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 54Preface 55======= 56 570.1 Introduction/Credits 58------------------------ 59 60This documentation is part of a soon (or so we hope) to be released book on 61the SuSE Linux distribution. As there is no complete documentation for the 62/proc file system and we've used many freely available sources to write these 63chapters, it seems only fair to give the work back to the Linux community. 64This work is based on the 2.2.* kernel version and the upcoming 2.4.*. I'm 65afraid it's still far from complete, but we hope it will be useful. As far as 66we know, it is the first 'all-in-one' document about the /proc file system. It 67is focused on the Intel x86 hardware, so if you are looking for PPC, ARM, 68SPARC, AXP, etc., features, you probably won't find what you are looking for. 69It also only covers IPv4 networking, not IPv6 nor other protocols - sorry. But 70additions and patches are welcome and will be added to this document if you 71mail them to Bodo. 72 73We'd like to thank Alan Cox, Rik van Riel, and Alexey Kuznetsov and a lot of 74other people for help compiling this documentation. We'd also like to extend a 75special thank you to Andi Kleen for documentation, which we relied on heavily 76to create this document, as well as the additional information he provided. 77Thanks to everybody else who contributed source or docs to the Linux kernel 78and helped create a great piece of software... :) 79 80If you have any comments, corrections or additions, please don't hesitate to 81contact Bodo Bauer at bb@ricochet.net. We'll be happy to add them to this 82document. 83 84The latest version of this document is available online at 85http://tldp.org/LDP/Linux-Filesystem-Hierarchy/html/proc.html 86 87If the above direction does not works for you, you could try the kernel 88mailing list at linux-kernel@vger.kernel.org and/or try to reach me at 89comandante@zaralinux.com. 90 910.2 Legal Stuff 92--------------- 93 94We don't guarantee the correctness of this document, and if you come to us 95complaining about how you screwed up your system because of incorrect 96documentation, we won't feel responsible... 97 98Chapter 1: Collecting System Information 99======================================== 100 101In This Chapter 102--------------- 103* Investigating the properties of the pseudo file system /proc and its 104 ability to provide information on the running Linux system 105* Examining /proc's structure 106* Uncovering various information about the kernel and the processes running 107 on the system 108 109------------------------------------------------------------------------------ 110 111The proc file system acts as an interface to internal data structures in the 112kernel. It can be used to obtain information about the system and to change 113certain kernel parameters at runtime (sysctl). 114 115First, we'll take a look at the read-only parts of /proc. In Chapter 2, we 116show you how you can use /proc/sys to change settings. 117 1181.1 Process-Specific Subdirectories 119----------------------------------- 120 121The directory /proc contains (among other things) one subdirectory for each 122process running on the system, which is named after the process ID (PID). 123 124The link self points to the process reading the file system. Each process 125subdirectory has the entries listed in Table 1-1. 126 127Note that an open a file descriptor to /proc/<pid> or to any of its 128contained files or subdirectories does not prevent <pid> being reused 129for some other process in the event that <pid> exits. Operations on 130open /proc/<pid> file descriptors corresponding to dead processes 131never act on any new process that the kernel may, through chance, have 132also assigned the process ID <pid>. Instead, operations on these FDs 133usually fail with ESRCH. 134 135.. table:: Table 1-1: Process specific entries in /proc 136 137 ============= =============================================================== 138 File Content 139 ============= =============================================================== 140 clear_refs Clears page referenced bits shown in smaps output 141 cmdline Command line arguments 142 cpu Current and last cpu in which it was executed (2.4)(smp) 143 cwd Link to the current working directory 144 environ Values of environment variables 145 exe Link to the executable of this process 146 fd Directory, which contains all file descriptors 147 maps Memory maps to executables and library files (2.4) 148 mem Memory held by this process 149 root Link to the root directory of this process 150 stat Process status 151 statm Process memory status information 152 status Process status in human readable form 153 wchan Present with CONFIG_KALLSYMS=y: it shows the kernel function 154 symbol the task is blocked in - or "0" if not blocked. 155 pagemap Page table 156 stack Report full stack trace, enable via CONFIG_STACKTRACE 157 smaps An extension based on maps, showing the memory consumption of 158 each mapping and flags associated with it 159 smaps_rollup Accumulated smaps stats for all mappings of the process. This 160 can be derived from smaps, but is faster and more convenient 161 numa_maps An extension based on maps, showing the memory locality and 162 binding policy as well as mem usage (in pages) of each mapping. 163 ============= =============================================================== 164 165For example, to get the status information of a process, all you have to do is 166read the file /proc/PID/status:: 167 168 >cat /proc/self/status 169 Name: cat 170 State: R (running) 171 Tgid: 5452 172 Pid: 5452 173 PPid: 743 174 TracerPid: 0 (2.4) 175 Uid: 501 501 501 501 176 Gid: 100 100 100 100 177 FDSize: 256 178 Groups: 100 14 16 179 VmPeak: 5004 kB 180 VmSize: 5004 kB 181 VmLck: 0 kB 182 VmHWM: 476 kB 183 VmRSS: 476 kB 184 RssAnon: 352 kB 185 RssFile: 120 kB 186 RssShmem: 4 kB 187 VmData: 156 kB 188 VmStk: 88 kB 189 VmExe: 68 kB 190 VmLib: 1412 kB 191 VmPTE: 20 kb 192 VmSwap: 0 kB 193 HugetlbPages: 0 kB 194 CoreDumping: 0 195 THP_enabled: 1 196 Threads: 1 197 SigQ: 0/28578 198 SigPnd: 0000000000000000 199 ShdPnd: 0000000000000000 200 SigBlk: 0000000000000000 201 SigIgn: 0000000000000000 202 SigCgt: 0000000000000000 203 CapInh: 00000000fffffeff 204 CapPrm: 0000000000000000 205 CapEff: 0000000000000000 206 CapBnd: ffffffffffffffff 207 CapAmb: 0000000000000000 208 NoNewPrivs: 0 209 Seccomp: 0 210 Speculation_Store_Bypass: thread vulnerable 211 voluntary_ctxt_switches: 0 212 nonvoluntary_ctxt_switches: 1 213 214This shows you nearly the same information you would get if you viewed it with 215the ps command. In fact, ps uses the proc file system to obtain its 216information. But you get a more detailed view of the process by reading the 217file /proc/PID/status. It fields are described in table 1-2. 218 219The statm file contains more detailed information about the process 220memory usage. Its seven fields are explained in Table 1-3. The stat file 221contains details information about the process itself. Its fields are 222explained in Table 1-4. 223 224(for SMP CONFIG users) 225 226For making accounting scalable, RSS related information are handled in an 227asynchronous manner and the value may not be very precise. To see a precise 228snapshot of a moment, you can see /proc/<pid>/smaps file and scan page table. 229It's slow but very precise. 