about all IDE devices of which 1168the kernel is aware. There is one subdirectory for each IDE controller, the 1169file drivers and a link for each IDE device, pointing to the device directory 1170in the controller specific subtree. 1171 1172The file 'drivers' contains general information about the drivers used for the 1173IDE devices:: 1174 1175 > cat /proc/ide/drivers 1176 ide-cdrom version 4.53 1177 ide-disk version 1.08 1178 1179More detailed information can be found in the controller specific 1180subdirectories. These are named ide0, ide1 and so on. Each of these 1181directories contains the files shown in table 1-6. 1182 1183 1184.. table:: Table 1-6: IDE controller info in /proc/ide/ide? 1185 1186 ======= ======================================= 1187 File Content 1188 ======= ======================================= 1189 channel IDE channel (0 or 1) 1190 config Configuration (only for PCI/IDE bridge) 1191 mate Mate name 1192 model Type/Chipset of IDE controller 1193 ======= ======================================= 1194 1195Each device connected to a controller has a separate subdirectory in the 1196controllers directory. The files listed in table 1-7 are contained in these 1197directories. 1198 1199 1200.. table:: Table 1-7: IDE device information 1201 1202 ================ ========================================== 1203 File Content 1204 ================ ========================================== 1205 cache The cache 1206 capacity Capacity of the medium (in 512Byte blocks) 1207 driver driver and version 1208 geometry physical and logical geometry 1209 identify device identify block 1210 media media type 1211 model device identifier 1212 settings device setup 1213 smart_thresholds IDE disk management thresholds 1214 smart_values IDE disk management values 1215 ================ ========================================== 1216 1217The most interesting file is ``settings``. This file contains a nice 1218overview of the drive parameters:: 1219 1220 # cat /proc/ide/ide0/hda/settings 1221 name value min max mode 1222 ---- ----- --- --- ---- 1223 bios_cyl 526 0 65535 rw 1224 bios_head 255 0 255 rw 1225 bios_sect 63 0 63 rw 1226 breada_readahead 4 0 127 rw 1227 bswap 0 0 1 r 1228 file_readahead 72 0 2097151 rw 1229 io_32bit 0 0 3 rw 1230 keepsettings 0 0 1 rw 1231 max_kb_per_request 122 1 127 rw 1232 multcount 0 0 8 rw 1233 nice1 1 0 1 rw 1234 nowerr 0 0 1 rw 1235 pio_mode write-only 0 255 w 1236 slow 0 0 1 rw 1237 unmaskirq 0 0 1 rw 1238 using_dma 0 0 1 rw 1239 1240 12411.4 Networking info in /proc/net 1242-------------------------------- 1243 1244The subdirectory /proc/net follows the usual pattern. Table 1-8 shows the 1245additional values you get for IP version 6 if you configure the kernel to 1246support this. Table 1-9 lists the files and their meaning. 1247 1248 1249.. table:: Table 1-8: IPv6 info in /proc/net 1250 1251 ========== ===================================================== 1252 File Content 1253 ========== ===================================================== 1254 udp6 UDP sockets (IPv6) 1255 tcp6 TCP sockets (IPv6) 1256 raw6 Raw device statistics (IPv6) 1257 igmp6 IP multicast addresses, which this host joined (IPv6) 1258 if_inet6 List of IPv6 interface addresses 1259 ipv6_route Kernel routing table for IPv6 1260 rt6_stats Global IPv6 routing tables statistics 1261 sockstat6 Socket statistics (IPv6) 1262 snmp6 Snmp data (IPv6) 1263 ========== ===================================================== 1264 1265.. table:: Table 1-9: Network info in /proc/net 1266 1267 ============= ================================================================ 1268 File Content 1269 ============= ================================================================ 1270 arp Kernel ARP table 1271 dev network devices with statistics 1272 dev_mcast the Layer2 multicast groups a device is listening too 1273 (interface index, label, number of references, number of bound 1274 addresses). 1275 dev_stat network device status 1276 ip_fwchains Firewall chain linkage 1277 ip_fwnames Firewall chain names 1278 ip_masq Directory containing the masquerading tables 1279 ip_masquerade Major masquerading table 1280 netstat Network statistics 1281 raw raw device statistics 1282 route Kernel routing table 1283 rpc Directory containing rpc info 1284 rt_cache Routing cache 1285 snmp SNMP data 1286 sockstat Socket statistics 1287 tcp TCP sockets 1288 udp UDP sockets 1289 unix UNIX domain sockets 1290 wireless Wireless interface data (Wavelan etc) 1291 igmp IP multicast addresses, which this host joined 1292 psched Global packet scheduler parameters. 1293 netlink List of PF_NETLINK sockets 1294 ip_mr_vifs List of multicast virtual interfaces 1295 ip_mr_cache List of multicast routing cache 1296 ============= ================================================================ 1297 1298You can use this information to see which network devices are available in 1299your system and how much traffic was routed over those devices:: 1300 1301 > cat /proc/net/dev 1302 Inter-|Receive |[... 1303 face |bytes packets errs drop fifo frame compressed multicast|[... 1304 lo: 908188 5596 0 0 0 0 0 0 [... 1305 ppp0:15475140 20721 410 0 0 410 0 0 [... 1306 eth0: 614530 7085 0 0 0 0 0 1 [... 1307 1308 ...] Transmit 1309 ...] bytes packets errs drop fifo colls carrier compressed 1310 ...] 908188 5596 0 0 0 0 0 0 1311 ...] 1375103 17405 0 0 0 0 0 0 1312 ...] 1703981 5535 0 0 0 3 0 0 1313 1314In addition, each Channel Bond interface has its own directory. For 1315example, the bond0 device will have a directory called /proc/net/bond0/. 