230 231.. table:: Table 1-2: Contents of the status files (as of 4.19) 232 233 ========================== =================================================== 234 Field Content 235 ========================== =================================================== 236 Name filename of the executable 237 Umask file mode creation mask 238 State state (R is running, S is sleeping, D is sleeping 239 in an uninterruptible wait, Z is zombie, 240 T is traced or stopped) 241 Tgid thread group ID 242 Ngid NUMA group ID (0 if none) 243 Pid process id 244 PPid process id of the parent process 245 TracerPid PID of process tracing this process (0 if not) 246 Uid Real, effective, saved set, and file system UIDs 247 Gid Real, effective, saved set, and file system GIDs 248 FDSize number of file descriptor slots currently allocated 249 Groups supplementary group list 250 NStgid descendant namespace thread group ID hierarchy 251 NSpid descendant namespace process ID hierarchy 252 NSpgid descendant namespace process group ID hierarchy 253 NSsid descendant namespace session ID hierarchy 254 VmPeak peak virtual memory size 255 VmSize total program size 256 VmLck locked memory size 257 VmPin pinned memory size 258 VmHWM peak resident set size ("high water mark") 259 VmRSS size of memory portions. It contains the three 260 following parts 261 (VmRSS = RssAnon + RssFile + RssShmem) 262 RssAnon size of resident anonymous memory 263 RssFile size of resident file mappings 264 RssShmem size of resident shmem memory (includes SysV shm, 265 mapping of tmpfs and shared anonymous mappings) 266 VmData size of private data segments 267 VmStk size of stack segments 268 VmExe size of text segment 269 VmLib size of shared library code 270 VmPTE size of page table entries 271 VmSwap amount of swap used by anonymous private data 272 (shmem swap usage is not included) 273 HugetlbPages size of hugetlb memory portions 274 CoreDumping process's memory is currently being dumped 275 (killing the process may lead to a corrupted core) 276 THP_enabled process is allowed to use THP (returns 0 when 277 PR_SET_THP_DISABLE is set on the process 278 Threads number of threads 279 SigQ number of signals queued/max. number for queue 280 SigPnd bitmap of pending signals for the thread 281 ShdPnd bitmap of shared pending signals for the process 282 SigBlk bitmap of blocked signals 283 SigIgn bitmap of ignored signals 284 SigCgt bitmap of caught signals 285 CapInh bitmap of inheritable capabilities 286 CapPrm bitmap of permitted capabilities 287 CapEff bitmap of effective capabilities 288 CapBnd bitmap of capabilities bounding set 289 CapAmb bitmap of ambient capabilities 290 NoNewPrivs no_new_privs, like prctl(PR_GET_NO_NEW_PRIV, ...) 291 Seccomp seccomp mode, like prctl(PR_GET_SECCOMP, ...) 292 Speculation_Store_Bypass speculative store bypass mitigation status 293 Cpus_allowed mask of CPUs on which this process may run 294 Cpus_allowed_list Same as previous, but in "list format" 295 Mems_allowed mask of memory nodes allowed to this process 296 Mems_allowed_list Same as previous, but in "list format" 297 voluntary_ctxt_switches number of voluntary context switches 298 nonvoluntary_ctxt_switches number of non voluntary context switches 299 ========================== =================================================== 300 301 302.. table:: Table 1-3: Contents of the statm files (as of 2.6.8-rc3) 303 304 ======== =============================== ============================== 305 Field Content 306 ======== =============================== ============================== 307 size total program size (pages) (same as VmSize in status) 308 resident size of memory portions (pages) (same as VmRSS in status) 309 shared number of pages that are shared (i.e. backed by a file, same 310 as RssFile+RssShmem in status) 311 trs number of pages that are 'code' (not including libs; broken, 312 includes data segment) 313 lrs number of pages of library (always 0 on 2.6) 314 drs number of pages of data/stack (including libs; broken, 315 includes library text) 316 dt number of dirty pages (always 0 on 2.6) 317 ======== =============================== ============================== 318 319 320.. table:: Table 1-4: Contents of the stat files (as of 2.6.30-rc7) 321 322 ============= =============================================================== 323 Field Content 324 ============= =============================================================== 325 pid process id 326 tcomm filename of the executable 327 state state (R is running, S is sleeping, D is sleeping in an 328 uninterruptible wait, Z is zombie, T is traced or stopped) 329 ppid process id of the parent process 330 pgrp pgrp of the process 331 sid session id 332 tty_nr tty the process uses 333 tty_pgrp pgrp of the tty 334 flags task flags 335 min_flt number of minor faults 336 cmin_flt number of minor faults with child's 337 maj_flt number of major faults 338 cmaj_flt number of major faults with child's 339 utime user mode jiffies 340 stime kernel mode jiffies 341 cutime user mode jiffies with child's 342 cstime kernel mode jiffies with child's 343 priority priority level 344 nice nice level 345 num_threads number of threads 346 it_real_value (obsolete, always 0) 347 start_time time the process started after system boot 348 vsize virtual memory size 349 rss resident set memory size 350 rsslim current limit in bytes on the rss 351 start_code address above which program text can run 352 end_code address below which program text can run 353 start_stack address of the start of the main process stack 354 esp current value of ESP 355 eip current value of EIP 356 pending bitmap of pending signals 357 blocked bitmap of blocked signals 358 sigign bitmap of ignored signals 359 sigcatch bitmap of caught signals 360 0 (place holder, used to be the wchan address, 361 use /proc/PID/wchan instead) 362 0 (place holder) 363 0 (place holder) 364 exit_signal signal to send to parent thread on exit 365 task_cpu which CPU the task is scheduled on 366 rt_priority realtime priority 367 policy scheduling policy (man sched_setscheduler) 368 blkio_ticks time spent waiting for block IO 369 gtime guest time of the task in jiffies 370 cgtime guest time of the task children in jiffies 371 start_data address above which program data+bss is placed 372 end_data address below which program data+bss is placed 373 start_brk address above which program heap can be expanded with brk() 374 arg_start address above which program command line is placed 375 arg_end address below which program command line is placed 376 env_start address above which program environment is placed 377 env_end address below which program environment is placed 378 exit_code the thread's exit_code in the form reported by the waitpid 379 system call 380 ============= =============================================================== 381 382The /proc/PID/maps file contains the currently mapped memory regions and 383their access permissions. 384 385The format is:: 386 387 address perms offset dev inode pathname 388 389 08048000-08049000 r-xp 00000000 03:00 8312 /opt/test 390 08049000-0804a000 rw-p 00001000 03:00 8312 /opt/test 391 0804a000-0806b000 rw-p 00000000 00:00 0 [heap] 392 a7cb1000-a7cb2000 ---p 00000000 00:00 0 393 a7cb2000-a7eb2000 rw-p 00000000 00:00 0 394 a7eb2000-a7eb3000 ---p 00000000 00:00 0 395 a7eb3000-a7ed5000 rw-p 00000000 00:00 0 396 a7ed5000-a8008000 r-xp 00000000 03:00 4222 /lib/libc.so.6 397 a8008000-a800a000 r--p 00133000 03:00 4222 /lib/libc.so.6 398 a800a000-a800b000 rw-p 00135000 03:00 4222 /lib/libc.so.6 399 a800b000-a800e000 rw-p 00000000 00:00 0 400 a800e000-a8022000 r-xp 00000000 03:00 14462 /lib/libpthread.so.0 401 a8022000-a8023000 r--p 00013000 03:00 14462 /lib/libpthread.so.0 402 a8023000-a8024000 rw-p 00014000 03:00 14462 /lib/libpthread.so.0 403 a8024000-a8027000 rw-p 00000000 00:00 0 404 a8027000-a8043000 r-xp 00000000 03:00 8317 /lib/ld-linux.so.2 405 a8043000-a8044000 r--p 0001b000 03:00 8317 /lib/ld-linux.so.2 406 a8044000-a8045000 rw-p 0001c000 03:00 8317 /lib/ld-linux.so.2 407 aff35000-aff4a000 rw-p 00000000 00:00 0 [stack] 408 ffffe000-fffff000 r-xp 00000000 00:00 0 [vdso] 409 410where "address" is the address space in the process that it occupies, "perms" 411is a set of permissions:: 412 413 r = read 414 w = write 415 x = execute 416 s = shared 417 p = private (copy on write) 418 419"offset" is the offset into the mapping, "dev" is the device (major:minor), and 420"inode" is the inode on that device. 0 indicates that no inode is associated 421with the memory region, as the case would be with BSS (uninitialized data). 422The "pathname" shows the name associated file for this mapping. If the mapping 423is not associated with a file: 424 425 ======= ==================================== 426 [heap] the heap of the program 427 [stack] the stack of the main process 428 [vdso] the "virtual dynamic shared object", 429 the kernel system call handler 430 ======= ==================================== 431 432 or if empty, the mapping is anonymous. 433 434The /proc/PID/smaps is an extension based on maps, showing the memory 435consumption for each of the process's mappings. For each mapping (aka Virtual 436Memory Area, or VMA) there is a series of lines such as the following:: 437 438 08048000-080bc000 r-xp 00000000 03:02 13130 /bin/bash 439 440 Size: 1084 kB 441 KernelPageSize: 4 kB 442 MMUPageSize: 4 kB 443 Rss: 892 kB 444 Pss: 374 kB 445 Shared_Clean: 892 kB 446 Shared_Dirty: 0 kB 447 Private_Clean: 0 kB 448 Private_Dirty: 0 kB 449 Referenced: 892 kB 450 Anonymous: 0 kB 451 LazyFree: 0 kB 452 AnonHugePages: 0 kB 453 ShmemPmdMapped: 0 kB 454 Shared_Hugetlb: 0 kB 455 Private_Hugetlb: 0 kB 456 Swap: 0 kB 457 SwapPss: 0 kB 458 KernelPageSize: 4 kB 459 MMUPageSize: 4 kB 460 Locked: 0 kB 461 THPeligible: 0 462 VmFlags: rd ex mr mw me dw 463 464The first of these lines shows the same information as is displayed for the 465mapping in /proc/PID/maps. Following lines show the size of the mapping 466(size); the size of each page allocated when backing a VMA (KernelPageSize), 467which is usually the same as the size in the page table entries; the page size 468used by the MMU when backing a VMA (in most cases, the same as KernelPageSize); 469the amount of the mapping that is currently resident in RAM (RSS); the 470process' proportional share of this mapping (PSS); and the number of clean and 471dirty shared and private pages in the mapping. 472 473The "proportional set size" (PSS) of a process is the count of pages it has 474in memory, where each page is divided by the number of processes sharing it. 475So if a process has 1000 pages all to itself, and 1000 shared with one other 476process, its PSS will be 1500. 477 478Note that even a page which is part of a MAP_SHARED mapping, but has only 479a single pte mapped, i.e. is currently used by only one process, is accounted 480as private and not as shared. 481 482"Referenced" indicates the amount of memory currently marked as referenced or 483accessed. 484 485"Anonymous" shows the amount of memory that does not belong to any file. Even 486a mapping associated with a file may contain anonymous pages: when MAP_PRIVATE 487and a page is modified, the file page is replaced by a private anonymous copy. 488 489"LazyFree" shows the amount of memory which is marked by madvise(MADV_FREE). 490The memory isn't freed immediately with madvise(). It's freed in memory 491pressure if the memory is clean. Please note that the printed value might 492be lower than the real value due to optimizations used in the current 493implementation. If this is not desirable please file a bug report. 494 495"AnonHugePages" shows the ammount of memory backed by transparent hugepage. 496 497"ShmemPmdMapped" shows the ammount of shared (shmem/tmpfs) memory backed by 498huge pages. 499 500"Shared_Hugetlb" and "Private_Hugetlb" show the ammounts of memory backed by 501hugetlbfs page which is *not* counted in "RSS" or "PSS" field for historical 502reasons. And these are not included in {Shared,Private}_{Clean,Dirty} field. 503 504"Swap" shows how much would-be-anonymous memory is also used, but out on swap. 505 506For shmem mappings, "Swap" includes also the size of the mapped (and not 507replaced by copy-on-write) part of the underlying shmem object out on swap. 508"SwapPss" shows proportional swap share of this mapping. Unlike "Swap", this 509does not take into account swapped out page of underlying shmem objects. 510"Locked" indicates whether the mapping is locked in memory or not. 511"THPeligible" indicates whether the mapping is eligible for allocating THP 512pages - 1 if true, 0 otherwise. It just shows the current status. 513 514"VmFlags" field deserves a separate description. This member represents the 515kernel flags associated with the particular virtual memory area in two letter 516encoded manner. The codes are the following: 517 518 == ======================================= 519 rd readable 520 wr writeable 521 ex executable 522 sh shared 523 mr may read 524 mw may write 525 me may execute 526 ms may share 527 gd stack segment growns down 528 pf pure PFN range 529 dw disabled write to the mapped file 530 lo pages are locked in memory 531 io memory mapped I/O area 532 sr sequential read advise provided 533 rr random read advise provided 534 dc do not copy area on fork 535 de do not expand area on remapping 536 ac area is accountable 537 nr swap space is not reserved for the area 538 ht area uses huge tlb pages 539 ar architecture specific flag 540 dd do not include area into core dump 541 sd soft dirty flag 542 mm mixed map area 543 hg huge page advise flag 544 nh no huge page advise flag 545 mg mergable advise flag 546 == ======================================= 547 548Note that there is no guarantee that every flag and associated mnemonic will 549be present in all further kernel releases. Things get changed, the flags may 550be vanished or the reverse -- new added. Interpretation of their meaning 551might change in future as well. So each consumer of these flags has to 552follow each specific kernel version for the exact semantic. 553 554This file is only present if the CONFIG_MMU kernel configuration option is 555enabled. 556 557Note: reading /proc/PID/maps or /proc/PID/smaps is inherently racy (consistent 558output can be achieved only in the single read call). 559 560This typically manifests when doing partial reads of these files while the 561memory map is being modified. Despite the races, we do provide the following 562guarantees: 563 5641) The mapped addresses never go backwards, which implies no two 565 regions will ever overlap. 5662) If there is something at a given vaddr during the entirety of the 567 life of the smaps/maps walk, there will be some output for it. 568 569The /proc/PID/smaps_rollup file includes the same fields as /proc/PID/smaps, 570but their values are the sums of the corresponding values for all mappings of 571the process. Additionally, it contains these fields: 572 573- Pss_Anon 574- Pss_File 575- Pss_Shmem 576 577They represent the proportional shares of anonymous, file, and shmem pages, as 578described for smaps above. These fields are omitted in smaps since each 579mapping identifies the type (anon, file, or shmem) of all pages it contains. 