1316It will contain information that is specific to that bond, such as the 1317current slaves of the bond, the link status of the slaves, and how 1318many times the slaves link has failed. 1319 13201.5 SCSI info 1321------------- 1322 1323If you have a SCSI host adapter in your system, you'll find a subdirectory 1324named after the driver for this adapter in /proc/scsi. You'll also see a list 1325of all recognized SCSI devices in /proc/scsi:: 1326 1327 >cat /proc/scsi/scsi 1328 Attached devices: 1329 Host: scsi0 Channel: 00 Id: 00 Lun: 00 1330 Vendor: IBM Model: DGHS09U Rev: 03E0 1331 Type: Direct-Access ANSI SCSI revision: 03 1332 Host: scsi0 Channel: 00 Id: 06 Lun: 00 1333 Vendor: PIONEER Model: CD-ROM DR-U06S Rev: 1.04 1334 Type: CD-ROM ANSI SCSI revision: 02 1335 1336 1337The directory named after the driver has one file for each adapter found in 1338the system. These files contain information about the controller, including 1339the used IRQ and the IO address range. The amount of information shown is 1340dependent on the adapter you use. The example shows the output for an Adaptec 1341AHA-2940 SCSI adapter:: 1342 1343 > cat /proc/scsi/aic7xxx/0 1344 1345 Adaptec AIC7xxx driver version: 5.1.19/3.2.4 1346 Compile Options: 1347 TCQ Enabled By Default : Disabled 1348 AIC7XXX_PROC_STATS : Disabled 1349 AIC7XXX_RESET_DELAY : 5 1350 Adapter Configuration: 1351 SCSI Adapter: Adaptec AHA-294X Ultra SCSI host adapter 1352 Ultra Wide Controller 1353 PCI MMAPed I/O Base: 0xeb001000 1354 Adapter SEEPROM Config: SEEPROM found and used. 1355 Adaptec SCSI BIOS: Enabled 1356 IRQ: 10 1357 SCBs: Active 0, Max Active 2, 1358 Allocated 15, HW 16, Page 255 1359 Interrupts: 160328 1360 BIOS Control Word: 0x18b6 1361 Adapter Control Word: 0x005b 1362 Extended Translation: Enabled 1363 Disconnect Enable Flags: 0xffff 1364 Ultra Enable Flags: 0x0001 1365 Tag Queue Enable Flags: 0x0000 1366 Ordered Queue Tag Flags: 0x0000 1367 Default Tag Queue Depth: 8 1368 Tagged Queue By Device array for aic7xxx host instance 0: 1369 {255,255,255,255,255,255,255,255,255,255,255,255,255,255,255,255} 1370 Actual queue depth per device for aic7xxx host instance 0: 1371 {1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1} 1372 Statistics: 1373 (scsi0:0:0:0) 1374 Device using Wide/Sync transfers at 40.0 MByte/sec, offset 8 1375 Transinfo settings: current(12/8/1/0), goal(12/8/1/0), user(12/15/1/0) 1376 Total transfers 160151 (74577 reads and 85574 writes) 1377 (scsi0:0:6:0) 1378 Device using Narrow/Sync transfers at 5.0 MByte/sec, offset 15 1379 Transinfo settings: current(50/15/0/0), goal(50/15/0/0), user(50/15/0/0) 1380 Total transfers 0 (0 reads and 0 writes) 1381 1382 13831.6 Parallel port info in /proc/parport 1384--------------------------------------- 1385 1386The directory /proc/parport contains information about the parallel ports of 1387your system. It has one subdirectory for each port, named after the port 1388number (0,1,2,...). 1389 1390These directories contain the four files shown in Table 1-10. 1391 1392 1393.. table:: Table 1-10: Files in /proc/parport 1394 1395 ========= ==================================================================== 1396 File Content 1397 ========= ==================================================================== 1398 autoprobe Any IEEE-1284 device ID information that has been acquired. 1399 devices list of the device drivers using that port. A + will appear by the 1400 name of the device currently using the port (it might not appear 1401 against any). 1402 hardware Parallel port's base address, IRQ line and DMA channel. 1403 irq IRQ that parport is using for that port. This is in a separate 1404 file to allow you to alter it by writing a new value in (IRQ 1405 number or none). 1406 ========= ==================================================================== 1407 14081.7 TTY info in /proc/tty 1409------------------------- 1410 1411Information about the available and actually used tty's can be found in the 1412directory /proc/tty. You'll find entries for drivers and line disciplines in 1413this directory, as shown in Table 1-11. 1414 1415 1416.. table:: Table 1-11: Files in /proc/tty 1417 1418 ============= ============================================== 1419 File Content 1420 ============= ============================================== 1421 drivers list of drivers and their usage 1422 ldiscs registered line disciplines 1423 driver/serial usage statistic and status of single tty lines 1424 ============= ============================================== 1425 1426To see which tty's are currently in use, you can simply look into the file 1427/proc/tty/drivers:: 1428 1429 > cat /proc/tty/drivers 1430 pty_slave /dev/pts 136 0-255 pty:slave 1431 pty_master /dev/ptm 128 0-255 pty:master 1432 pty_slave /dev/ttyp 3 0-255 pty:slave 1433 pty_master /dev/pty 2 0-255 pty:master 1434 serial /dev/cua 5 64-67 serial:callout 1435 serial /dev/ttyS 4 64-67 serial 1436 /dev/tty0 /dev/tty0 4 0 system:vtmaster 1437 /dev/ptmx /dev/ptmx 5 2 system 1438 /dev/console /dev/console 5 1 system:console 1439 /dev/tty /dev/tty 5 0 system:/dev/tty 1440 unknown /dev/tty 4 1-63 console 1441 1442 14431.8 Miscellaneous kernel statistics in /proc/stat 1444------------------------------------------------- 1445 1446Various pieces of information about kernel activity are available in the 1447/proc/stat file. All of the numbers reported in this file are aggregates 1448since the system first booted. For a quick look, simply cat the file:: 1449 1450 > cat /proc/stat 1451 cpu 2255 34 2290 22625563 6290 127 456 0 0 0 1452 cpu0 1132 34 1441 11311718 3675 127 438 0 0 0 1453 cpu1 1123 0 849 11313845 2614 0 18 0 0 0 1454 intr 114930548 113199788 3 0 5 263 0 4 [... lots more numbers ...] 