580Thus all information in smaps_rollup can be derived from smaps, but at a 581significantly higher cost. 582 583The /proc/PID/clear_refs is used to reset the PG_Referenced and ACCESSED/YOUNG 584bits on both physical and virtual pages associated with a process, and the 585soft-dirty bit on pte (see Documentation/admin-guide/mm/soft-dirty.rst 586for details). 587To clear the bits for all the pages associated with the process:: 588 589 > echo 1 > /proc/PID/clear_refs 590 591To clear the bits for the anonymous pages associated with the process:: 592 593 > echo 2 > /proc/PID/clear_refs 594 595To clear the bits for the file mapped pages associated with the process:: 596 597 > echo 3 > /proc/PID/clear_refs 598 599To clear the soft-dirty bit:: 600 601 > echo 4 > /proc/PID/clear_refs 602 603To reset the peak resident set size ("high water mark") to the process's 604current value:: 605 606 > echo 5 > /proc/PID/clear_refs 607 608Any other value written to /proc/PID/clear_refs will have no effect. 609 610The /proc/pid/pagemap gives the PFN, which can be used to find the pageflags 611using /proc/kpageflags and number of times a page is mapped using 612/proc/kpagecount. For detailed explanation, see 613Documentation/admin-guide/mm/pagemap.rst. 614 615The /proc/pid/numa_maps is an extension based on maps, showing the memory 616locality and binding policy, as well as the memory usage (in pages) of 617each mapping. The output follows a general format where mapping details get 618summarized separated by blank spaces, one mapping per each file line:: 619 620 address policy mapping details 621 622 00400000 default file=/usr/local/bin/app mapped=1 active=0 N3=1 kernelpagesize_kB=4 623 00600000 default file=/usr/local/bin/app anon=1 dirty=1 N3=1 kernelpagesize_kB=4 624 3206000000 default file=/lib64/ld-2.12.so mapped=26 mapmax=6 N0=24 N3=2 kernelpagesize_kB=4 625 320621f000 default file=/lib64/ld-2.12.so anon=1 dirty=1 N3=1 kernelpagesize_kB=4 626 3206220000 default file=/lib64/ld-2.12.so anon=1 dirty=1 N3=1 kernelpagesize_kB=4 627 3206221000 default anon=1 dirty=1 N3=1 kernelpagesize_kB=4 628 3206800000 default file=/lib64/libc-2.12.so mapped=59 mapmax=21 active=55 N0=41 N3=18 kernelpagesize_kB=4 629 320698b000 default file=/lib64/libc-2.12.so 630 3206b8a000 default file=/lib64/libc-2.12.so anon=2 dirty=2 N3=2 kernelpagesize_kB=4 631 3206b8e000 default file=/lib64/libc-2.12.so anon=1 dirty=1 N3=1 kernelpagesize_kB=4 632 3206b8f000 default anon=3 dirty=3 active=1 N3=3 kernelpagesize_kB=4 633 7f4dc10a2000 default anon=3 dirty=3 N3=3 kernelpagesize_kB=4 634 7f4dc10b4000 default anon=2 dirty=2 active=1 N3=2 kernelpagesize_kB=4 635 7f4dc1200000 default file=/anon_hugepage\040(deleted) huge anon=1 dirty=1 N3=1 kernelpagesize_kB=2048 636 7fff335f0000 default stack anon=3 dirty=3 N3=3 kernelpagesize_kB=4 637 7fff3369d000 default mapped=1 mapmax=35 active=0 N3=1 kernelpagesize_kB=4 638 639Where: 640 641"address" is the starting address for the mapping; 642 643"policy" reports the NUMA memory policy set for the mapping (see Documentation/admin-guide/mm/numa_memory_policy.rst); 644 645"mapping details" summarizes mapping data such as mapping type, page usage counters, 646node locality page counters (N0 == node0, N1 == node1, ...) and the kernel page 647size, in KB, that is backing the mapping up. 648 6491.2 Kernel data 650--------------- 651 652Similar to the process entries, the kernel data files give information about 653the running kernel. The files used to obtain this information are contained in 654/proc and are listed in Table 1-5. Not all of these will be present in your 655system. It depends on the kernel configuration and the loaded modules, which 656files are there, and which are missing. 657 658.. table:: Table 1-5: Kernel info in /proc 659 660 ============ =============================================================== 661 File Content 662 ============ =============================================================== 663 apm Advanced power management info 664 buddyinfo Kernel memory allocator information (see text) (2.5) 665 bus Directory containing bus specific information 666 cmdline Kernel command line 667 cpuinfo Info about the CPU 668 devices Available devices (block and character) 669 dma Used DMS channels 670 filesystems Supported filesystems 671 driver Various drivers grouped here, currently rtc (2.4) 672 execdomains Execdomains, related to security (2.4) 673 fb Frame Buffer devices (2.4) 674 fs File system parameters, currently nfs/exports (2.4) 675 ide Directory containing info about the IDE subsystem 676 interrupts Interrupt usage 677 iomem Memory map (2.4) 678 ioports I/O port usage 679 irq Masks for irq to cpu affinity (2.4)(smp?) 680 isapnp ISA PnP (Plug&Play) Info (2.4) 681 kcore Kernel core image (can be ELF or A.OUT(deprecated in 2.4)) 682 kmsg Kernel messages 683 ksyms Kernel symbol table 684 loadavg Load average of last 1, 5 & 15 minutes 685 locks Kernel locks 686 meminfo Memory info 687 misc Miscellaneous 688 modules List of loaded modules 689 mounts Mounted filesystems 690 net Networking info (see text) 691 pagetypeinfo Additional page allocator information (see text) (2.5) 692 partitions Table of partitions known to the system 693 pci Deprecated info of PCI bus (new way -> /proc/bus/pci/, 694 decoupled by lspci (2.4) 695 rtc Real time clock 696 scsi SCSI info (see text) 697 slabinfo Slab pool info 698 softirqs softirq usage 699 stat Overall statistics 700 swaps Swap space utilization 701 sys See chapter 2 702 sysvipc Info of SysVIPC Resources (msg, sem, shm) (2.4) 703 tty Info of tty drivers 704 uptime Wall clock since boot, combined idle time of all cpus 705 version Kernel version 706 video bttv info of video resources (2.4) 707 vmallocinfo Show vmalloced areas 708 ============ =============================================================== 709 710You can, for example, check which interrupts are currently in use and what 711they are used for by looking in the file /proc/interrupts:: 712 713 > cat /proc/interrupts 714 CPU0 715 0: 8728810 XT-PIC timer 716 1: 895 XT-PIC keyboard 717 2: 0 XT-PIC cascade 718 3: 531695 XT-PIC aha152x 719 4: 2014133 XT-PIC serial 720 5: 44401 XT-PIC pcnet_cs 721 8: 2 XT-PIC rtc 722 11: 8 XT-PIC i82365 723 12: 182918 XT-PIC PS/2 Mouse 724 13: 1 XT-PIC fpu 725 14: 1232265 XT-PIC ide0 726 15: 7 XT-PIC ide1 727 NMI: 0 728 729In 2.4.* a couple of lines where added to this file LOC & ERR (this time is the 730output of a SMP machine):: 731 732 > cat /proc/interrupts 733 734 CPU0 CPU1 735 0: 1243498 1214548 IO-APIC-edge timer 736 1: 8949 8958 IO-APIC-edge keyboard 737 2: 0 0 XT-PIC cascade 738 5: 11286 10161 IO-APIC-edge soundblaster 739 8: 1 0 IO-APIC-edge rtc 740 9: 27422 27407 IO-APIC-edge 3c503 741 12: 113645 113873 IO-APIC-edge PS/2 Mouse 742 13: 0 0 XT-PIC fpu 743 14: 22491 24012 IO-APIC-edge ide0 744 15: 2183 2415 IO-APIC-edge ide1 745 17: 30564 30414 IO-APIC-level eth0 746 18: 177 164 IO-APIC-level bttv 747 NMI: 2457961 2457959 748 LOC: 2457882 2457881 749 ERR: 2155 750 751NMI is incremented in this case because every timer interrupt generates a NMI 752(Non Maskable Interrupt) which is used by the NMI Watchdog to detect lockups. 