1455 ctxt 1990473 1456 btime 1062191376 1457 processes 2915 1458 procs_running 1 1459 procs_blocked 0 1460 softirq 183433 0 21755 12 39 1137 231 21459 2263 1461 1462The very first "cpu" line aggregates the numbers in all of the other "cpuN" 1463lines. These numbers identify the amount of time the CPU has spent performing 1464different kinds of work. Time units are in USER_HZ (typically hundredths of a 1465second). The meanings of the columns are as follows, from left to right: 1466 1467- user: normal processes executing in user mode 1468- nice: niced processes executing in user mode 1469- system: processes executing in kernel mode 1470- idle: twiddling thumbs 1471- iowait: In a word, iowait stands for waiting for I/O to complete. But there 1472 are several problems: 1473 1474 1. CPU will not wait for I/O to complete, iowait is the time that a task is 1475 waiting for I/O to complete. When CPU goes into idle state for 1476 outstanding task I/O, another task will be scheduled on this CPU. 1477 2. In a multi-core CPU, the task waiting for I/O to complete is not running 1478 on any CPU, so the iowait of each CPU is difficult to calculate. 1479 3. The value of iowait field in /proc/stat will decrease in certain 1480 conditions. 1481 1482 So, the iowait is not reliable by reading from /proc/stat. 1483- irq: servicing interrupts 1484- softirq: servicing softirqs 1485- steal: involuntary wait 1486- guest: running a normal guest 1487- guest_nice: running a niced guest 1488 1489The "intr" line gives counts of interrupts serviced since boot time, for each 1490of the possible system interrupts. The first column is the total of all 1491interrupts serviced including unnumbered architecture specific interrupts; 1492each subsequent column is the total for that particular numbered interrupt. 1493Unnumbered interrupts are not shown, only summed into the total. 1494 1495The "ctxt" line gives the total number of context switches across all CPUs. 1496 1497The "btime" line gives the time at which the system booted, in seconds since 1498the Unix epoch. 1499 1500The "processes" line gives the number of processes and threads created, which 1501includes (but is not limited to) those created by calls to the fork() and 1502clone() system calls. 1503 1504The "procs_running" line gives the total number of threads that are 1505running or ready to run (i.e., the total number of runnable threads). 1506 1507The "procs_blocked" line gives the number of processes currently blocked, 1508waiting for I/O to complete. 1509 1510The "softirq" line gives counts of softirqs serviced since boot time, for each 1511of the possible system softirqs. The first column is the total of all 1512softirqs serviced; each subsequent column is the total for that particular 1513softirq. 1514 1515 15161.9 Ext4 file system parameters 1517------------------------------- 1518 1519Information about mounted ext4 file systems can be found in 1520/proc/fs/ext4. Each mounted filesystem will have a directory in 1521/proc/fs/ext4 based on its device name (i.e., /proc/fs/ext4/hdc or 1522/proc/fs/ext4/dm-0). The files in each per-device directory are shown 1523in Table 1-12, below. 1524 1525.. table:: Table 1-12: Files in /proc/fs/ext4/<devname> 1526 1527 ============== ========================================================== 1528 File Content 1529 mb_groups details of multiblock allocator buddy cache of free blocks 1530 ============== ========================================================== 1531 15321.10 /proc/consoles 1533------------------- 1534Shows registered system console lines. 1535 1536To see which character device lines are currently used for the system console 1537/dev/console, you may simply look into the file /proc/consoles:: 1538 1539 > cat /proc/consoles 1540 tty0 -WU (ECp) 4:7 1541 ttyS0 -W- (Ep) 4:64 1542 1543The columns are: 1544 1545+--------------------+-------------------------------------------------------+ 1546| device | name of the device | 1547+====================+=======================================================+ 1548| operations | * R = can do read operations | 1549| | * W = can do write operations | 1550| | * U = can do unblank | 1551+--------------------+-------------------------------------------------------+ 1552| flags | * E = it is enabled | 1553| | * C = it is preferred console | 1554| | * B = it is primary boot console | 1555| | * p = it is used for printk buffer | 1556| | * b = it is not a TTY but a Braille device | 1557| | * a = it is safe to use when cpu is offline | 1558+--------------------+-------------------------------------------------------+ 1559| major:minor | major and minor number of the device separated by a | 1560| | colon | 1561+--------------------+-------------------------------------------------------+ 1562 1563Summary 1564------- 1565 1566The /proc file system serves information about the running system. It not only 1567allows access to process data but also allows you to request the kernel status 1568by reading files in the hierarchy. 