753 754LOC is the local interrupt counter of the internal APIC of every CPU. 755 756ERR is incremented in the case of errors in the IO-APIC bus (the bus that 757connects the CPUs in a SMP system. This means that an error has been detected, 758the IO-APIC automatically retry the transmission, so it should not be a big 759problem, but you should read the SMP-FAQ. 760 761In 2.6.2* /proc/interrupts was expanded again. This time the goal was for 762/proc/interrupts to display every IRQ vector in use by the system, not 763just those considered 'most important'. The new vectors are: 764 765THR 766 interrupt raised when a machine check threshold counter 767 (typically counting ECC corrected errors of memory or cache) exceeds 768 a configurable threshold. Only available on some systems. 769 770TRM 771 a thermal event interrupt occurs when a temperature threshold 772 has been exceeded for the CPU. This interrupt may also be generated 773 when the temperature drops back to normal. 774 775SPU 776 a spurious interrupt is some interrupt that was raised then lowered 777 by some IO device before it could be fully processed by the APIC. Hence 778 the APIC sees the interrupt but does not know what device it came from. 779 For this case the APIC will generate the interrupt with a IRQ vector 780 of 0xff. This might also be generated by chipset bugs. 781 782RES, CAL, TLB] 783 rescheduling, call and TLB flush interrupts are 784 sent from one CPU to another per the needs of the OS. Typically, 785 their statistics are used by kernel developers and interested users to 786 determine the occurrence of interrupts of the given type. 787 788The above IRQ vectors are displayed only when relevant. For example, 789the threshold vector does not exist on x86_64 platforms. Others are 790suppressed when the system is a uniprocessor. As of this writing, only 791i386 and x86_64 platforms support the new IRQ vector displays. 792 793Of some interest is the introduction of the /proc/irq directory to 2.4. 794It could be used to set IRQ to CPU affinity, this means that you can "hook" an 795IRQ to only one CPU, or to exclude a CPU of handling IRQs. The contents of the 796irq subdir is one subdir for each IRQ, and two files; default_smp_affinity and 797prof_cpu_mask. 798 799For example:: 800 801 > ls /proc/irq/ 802 0 10 12 14 16 18 2 4 6 8 prof_cpu_mask 803 1 11 13 15 17 19 3 5 7 9 default_smp_affinity 804 > ls /proc/irq/0/ 805 smp_affinity 806 807smp_affinity is a bitmask, in which you can specify which CPUs can handle the 808IRQ, you can set it by doing:: 809 810 > echo 1 > /proc/irq/10/smp_affinity 811 812This means that only the first CPU will handle the IRQ, but you can also echo 8135 which means that only the first and third CPU can handle the IRQ. 814 815The contents of each smp_affinity file is the same by default:: 816 817 > cat /proc/irq/0/smp_affinity 818 ffffffff 819 820There is an alternate interface, smp_affinity_list which allows specifying 821a cpu range instead of a bitmask:: 822 823 > cat /proc/irq/0/smp_affinity_list 824 1024-1031 825 826The default_smp_affinity mask applies to all non-active IRQs, which are the 827IRQs which have not yet been allocated/activated, and hence which lack a 828/proc/irq/[0-9]* directory. 829 830The node file on an SMP system shows the node to which the device using the IRQ 831reports itself as being attached. This hardware locality information does not 832include information about any possible driver locality preference. 833 834prof_cpu_mask specifies which CPUs are to be profiled by the system wide 835profiler. Default value is ffffffff (all cpus if there are only 32 of them). 836 837The way IRQs are routed is handled by the IO-APIC, and it's Round Robin 838between all the CPUs which are allowed to handle it. As usual the kernel has 839more info than you and does a better job than you, so the defaults are the 840best choice for almost everyone. [Note this applies only to those IO-APIC's 841that support "Round Robin" interrupt distribution.] 842 843There are three more important subdirectories in /proc: net, scsi, and sys. 844The general rule is that the contents, or even the existence of these 845directories, depend on your kernel configuration. If SCSI is not enabled, the 846directory scsi may not exist. The same is true with the net, which is there 847only when networking support is present in the running kernel. 848 849The slabinfo file gives information about memory usage at the slab level. 850Linux uses slab pools for memory management above page level in version 2.2. 851Commonly used objects have their own slab pool (such as network buffers, 852directory cache, and so on). 853 854:: 855 856 > cat /proc/buddyinfo 857 858 Node 0, zone DMA 0 4 5 4 4 3 ... 859 Node 0, zone Normal 1 0 0 1 101 8 ... 860 Node 0, zone HighMem 2 0 0 1 1 0 ... 861 862External fragmentation is a problem under some workloads, and buddyinfo is a 863useful tool for helping diagnose these problems. Buddyinfo will give you a 864clue as to how big an area you can safely allocate, or why a previous 865allocation failed. 866 867Each column represents the number of pages of a certain order which are 868available. In this case, there are 0 chunks of 2^0*PAGE_SIZE available in 869ZONE_DMA, 4 chunks of 2^1*PAGE_SIZE in ZONE_DMA, 101 chunks of 2^4*PAGE_SIZE 870available in ZONE_NORMAL, etc... 871 872More information relevant to external fragmentation can be found in 873pagetypeinfo:: 874 875 > cat /proc/pagetypeinfo 876 Page block order: 9 877 Pages per block: 512 878 879 Free pages count per migrate type at order 0 1 2 3 4 5 6 7 8 9 10 880 Node 0, zone DMA, type Unmovable 0 0 0 1 1 1 1 1 1 1 0 881 Node 0, zone DMA, type Reclaimable 0 0 0 0 0 0 0 0 0 0 0 882 Node 0, zone DMA, type Movable 1 1 2 1 2 1 1 0 1 0 2 883 Node 0, zone DMA, type Reserve 0 0 0 0 0 0 0 0 0 1 0 884 Node 0, zone DMA, type Isolate 0 0 0 0 0 0 0 0 0 0 0 885 Node 0, zone DMA32, type Unmovable 103 54 77 1 1 1 11 8 7 1 9 886 Node 0, zone DMA32, type Reclaimable 0 0 2 1 0 0 0 0 1 0 0 887 Node 0, zone DMA32, type Movable 169 152 113 91 77 54 39 13 6 1 452 888 Node 0, zone DMA32, type Reserve 1 2 2 2 2 0 1 1 1 1 0 889 Node 0, zone DMA32, type Isolate 0 0 0 0 0 0 0 0 0 0 0 890 891 Number of blocks type Unmovable Reclaimable Movable Reserve Isolate 892 Node 0, zone DMA 2 0 5 1 0 893 Node 0, zone DMA32 41 6 967 2 0 894 895Fragmentation avoidance in the kernel works by grouping pages of different 896migrate types into the same contiguous regions of memory called page blocks. 897A page block is typically the size of the default hugepage size e.g. 2MB on 898X86-64. By keeping pages grouped based on their ability to move, the kernel 899can reclaim pages within a page block to satisfy a high-order allocation. 900 901The pagetypinfo begins with information on the size of a page block. It 902then gives the same type of information as buddyinfo except broken down 903by migrate-type and finishes with details on how many page blocks of each 904type exist. 905 906If min_free_kbytes has been tuned correctly (recommendations made by hugeadm 907from libhugetlbfs https://github.com/libhugetlbfs/libhugetlbfs/), one can 908make an estimate of the likely number of huge pages that can be allocated 909at a given point in time. All the "Movable" blocks should be allocatable 910unless memory has been mlock()'d. Some of the Reclaimable blocks should 911also be allocatable although a lot of filesystem metadata may have to be 912reclaimed to achieve this. 913 914 915meminfo 916~~~~~~~ 917 918Provides information about distribution and utilization of memory. This 919varies by architecture and compile options. The following is from a 92016GB PIII, which has highmem enabled. You may not have all of these fields. 