1569 1570The directory structure of /proc reflects the types of information and makes 1571it easy, if not obvious, where to look for specific data. 1572 1573Chapter 2: Modifying System Parameters 1574====================================== 1575 1576In This Chapter 1577--------------- 1578 1579* Modifying kernel parameters by writing into files found in /proc/sys 1580* Exploring the files which modify certain parameters 1581* Review of the /proc/sys file tree 1582 1583------------------------------------------------------------------------------ 1584 1585A very interesting part of /proc is the directory /proc/sys. This is not only 1586a source of information, it also allows you to change parameters within the 1587kernel. Be very careful when attempting this. You can optimize your system, 1588but you can also cause it to crash. Never alter kernel parameters on a 1589production system. Set up a development machine and test to make sure that 1590everything works the way you want it to. You may have no alternative but to 1591reboot the machine once an error has been made. 1592 1593To change a value, simply echo the new value into the file. 1594You need to be root to do this. You can create your own boot script 1595to perform this every time your system boots. 1596 1597The files in /proc/sys can be used to fine tune and monitor miscellaneous and 1598general things in the operation of the Linux kernel. Since some of the files 1599can inadvertently disrupt your system, it is advisable to read both 1600documentation and source before actually making adjustments. In any case, be 1601very careful when writing to any of these files. The entries in /proc may 1602change slightly between the 2.1.* and the 2.2 kernel, so if there is any doubt 1603review the kernel documentation in the directory /usr/src/linux/Documentation. 1604This chapter is heavily based on the documentation included in the pre 2.2 1605kernels, and became part of it in version 2.2.1 of the Linux kernel. 1606 1607Please see: Documentation/admin-guide/sysctl/ directory for descriptions of these 1608entries. 1609 1610Summary 1611------- 1612 1613Certain aspects of kernel behavior can be modified at runtime, without the 1614need to recompile the kernel, or even to reboot the system. The files in the 1615/proc/sys tree can not only be read, but also modified. You can use the echo 1616command to write value into these files, thereby changing the default settings 1617of the kernel. 1618 1619 1620Chapter 3: Per-process Parameters 1621================================= 1622 16233.1 /proc/<pid>/oom_adj & /proc/<pid>/oom_score_adj- Adjust the oom-killer score 1624-------------------------------------------------------------------------------- 1625 1626These files can be used to adjust the badness heuristic used to select which 1627process gets killed in out of memory (oom) conditions. 1628 1629The badness heuristic assigns a value to each candidate task ranging from 0 1630(never kill) to 1000 (always kill) to determine which process is targeted. The 1631units are roughly a proportion along that range of allowed memory the process 1632may allocate from based on an estimation of its current memory and swap use. 1633For example, if a task is using all allowed memory, its badness score will be 16341000. If it is using half of its allowed memory, its score will be 500. 1635 1636The amount of "allowed" memory depends on the context in which the oom killer 1637was called. If it is due to the memory assigned to the allocating task's cpuset 1638being exhausted, the allowed memory represents the set of mems assigned to that 1639cpuset. If it is due to a mempolicy's node(s) being exhausted, the allowed 1640memory represents the set of mempolicy nodes. If it is due to a memory 1641limit (or swap limit) being reached, the allowed memory is that configured 1642limit. Finally, if it is due to the entire system being out of memory, the 1643allowed memory represents all allocatable resources. 1644 1645The value of /proc/<pid>/oom_score_adj is added to the badness score before it 1646is used to determine which task to kill. Acceptable values range from -1000 1647(OOM_SCORE_ADJ_MIN) to +1000 (OOM_SCORE_ADJ_MAX). This allows userspace to 1648polarize the preference for oom killing either by always preferring a certain 1649task or completely disabling it. The lowest possible value, -1000, is 1650equivalent to disabling oom killing entirely for that task since it will always 1651report a badness score of 0. 1652 1653Consequently, it is very simple for userspace to define the amount of memory to 1654consider for each task. Setting a /proc/<pid>/oom_score_adj value of +500, for 1655example, is roughly equivalent to allowing the remainder of tasks sharing the 1656same system, cpuset, mempolicy, or memory controller resources to use at least 165750% more memory. A value of -500, on the other hand, would be roughly 1658equivalent to discounting 50% of the task's allowed memory from being considered 1659as scoring against the task. 1660 1661For backwards compatibility with previous kernels, /proc/<pid>/oom_adj may also 1662be used to tune the badness score. Its acceptable values range from -16 1663(OOM_ADJUST_MIN) to +15 (OOM_ADJUST_MAX) and a special value of -17 1664(OOM_DISABLE) to disable oom killing entirely for that task. Its value is 1665scaled linearly with /proc/<pid>/oom_score_adj. 1666 1667The value of /proc/<pid>/oom_score_adj may be reduced no lower than the last 1668value set by a CAP_SYS_RESOURCE process. To reduce the value any lower 1669requires CAP_SYS_RESOURCE. 1670 1671 16723.2 /proc/<pid>/oom_score - Display current oom-killer score 1673------------------------------------------------------------- 1674 1675This file can be used to check the current score used by the oom-killer for 1676any given <pid>. Use it together with /proc/<pid>/oom_score_adj to tune which 1677process should be killed in an out-of-memory situation. 1678 1679Please note that the exported value includes oom_score_adj so it is 1680effectively in range [0,2000]. 1681 1682 16833.3 /proc/<pid>/io - Display the IO accounting fields 1684------------------------------------------------------- 1685 1686This file contains IO statistics for each running process. 1687 1688Example 1689~~~~~~~ 1690 1691:: 1692 1693 test:/tmp # dd if=/dev/zero of=/tmp/test.dat & 1694 [1] 3828 1695 1696 test:/tmp # cat /proc/3828/io 1697 rchar: 323934931 1698 wchar: 323929600 1699 syscr: 632687 1700 syscw: 632675 1701 read_bytes: 0 1702 write_bytes: 323932160 1703 cancelled_write_bytes: 0 1704 1705 1706Description 1707~~~~~~~~~~~ 1708 1709rchar 1710^^^^^ 1711 1712I/O counter: chars read 1713The number of bytes which this task has caused to be read from storage. This 1714is simply the sum of bytes which this process passed to read() and pread(). 1715It includes things like tty IO and it is unaffected by whether or not actual 1716physical disk IO was required (the read might have been satisfied from 1717pagecache). 1718 1719 1720wchar 1721^^^^^ 1722 1723I/O counter: chars written 1724The number of bytes which this task has caused, or shall cause to be written 1725to disk. Similar caveats apply here as with rchar. 1726 1727 1728syscr 1729^^^^^ 1730 1731I/O counter: read syscalls 1732Attempt to count the number of read I/O operations, i.e. syscalls like read() 1733and pread(). 1734 1735 1736syscw 1737^^^^^ 1738 1739I/O counter: write syscalls 1740Attempt to count the number of write I/O operations, i.e. syscalls like 1741write() and pwrite(). 1742 1743 1744read_bytes 1745^^^^^^^^^^ 1746 1747I/O counter: bytes read 1748Attempt to count the number of bytes which this process really did cause to 1749be fetched from the storage layer. Done at the submit_bio() level, so it is 1750accurate for block-backed filesystems. <please add status regarding NFS and 1751CIFS at a later time> 1752 1753 1754write_bytes 1755^^^^^^^^^^^ 1756 1757I/O counter: bytes written 1758Attempt to count the number of bytes which this process caused to be sent to 1759the storage layer. This is done at page-dirtying time. 1760 1761 1762cancelled_write_bytes 1763^^^^^^^^^^^^^^^^^^^^^ 1764 1765The big inaccuracy here is truncate. If a process writes 1MB to a file and 1766then deletes the file, it will in fact perform no writeout. But it will have 1767been accounted as having caused 1MB of write. 1768In other words: The number of bytes which this process caused to not happen, 1769by truncating pagecache. A task can cause "negative" IO too. If this task 1770truncates some dirty pagecache, some IO which another task has been accounted 1771for (in its write_bytes) will not be happening. We _could_ just subtract that 1772from the truncating task's write_bytes, but there is information loss in doing 1773that. 1774 1775 1776.. Note:: 1777 1778 At its current implementation state, this is a bit racy on 32-bit machines: 1779 if process A reads process B's /proc/pid/io while process B is updating one 1780 of those 64-bit counters, process A could see an intermediate result. 1781 1782 1783More information about this can be found within the taskstats documentation in 1784Documentation/accounting. 1785 17863.4 /proc/<pid>/coredump_filter - Core dump filtering settings 1787--------------------------------------------------------------- 1788When a process is dumped, all anonymous memory is written to a core file as 1789long as the size of the core file isn't limited. But sometimes we don't want 1790to dump some memory segments, for example, huge shared memory or DAX. 1791Conversely, sometimes we want to save file-backed memory segments into a core 1792file, not only the individual files. 1793 1794/proc/<pid>/coredump_filter allows you to customize which memory segments 1795will be dumped when the <pid> process is dumped. coredump_filter is a bitmask 1796of memory types. If a bit of the bitmask is set, memory segments of the 1797corresponding memory type are dumped, otherwise they are not dumped. 1798 1799The following 9 memory types are supported: 1800 1801 - (bit 0) anonymous private memory 1802 - (bit 1) anonymous shared memory 1803 - (bit 2) file-backed private memory 1804 - (bit 3) file-backed shared memory 1805 - (bit 4) ELF header pages in file-backed private memory areas (it is 1806 effective only if the bit 2 is cleared) 1807 - (bit 5) hugetlb private memory 1808 - (bit 6) hugetlb shared memory 1809 - (bit 7) DAX private memory 1810 - (bit 8) DAX shared memory 1811 1812 Note that MMIO pages such as frame buffer are never dumped and vDSO pages 1813 are always dumped regardless of the bitmask status. 1814 1815 Note that bits 0-4 don't affect hugetlb or DAX memory. hugetlb memory is 1816 only affected by bit 5-6, and DAX is only affected by bits 7-8. 1817 1818The default value of coredump_filter is 0x33; this means all anonymous memory 1819segments, ELF header pages and hugetlb private memory are dumped. 