921 922:: 923 924 > cat /proc/meminfo 925 926 MemTotal: 16344972 kB 927 MemFree: 13634064 kB 928 MemAvailable: 14836172 kB 929 Buffers: 3656 kB 930 Cached: 1195708 kB 931 SwapCached: 0 kB 932 Active: 891636 kB 933 Inactive: 1077224 kB 934 HighTotal: 15597528 kB 935 HighFree: 13629632 kB 936 LowTotal: 747444 kB 937 LowFree: 4432 kB 938 SwapTotal: 0 kB 939 SwapFree: 0 kB 940 Dirty: 968 kB 941 Writeback: 0 kB 942 AnonPages: 861800 kB 943 Mapped: 280372 kB 944 Shmem: 644 kB 945 KReclaimable: 168048 kB 946 Slab: 284364 kB 947 SReclaimable: 159856 kB 948 SUnreclaim: 124508 kB 949 PageTables: 24448 kB 950 NFS_Unstable: 0 kB 951 Bounce: 0 kB 952 WritebackTmp: 0 kB 953 CommitLimit: 7669796 kB 954 Committed_AS: 100056 kB 955 VmallocTotal: 112216 kB 956 VmallocUsed: 428 kB 957 VmallocChunk: 111088 kB 958 Percpu: 62080 kB 959 HardwareCorrupted: 0 kB 960 AnonHugePages: 49152 kB 961 ShmemHugePages: 0 kB 962 ShmemPmdMapped: 0 kB 963 964MemTotal 965 Total usable ram (i.e. physical ram minus a few reserved 966 bits and the kernel binary code) 967MemFree 968 The sum of LowFree+HighFree 969MemAvailable 970 An estimate of how much memory is available for starting new 971 applications, without swapping. Calculated from MemFree, 972 SReclaimable, the size of the file LRU lists, and the low 973 watermarks in each zone. 974 The estimate takes into account that the system needs some 975 page cache to function well, and that not all reclaimable 976 slab will be reclaimable, due to items being in use. The 977 impact of those factors will vary from system to system. 978Buffers 979 Relatively temporary storage for raw disk blocks 980 shouldn't get tremendously large (20MB or so) 981Cached 982 in-memory cache for files read from the disk (the 983 pagecache). Doesn't include SwapCached 984SwapCached 985 Memory that once was swapped out, is swapped back in but 986 still also is in the swapfile (if memory is needed it 987 doesn't need to be swapped out AGAIN because it is already 988 in the swapfile. This saves I/O) 989Active 990 Memory that has been used more recently and usually not 991 reclaimed unless absolutely necessary. 992Inactive 993 Memory which has been less recently used. It is more 994 eligible to be reclaimed for other purposes 995HighTotal, HighFree 996 Highmem is all memory above ~860MB of physical memory 997 Highmem areas are for use by userspace programs, or 998 for the pagecache. The kernel must use tricks to access 999 this memory, making it slower to access than lowmem. 1000LowTotal, LowFree 1001 Lowmem is memory which can be used for everything that 1002 highmem can be used for, but it is also available for the 1003 kernel's use for its own data structures. Among many 1004 other things, it is where everything from the Slab is 1005 allocated. Bad things happen when you're out of lowmem. 1006SwapTotal 1007 total amount of swap space available 1008SwapFree 1009 Memory which has been evicted from RAM, and is temporarily 1010 on the disk 1011Dirty 1012 Memory which is waiting to get written back to the disk 1013Writeback 1014 Memory which is actively being written back to the disk 1015AnonPages 1016 Non-file backed pages mapped into userspace page tables 1017HardwareCorrupted 1018 The amount of RAM/memory in KB, the kernel identifies as 1019 corrupted. 1020AnonHugePages 1021 Non-file backed huge pages mapped into userspace page tables 1022Mapped 1023 files which have been mmaped, such as libraries 1024Shmem 1025 Total memory used by shared memory (shmem) and tmpfs 1026ShmemHugePages 1027 Memory used by shared memory (shmem) and tmpfs allocated 1028 with huge pages 1029ShmemPmdMapped 1030 Shared memory mapped into userspace with huge pages 1031KReclaimable 1032 Kernel allocations that the kernel will attempt to reclaim 1033 under memory pressure. Includes SReclaimable (below), and other 1034 direct allocations with a shrinker. 1035Slab 1036 in-kernel data structures cache 1037SReclaimable 1038 Part of Slab, that might be reclaimed, such as caches 1039SUnreclaim 1040 Part of Slab, that cannot be reclaimed on memory pressure 1041PageTables 1042 amount of memory dedicated to the lowest level of page 1043 tables. 1044NFS_Unstable 1045 NFS pages sent to the server, but not yet committed to stable 1046 storage 1047Bounce 1048 Memory used for block device "bounce buffers" 1049WritebackTmp 1050 Memory used by FUSE for temporary writeback buffers 1051CommitLimit 1052 Based on the overcommit ratio ('vm.overcommit_ratio'), 1053 this is the total amount of memory currently available to 1054 be allocated on the system. This limit is only adhered to 1055 if strict overcommit accounting is enabled (mode 2 in 1056 'vm.overcommit_memory'). 1057 1058 The CommitLimit is calculated with the following formula:: 1059 1060 CommitLimit = ([total RAM pages] - [total huge TLB pages]) * 1061 overcommit_ratio / 100 + [total swap pages] 1062 1063 For example, on a system with 1G of physical RAM and 7G 1064 of swap with a `vm.overcommit_ratio` of 30 it would 1065 yield a CommitLimit of 7.3G. 1066 1067 For more details, see the memory overcommit documentation 1068 in vm/overcommit-accounting. 1069Committed_AS 1070 The amount of memory presently allocated on the system. 1071 The committed memory is a sum of all of the memory which 1072 has been allocated by processes, even if it has not been 1073 "used" by them as of yet. A process which malloc()'s 1G 1074 of memory, but only touches 300M of it will show up as 1075 using 1G. This 1G is memory which has been "committed" to 1076 by the VM and can be used at any time by the allocating 1077 application. With strict overcommit enabled on the system 1078 (mode 2 in 'vm.overcommit_memory'),allocations which would 1079 exceed the CommitLimit (detailed above) will not be permitted. 1080 This is useful if one needs to guarantee that processes will 1081 not fail due to lack of memory once that memory has been 1082 successfully allocated. 1083VmallocTotal 1084 total size of vmalloc memory area 1085VmallocUsed 1086 amount of vmalloc area which is used 1087VmallocChunk 1088 largest contiguous block of vmalloc area which is free 1089Percpu 1090 Memory allocated to the percpu allocator used to back percpu 1091 allocations. This stat excludes the cost of metadata. 1092 1093vmallocinfo 1094~~~~~~~~~~~ 1095 1096Provides information about vmalloced/vmaped areas. One line per area, 1097containing the virtual address range of the area, size in bytes, 1098caller information of the creator, and optional information depending 1099on the kind of area : 1100 1101 ========== =================================================== 1102 pages=nr number of pages 1103 phys=addr if a physical address was specified 1104 ioremap I/O mapping (ioremap() and friends) 1105 vmalloc vmalloc() area 1106 vmap vmap()ed pages 1107 user VM_USERMAP area 1108 vpages buffer for pages pointers was vmalloced (huge area) 1109 N<node>=nr (Only on NUMA kernels) 1110 Number of pages allocated on memory node <node> 1111 ========== =================================================== 1112 1113:: 1114 1115 > cat /proc/vmallocinfo 1116 0xffffc20000000000-0xffffc20000201000 2101248 alloc_large_system_hash+0x204 ... 1117 /0x2c0 pages=512 vmalloc N0=128 N1=128 N2=128 N3=128 1118 0xffffc20000201000-0xffffc20000302000 1052672 alloc_large_system_hash+0x204 ... 1119 /0x2c0 pages=256 vmalloc N0=64 N1=64 N2=64 N3=64 1120 0xffffc20000302000-0xffffc20000304000 8192 acpi_tb_verify_table+0x21/0x4f... 1121 phys=7fee8000 ioremap 1122 0xffffc20000304000-0xffffc20000307000 12288 acpi_tb_verify_table+0x21/0x4f... 1123 phys=7fee7000 ioremap 1124 0xffffc2000031d000-0xffffc2000031f000 8192 init_vdso_vars+0x112/0x210 1125 0xffffc2000031f000-0xffffc2000032b000 49152 cramfs_uncompress_init+0x2e ... 