1820 1821If you don't want to dump all shared memory segments attached to pid 1234, 1822write 0x31 to the process's proc file:: 1823 1824 $ echo 0x31 > /proc/1234/coredump_filter 1825 1826When a new process is created, the process inherits the bitmask status from its 1827parent. It is useful to set up coredump_filter before the program runs. 1828For example:: 1829 1830 $ echo 0x7 > /proc/self/coredump_filter 1831 $ ./some_program 1832 18333.5 /proc/<pid>/mountinfo - Information about mounts 1834-------------------------------------------------------- 1835 1836This file contains lines of the form:: 1837 1838 36 35 98:0 /mnt1 /mnt2 rw,noatime master:1 - ext3 /dev/root rw,errors=continue 1839 (1)(2)(3) (4) (5) (6) (7) (8) (9) (10) (11) 1840 1841 (1) mount ID: unique identifier of the mount (may be reused after umount) 1842 (2) parent ID: ID of parent (or of self for the top of the mount tree) 1843 (3) major:minor: value of st_dev for files on filesystem 1844 (4) root: root of the mount within the filesystem 1845 (5) mount point: mount point relative to the process's root 1846 (6) mount options: per mount options 1847 (7) optional fields: zero or more fields of the form "tag[:value]" 1848 (8) separator: marks the end of the optional fields 1849 (9) filesystem type: name of filesystem of the form "type[.subtype]" 1850 (10) mount source: filesystem specific information or "none" 1851 (11) super options: per super block options 1852 1853Parsers should ignore all unrecognised optional fields. Currently the 1854possible optional fields are: 1855 1856================ ============================================================== 1857shared:X mount is shared in peer group X 1858master:X mount is slave to peer group X 1859propagate_from:X mount is slave and receives propagation from peer group X [#]_ 1860unbindable mount is unbindable 1861================ ============================================================== 1862 1863.. [#] X is the closest dominant peer group under the process's root. If 1864 X is the immediate master of the mount, or if there's no dominant peer 1865 group under the same root, then only the "master:X" field is present 1866 and not the "propagate_from:X" field. 1867 1868For more information on mount propagation see: 1869 1870 Documentation/filesystems/sharedsubtree.rst 1871 1872 18733.6 /proc/<pid>/comm & /proc/<pid>/task/<tid>/comm 1874-------------------------------------------------------- 1875These files provide a method to access a task's comm value. It also allows for 1876a task to set its own or one of its thread siblings comm value. The comm value 1877is limited in size compared to the cmdline value, so writing anything longer 1878then the kernel's TASK_COMM_LEN (currently 16 chars) will result in a truncated 1879comm value. 1880 1881 18823.7 /proc/<pid>/task/<tid>/children - Information about task children 1883------------------------------------------------------------------------- 1884This file provides a fast way to retrieve first level children pids 1885of a task pointed by <pid>/<tid> pair. The format is a space separated 1886stream of pids. 1887 1888Note the "first level" here -- if a child has its own children they will 1889not be listed here; one needs to read /proc/<children-pid>/task/<tid>/children 1890to obtain the descendants. 1891 1892Since this interface is intended to be fast and cheap it doesn't 1893guarantee to provide precise results and some children might be 1894skipped, especially if they've exited right after we printed their 1895pids, so one needs to either stop or freeze processes being inspected 1896if precise results are needed. 1897 1898 18993.8 /proc/<pid>/fdinfo/<fd> - Information about opened file 1900--------------------------------------------------------------- 1901This file provides information associated with an opened file. The regular 1902files have at least three fields -- 'pos', 'flags' and 'mnt_id'. The 'pos' 1903represents the current offset of the opened file in decimal form [see lseek(2) 1904for details], 'flags' denotes the octal O_xxx mask the file has been 1905created with [see open(2) for details] and 'mnt_id' represents mount ID of 1906the file system containing the opened file [see 3.5 /proc/<pid>/mountinfo 1907for details]. 1908 1909A typical output is:: 1910 1911 pos: 0 1912 flags: 0100002 1913 mnt_id: 19 1914 1915All locks associated with a file descriptor are shown in its fdinfo too:: 1916 1917 lock: 1: FLOCK ADVISORY WRITE 359 00:13:11691 0 EOF 1918 1919The files such as eventfd, fsnotify, signalfd, epoll among the regular pos/flags 1920pair provide additional information particular to the objects they represent. 1921 1922Eventfd files 1923~~~~~~~~~~~~~ 1924 1925:: 1926 1927 pos: 0 1928 flags: 04002 1929 mnt_id: 9 1930 eventfd-count: 5a 1931 1932where 'eventfd-count' is hex value of a counter. 1933 1934Signalfd files 1935~~~~~~~~~~~~~~ 1936 1937:: 1938 1939 pos: 0 1940 flags: 04002 1941 mnt_id: 9 1942 sigmask: 0000000000000200 1943 1944where 'sigmask' is hex value of the signal mask associated 1945with a file. 1946 1947Epoll files 1948~~~~~~~~~~~ 1949 1950:: 1951 1952 pos: 0 1953 flags: 02 1954 mnt_id: 9 1955 tfd: 5 events: 1d data: ffffffffffffffff pos:0 ino:61af sdev:7 1956 1957where 'tfd' is a target file descriptor number in decimal form, 1958'events' is events mask being watched and the 'data' is data 1959associated with a target [see epoll(7) for more details]. 1960 1961The 'pos' is current offset of the target file in decimal form 1962[see lseek(2)], 'ino' and 'sdev' are inode and device numbers 1963where target file resides, all in hex format. 