1126 /0x80 pages=11 vmalloc N0=3 N1=3 N2=2 N3=3 1127 0xffffc2000033a000-0xffffc2000033d000 12288 sys_swapon+0x640/0xac0 ... 1128 pages=2 vmalloc N1=2 1129 0xffffc20000347000-0xffffc2000034c000 20480 xt_alloc_table_info+0xfe ... 1130 /0x130 [x_tables] pages=4 vmalloc N0=4 1131 0xffffffffa0000000-0xffffffffa000f000 61440 sys_init_module+0xc27/0x1d00 ... 1132 pages=14 vmalloc N2=14 1133 0xffffffffa000f000-0xffffffffa0014000 20480 sys_init_module+0xc27/0x1d00 ... 1134 pages=4 vmalloc N1=4 1135 0xffffffffa0014000-0xffffffffa0017000 12288 sys_init_module+0xc27/0x1d00 ... 1136 pages=2 vmalloc N1=2 1137 0xffffffffa0017000-0xffffffffa0022000 45056 sys_init_module+0xc27/0x1d00 ... 1138 pages=10 vmalloc N0=10 1139 1140 1141softirqs 1142~~~~~~~~ 1143 1144Provides counts of softirq handlers serviced since boot time, for each cpu. 1145 1146:: 1147 1148 > cat /proc/softirqs 1149 CPU0 CPU1 CPU2 CPU3 1150 HI: 0 0 0 0 1151 TIMER: 27166 27120 27097 27034 1152 NET_TX: 0 0 0 17 1153 NET_RX: 42 0 0 39 1154 BLOCK: 0 0 107 1121 1155 TASKLET: 0 0 0 290 1156 SCHED: 27035 26983 26971 26746 1157 HRTIMER: 0 0 0 0 1158 RCU: 1678 1769 2178 2250 1159 1160 11611.3 IDE devices in /proc/ide 1162---------------------------- 1163 1164The subdirectory /proc/ide contains information about all IDE devices of which 1165the kernel is aware. There is one subdirectory for each IDE controller, the 1166file drivers and a link for each IDE device, pointing to the device directory 1167in the controller specific subtree. 1168 1169The file drivers contains general information about the drivers used for the 1170IDE devices:: 1171 1172 > cat /proc/ide/drivers 1173 ide-cdrom version 4.53 1174 ide-disk version 1.08 1175 1176More detailed information can be found in the controller specific 1177subdirectories. These are named ide0, ide1 and so on. Each of these 1178directories contains the files shown in table 1-6. 1179 1180 1181.. table:: Table 1-6: IDE controller info in /proc/ide/ide? 1182 1183 ======= ======================================= 1184 File Content 1185 ======= ======================================= 1186 channel IDE channel (0 or 1) 1187 config Configuration (only for PCI/IDE bridge) 1188 mate Mate name 1189 model Type/Chipset of IDE controller 1190 ======= ======================================= 1191 1192Each device connected to a controller has a separate subdirectory in the 1193controllers directory. The files listed in table 1-7 are contained in these 1194directories. 1195 1196 1197.. table:: Table 1-7: IDE device information 1198 1199 ================ ========================================== 1200 File Content 1201 ================ ========================================== 1202 cache The cache 1203 capacity Capacity of the medium (in 512Byte blocks) 1204 driver driver and version 1205 geometry physical and logical geometry 1206 identify device identify block 1207 media media type 1208 model device identifier 1209 settings device setup 1210 smart_thresholds IDE disk management thresholds 1211 smart_values IDE disk management values 1212 ================ ========================================== 1213 1214The most interesting file is ``settings``. This file contains a nice 1215overview of the drive parameters:: 1216 1217 # cat /proc/ide/ide0/hda/settings 1218 name value min max mode 1219 ---- ----- --- --- ---- 1220 bios_cyl 526 0 65535 rw 1221 bios_head 255 0 255 rw 1222 bios_sect 63 0 63 rw 1223 breada_readahead 4 0 127 rw 1224 bswap 0 0 1 r 1225 file_readahead 72 0 2097151 rw 1226 io_32bit 0 0 3 rw 1227 keepsettings 0 0 1 rw 1228 max_kb_per_request 122 1 127 rw 1229 multcount 0 0 8 rw 1230 nice1 1 0 1 rw 1231 nowerr 0 0 1 rw 1232 pio_mode write-only 0 255 w 1233 slow 0 0 1 rw 1234 unmaskirq 0 0 1 rw 1235 using_dma 0 0 1 rw 1236 1237 12381.4 Networking info in /proc/net 1239-------------------------------- 1240 1241The subdirectory /proc/net follows the usual pattern. Table 1-8 shows the 1242additional values you get for IP version 6 if you configure the kernel to 1243support this. Table 1-9 lists the files and their meaning. 1244 1245 1246.. table:: Table 1-8: IPv6 info in /proc/net 1247 1248 ========== ===================================================== 1249 File Content 1250 ========== ===================================================== 1251 udp6 UDP sockets (IPv6) 1252 tcp6 TCP sockets (IPv6) 1253 raw6 Raw device statistics (IPv6) 1254 igmp6 IP multicast addresses, which this host joined (IPv6) 1255 if_inet6 List of IPv6 interface addresses 1256 ipv6_route Kernel routing table for IPv6 1257 rt6_stats Global IPv6 routing tables statistics 1258 sockstat6 Socket statistics (IPv6) 1259 snmp6 Snmp data (IPv6) 1260 ========== ===================================================== 1261 1262.. table:: Table 1-9: Network info in /proc/net 1263 1264 ============= ================================================================ 1265 File Content 1266 ============= ================================================================ 1267 arp Kernel ARP table 1268 dev network devices with statistics 1269 dev_mcast the Layer2 multicast groups a device is listening too 1270 (interface index, label, number of references, number of bound 1271 addresses). 1272 dev_stat network device status 1273 ip_fwchains Firewall chain linkage 1274 ip_fwnames Firewall chain names 1275 ip_masq Directory containing the masquerading tables 1276 ip_masquerade Major masquerading table 1277 netstat Network statistics 1278 raw raw device statistics 1279 route Kernel routing table 1280 rpc Directory containing rpc info 1281 rt_cache Routing cache 1282 snmp SNMP data 1283 sockstat Socket statistics 1284 tcp TCP sockets 1285 udp UDP sockets 1286 unix UNIX domain sockets 1287 wireless Wireless interface data (Wavelan etc) 1288 igmp IP multicast addresses, which this host joined 1289 psched Global packet scheduler parameters. 1290 netlink List of PF_NETLINK sockets 1291 ip_mr_vifs List of multicast virtual interfaces 1292 ip_mr_cache List of multicast routing cache 1293 ============= ================================================================ 1294 1295You can use this information to see which network devices are available in 1296your system and how much traffic was routed over those devices:: 1297 1298 > cat /proc/net/dev 1299 Inter-|Receive |[... 1300 face |bytes packets errs drop fifo frame compressed multicast|[... 1301 lo: 908188 5596 0 0 0 0 0 0 [... 1302 ppp0:15475140 20721 410 0 0 410 0 0 [... 1303 eth0: 614530 7085 0 0 0 0 0 1 [... 1304 1305 ...] Transmit 1306 ...] bytes packets errs drop fifo colls carrier compressed 1307 ...] 908188 5596 0 0 0 0 0 0 1308 ...] 1375103 17405 0 0 0 0 0 0 1309 ...] 1703981 5535 0 0 0 3 0 0 1310 1311In addition, each Channel Bond interface has its own directory. For 1312example, the bond0 device will have a directory called /proc/net/bond0/. 1313It will contain information that is specific to that bond, such as the 1314current slaves of the bond, the link status of the slaves, and how 1315many times the slaves link has failed. 