1964 1965Fsnotify files 1966~~~~~~~~~~~~~~ 1967For inotify files the format is the following:: 1968 1969 pos: 0 1970 flags: 02000000 1971 inotify wd:3 ino:9e7e sdev:800013 mask:800afce ignored_mask:0 fhandle-bytes:8 fhandle-type:1 f_handle:7e9e0000640d1b6d 1972 1973where 'wd' is a watch descriptor in decimal form, i.e. a target file 1974descriptor number, 'ino' and 'sdev' are inode and device where the 1975target file resides and the 'mask' is the mask of events, all in hex 1976form [see inotify(7) for more details]. 1977 1978If the kernel was built with exportfs support, the path to the target 1979file is encoded as a file handle. The file handle is provided by three 1980fields 'fhandle-bytes', 'fhandle-type' and 'f_handle', all in hex 1981format. 1982 1983If the kernel is built without exportfs support the file handle won't be 1984printed out. 1985 1986If there is no inotify mark attached yet the 'inotify' line will be omitted. 1987 1988For fanotify files the format is:: 1989 1990 pos: 0 1991 flags: 02 1992 mnt_id: 9 1993 fanotify flags:10 event-flags:0 1994 fanotify mnt_id:12 mflags:40 mask:38 ignored_mask:40000003 1995 fanotify ino:4f969 sdev:800013 mflags:0 mask:3b ignored_mask:40000000 fhandle-bytes:8 fhandle-type:1 f_handle:69f90400c275b5b4 1996 1997where fanotify 'flags' and 'event-flags' are values used in fanotify_init 1998call, 'mnt_id' is the mount point identifier, 'mflags' is the value of 1999flags associated with mark which are tracked separately from events 2000mask. 'ino' and 'sdev' are target inode and device, 'mask' is the events 2001mask and 'ignored_mask' is the mask of events which are to be ignored. 2002All are in hex format. Incorporation of 'mflags', 'mask' and 'ignored_mask' 2003provide information about flags and mask used in fanotify_mark 2004call [see fsnotify manpage for details]. 2005 2006While the first three lines are mandatory and always printed, the rest is 2007optional and may be omitted if no marks created yet. 2008 2009Timerfd files 2010~~~~~~~~~~~~~ 2011 2012:: 2013 2014 pos: 0 2015 flags: 02 2016 mnt_id: 9 2017 clockid: 0 2018 ticks: 0 2019 settime flags: 01 2020 it_value: (0, 49406829) 2021 it_interval: (1, 0) 2022 2023where 'clockid' is the clock type and 'ticks' is the number of the timer expirations 2024that have occurred [see timerfd_create(2) for details]. 'settime flags' are 2025flags in octal form been used to setup the timer [see timerfd_settime(2) for 2026details]. 'it_value' is remaining time until the timer expiration. 2027'it_interval' is the interval for the timer. Note the timer might be set up 2028with TIMER_ABSTIME option which will be shown in 'settime flags', but 'it_value' 2029still exhibits timer's remaining time. 2030 20313.9 /proc/<pid>/map_files - Information about memory mapped files 2032--------------------------------------------------------------------- 2033This directory contains symbolic links which represent memory mapped files 2034the process is maintaining. Example output:: 2035 2036 | lr-------- 1 root root 64 Jan 27 11:24 333c600000-333c620000 -> /usr/lib64/ld-2.18.so 2037 | lr-------- 1 root root 64 Jan 27 11:24 333c81f000-333c820000 -> /usr/lib64/ld-2.18.so 2038 | lr-------- 1 root root 64 Jan 27 11:24 333c820000-333c821000 -> /usr/lib64/ld-2.18.so 2039 | ... 2040 | lr-------- 1 root root 64 Jan 27 11:24 35d0421000-35d0422000 -> /usr/lib64/libselinux.so.1 2041 | lr-------- 1 root root 64 Jan 27 11:24 400000-41a000 -> /usr/bin/ls 2042 2043The name of a link represents the virtual memory bounds of a mapping, i.e. 2044vm_area_struct::vm_start-vm_area_struct::vm_end. 2045 2046The main purpose of the map_files is to retrieve a set of memory mapped 2047files in a fast way instead of parsing /proc/<pid>/maps or 2048/proc/<pid>/smaps, both of which contain many more records. At the same 2049time one can open(2) mappings from the listings of two processes and 2050comparing their inode numbers to figure out which anonymous memory areas 2051are actually shared. 2052 20533.10 /proc/<pid>/timerslack_ns - Task timerslack value 2054--------------------------------------------------------- 2055This file provides the value of the task's timerslack value in nanoseconds. 2056This value specifies an amount of time that normal timers may be deferred 2057in order to coalesce timers and avoid unnecessary wakeups. 2058 2059This allows a task's interactivity vs power consumption tradeoff to be 2060adjusted. 2061 2062Writing 0 to the file will set the task's timerslack to the default value. 2063 2064Valid values are from 0 - ULLONG_MAX 2065 2066An application setting the value must have PTRACE_MODE_ATTACH_FSCREDS level 2067permissions on the task specified to change its timerslack_ns value. 2068 20693.11 /proc/<pid>/patch_state - Livepatch patch operation state 2070----------------------------------------------------------------- 2071When CONFIG_LIVEPATCH is enabled, this file displays the value of the 2072patch state for the task. 2073 2074A value of '-1' indicates that no patch is in transition. 2075 2076A value of '0' indicates that a patch is in transition and the task is 2077unpatched. If the patch is being enabled, then the task hasn't been 2078patched yet. If the patch is being disabled, then the task has already 2079been unpatched. 2080 2081A value of '1' indicates that a patch is in transition and the task is 2082patched. If the patch is being enabled, then the task has already been 2083patched. If the patch is being disabled, then the task hasn't been 2084unpatched yet. 2085 20863.12 /proc/<pid>/arch_status - task architecture specific status 2087------------------------------------------------------------------- 2088When CONFIG_PROC_PID_ARCH_STATUS is enabled, this file displays the 2089architecture specific status of the task. 2090 2091Example 2092~~~~~~~ 2093 2094:: 2095 2096 $ cat /proc/6753/arch_status 2097 AVX512_elapsed_ms: 8 2098 2099Description 2100~~~~~~~~~~~ 2101 2102x86 specific entries 2103~~~~~~~~~~~~~~~~~~~~~ 2104 2105AVX512_elapsed_ms 2106^^^^^^^^^^^^^^^^^^ 2107 2108 If AVX512 is supported on the machine, this entry shows the milliseconds 2109 elapsed since the last time AVX512 usage was recorded. The recording 2110 happens on a best effort basis when a task is scheduled out. This means 2111 that the value depends on two factors: 2112 2113 1) The time which the task spent on the CPU without being scheduled 2114 out. With CPU isolation and a single runnable task this can take 2115 several seconds. 2116 2117 2) The time since the task was scheduled out last. Depending on the 2118 reason for being scheduled out (time slice exhausted, syscall ...) 2119 this can be arbitrary long time. 2120 2121 As a consequence the value cannot be considered precise and authoritative 2122 information. The application which uses this information has to be aware 2123 of the overall scenario on the system in order to determine whether a 2124 task is a real AVX512 user or not. Precise information can be obtained 2125 with performance counters. 2126 2127 A special value of '-1' indicates that no AVX512 usage was recorded, thus 2128 the task is unlikely an AVX512 user, but depends on the workload and the 2129 scheduling scenario, it also could be a false negative mentioned above. 2130 2131Chapter 4: Configuring procfs 2132============================= 2133 21344.1 Mount options 2135--------------------- 2136 2137The following mount options are supported: 2138 2139 ========= ======================================================== 2140 hidepid= Set /proc/<pid>/ access mode. 2141 gid= Set the group authorized to learn processes information. 2142 subset= Show only the specified subset of procfs. 2143 ========= ======================================================== 2144 2145hidepid=off or hidepid=0 means classic mode - everybody may access all 2146/proc/<pid>/ directories (default). 2147 2148hidepid=noaccess or hidepid=1 means users may not access any /proc/<pid>/ 2149directories but their own. Sensitive files like cmdline, sched*, status are now 2150protected against other users. This makes it impossible to learn whether any 2151user runs specific program (given the program doesn't reveal itself by its 2152behaviour). As an additional bonus, as /proc/<pid>/cmdline is unaccessible for 2153other users, poorly written programs passing sensitive information via program 2154arguments are now protected against local eavesdroppers. 2155 2156hidepid=invisible or hidepid=2 means hidepid=1 plus all /proc/<pid>/ will be 2157fully invisible to other users. It doesn't mean that it hides a fact whether a 2158process with a specific pid value exists (it can be learned by other means, e.g. 2159by "kill -0 $PID"), but it hides process' uid and gid, which may be learned by 2160stat()'ing /proc/<pid>/ otherwise. It greatly complicates an intruder's task of 2161gathering information about running processes, whether some daemon runs with 2162elevated privileges, whether other user runs some sensitive program, whether 2163other users run any program at all, etc. 2164 2165hidepid=ptraceable or hidepid=4 means that procfs should only contain 2166/proc/<pid>/ directories that the caller can ptrace. 2167 2168gid= defines a group authorized to learn processes information otherwise 2169prohibited by hidepid=. If you use some daemon like identd which needs to learn 2170information about processes information, just add identd to this group. 2171 2172subset=pid hides all top level files and directories in the procfs that 2173are not related to tasks. 2174 2175Chapter 5: Filesystem behavior 2176============================== 2177 2178Originally, before the advent of pid namepsace, procfs was a global file 2179system. It means that there was only one procfs instance in the system. 2180 2181When pid namespace was added, a separate procfs instance was mounted in 2182each pid namespace. So, procfs mount options are global among all 2183mountpoints within the same namespace:: 2184 2185 # grep ^proc /proc/mounts 2186 proc /proc proc rw,relatime,hidepid=2 0 0 2187 2188 # strace -e mount mount -o hidepid=1 -t proc proc /tmp/proc 2189 mount("proc", "/tmp/proc", "proc", 0, "hidepid=1") = 0 2190 +++ exited with 0 +++ 2191 2192 # grep ^proc /proc/mounts 2193 proc /proc proc rw,relatime,hidepid=2 0 0 2194 proc /tmp/proc proc rw,relatime,hidepid=2 0 0 2195 2196and only after remounting procfs mount options will change at all 2197mountpoints:: 2198 2199 # mount -o remount,hidepid=1 -t proc proc /tmp/proc 2200 2201 # grep ^proc /proc/mounts 2202 proc /proc proc rw,relatime,hidepid=1 0 0 2203 proc /tmp/proc proc rw,relatime,hidepid=1 0 0 2204 2205This behavior is different from the behavior of other filesystems. 2206 2207The new procfs behavior is more like other filesystems. Each procfs mount 2208creates a new procfs instance. Mount options affect own procfs instance. 2209It means that it became possible to have several procfs instances 2210displaying tasks with different filtering options in one pid namespace:: 2211 2212 # mount -o hidepid=invisible -t proc proc /proc 2213 # mount -o hidepid=noaccess -t proc proc /tmp/proc 2214 # grep ^proc /proc/mounts 2215 proc /proc proc rw,relatime,hidepid=invisible 0 0 2216 proc /tmp/proc proc rw,relatime,hidepid=noaccess 0 0 2217