1316 13171.5 SCSI info 1318------------- 1319 1320If you have a SCSI host adapter in your system, you'll find a subdirectory 1321named after the driver for this adapter in /proc/scsi. You'll also see a list 1322of all recognized SCSI devices in /proc/scsi:: 1323 1324 >cat /proc/scsi/scsi 1325 Attached devices: 1326 Host: scsi0 Channel: 00 Id: 00 Lun: 00 1327 Vendor: IBM Model: DGHS09U Rev: 03E0 1328 Type: Direct-Access ANSI SCSI revision: 03 1329 Host: scsi0 Channel: 00 Id: 06 Lun: 00 1330 Vendor: PIONEER Model: CD-ROM DR-U06S Rev: 1.04 1331 Type: CD-ROM ANSI SCSI revision: 02 1332 1333 1334The directory named after the driver has one file for each adapter found in 1335the system. These files contain information about the controller, including 1336the used IRQ and the IO address range. The amount of information shown is 1337dependent on the adapter you use. The example shows the output for an Adaptec 1338AHA-2940 SCSI adapter:: 1339 1340 > cat /proc/scsi/aic7xxx/0 1341 1342 Adaptec AIC7xxx driver version: 5.1.19/3.2.4 1343 Compile Options: 1344 TCQ Enabled By Default : Disabled 1345 AIC7XXX_PROC_STATS : Disabled 1346 AIC7XXX_RESET_DELAY : 5 1347 Adapter Configuration: 1348 SCSI Adapter: Adaptec AHA-294X Ultra SCSI host adapter 1349 Ultra Wide Controller 1350 PCI MMAPed I/O Base: 0xeb001000 1351 Adapter SEEPROM Config: SEEPROM found and used. 1352 Adaptec SCSI BIOS: Enabled 1353 IRQ: 10 1354 SCBs: Active 0, Max Active 2, 1355 Allocated 15, HW 16, Page 255 1356 Interrupts: 160328 1357 BIOS Control Word: 0x18b6 1358 Adapter Control Word: 0x005b 1359 Extended Translation: Enabled 1360 Disconnect Enable Flags: 0xffff 1361 Ultra Enable Flags: 0x0001 1362 Tag Queue Enable Flags: 0x0000 1363 Ordered Queue Tag Flags: 0x0000 1364 Default Tag Queue Depth: 8 1365 Tagged Queue By Device array for aic7xxx host instance 0: 1366 {255,255,255,255,255,255,255,255,255,255,255,255,255,255,255,255} 1367 Actual queue depth per device for aic7xxx host instance 0: 1368 {1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1} 1369 Statistics: 1370 (scsi0:0:0:0) 1371 Device using Wide/Sync transfers at 40.0 MByte/sec, offset 8 1372 Transinfo settings: current(12/8/1/0), goal(12/8/1/0), user(12/15/1/0) 1373 Total transfers 160151 (74577 reads and 85574 writes) 1374 (scsi0:0:6:0) 1375 Device using Narrow/Sync transfers at 5.0 MByte/sec, offset 15 1376 Transinfo settings: current(50/15/0/0), goal(50/15/0/0), user(50/15/0/0) 1377 Total transfers 0 (0 reads and 0 writes) 1378 1379 13801.6 Parallel port info in /proc/parport 1381--------------------------------------- 1382 1383The directory /proc/parport contains information about the parallel ports of 1384your system. It has one subdirectory for each port, named after the port 1385number (0,1,2,...). 1386 1387These directories contain the four files shown in Table 1-10. 1388 1389 1390.. table:: Table 1-10: Files in /proc/parport 1391 1392 ========= ==================================================================== 1393 File Content 1394 ========= ==================================================================== 1395 autoprobe Any IEEE-1284 device ID information that has been acquired. 1396 devices list of the device drivers using that port. A + will appear by the 1397 name of the device currently using the port (it might not appear 1398 against any). 1399 hardware Parallel port's base address, IRQ line and DMA channel. 1400 irq IRQ that parport is using for that port. This is in a separate 1401 file to allow you to alter it by writing a new value in (IRQ 1402 number or none). 1403 ========= ==================================================================== 1404 14051.7 TTY info in /proc/tty 1406------------------------- 1407 1408Information about the available and actually used tty's can be found in the 1409directory /proc/tty.You'll find entries for drivers and line disciplines in 1410this directory, as shown in Table 1-11. 1411 1412 1413.. table:: Table 1-11: Files in /proc/tty 1414 1415 ============= ============================================== 1416 File Content 1417 ============= ============================================== 1418 drivers list of drivers and their usage 1419 ldiscs registered line disciplines 1420 driver/serial usage statistic and status of single tty lines 1421 ============= ============================================== 1422 1423To see which tty's are currently in use, you can simply look into the file 1424/proc/tty/drivers:: 1425 1426 > cat /proc/tty/drivers 1427 pty_slave /dev/pts 136 0-255 pty:slave 1428 pty_master /dev/ptm 128 0-255 pty:master 1429 pty_slave /dev/ttyp 3 0-255 pty:slave 1430 pty_master /dev/pty 2 0-255 pty:master 1431 serial /dev/cua 5 64-67 serial:callout 1432 serial /dev/ttyS 4 64-67 serial 1433 /dev/tty0 /dev/tty0 4 0 system:vtmaster 1434 /dev/ptmx /dev/ptmx 5 2 system 1435 /dev/console /dev/console 5 1 system:console 1436 /dev/tty /dev/tty 5 0 system:/dev/tty 1437 unknown /dev/tty 4 1-63 console 1438 1439 14401.8 Miscellaneous kernel statistics in /proc/stat 1441------------------------------------------------- 1442 1443Various pieces of information about kernel activity are available in the 1444/proc/stat file. All of the numbers reported in this file are aggregates 1445since the system first booted. For a quick look, simply cat the file:: 1446 1447 > cat /proc/stat 1448 cpu 2255 34 2290 22625563 6290 127 456 0 0 0 1449 cpu0 1132 34 1441 11311718 3675 127 438 0 0 0 1450 cpu1 1123 0 849 11313845 2614 0 18 0 0 0 1451 intr 114930548 113199788 3 0 5 263 0 4 [... lots more numbers ...] 1452 ctxt 1990473 1453 btime 1062191376 1454 processes 2915 1455 procs_running 1 1456 procs_blocked 0 1457 softirq 183433 0 21755 12 39 1137 231 21459 2263 1458 1459The very first "cpu" line aggregates the numbers in all of the other "cpuN" 1460lines. These numbers identify the amount of time the CPU has spent performing 1461different kinds of work. Time units are in USER_HZ (typically hundredths of a 1462second). The meanings of the columns are as follows, from left to right: 1463 1464- user: normal processes executing in user mode 1465- nice: niced processes executing in user mode 1466- system: processes executing in kernel mode 1467- idle: twiddling thumbs 1468- iowait: In a word, iowait stands for waiting for I/O to complete. But there 1469 are several problems: 1470 1471 1. Cpu will not wait for I/O to complete, iowait is the time that a task is 1472 waiting for I/O to complete. When cpu goes into idle state for 1473 outstanding task io, another task will be scheduled on this CPU. 1474 2. In a multi-core CPU, the task waiting for I/O to complete is not running 1475 on any CPU, so the iowait of each CPU is difficult to calculate. 1476 3. The value of iowait field in /proc/stat will decrease in certain 1477 conditions. 1478 1479 So, the iowait is not reliable by reading from /proc/stat. 1480- irq: servicing interrupts 1481- softirq: servicing softirqs 1482- steal: involuntary wait 1483- guest: running a normal guest 1484- guest_nice: running a niced guest 1485 1486The "intr" line gives counts of interrupts serviced since boot time, for each 1487of the possible system interrupts. The first column is the total of all 1488interrupts serviced including unnumbered architecture specific interrupts; 1489each subsequent column is the total for that particular numbered interrupt. 1490Unnumbered interrupts are not shown, only summed into the total. 1491 1492The "ctxt" line gives the total number of context switches across all CPUs. 1493 1494The "btime" line gives the time at which the system booted, in seconds since 1495the Unix epoch. 1496 1497The "processes" line gives the number of processes and threads created, which 1498includes (but is not limited to) those created by calls to the fork() and 1499clone() system calls. 1500 1501The "procs_running" line gives the total number of threads that are 1502running or ready to run (i.e., the total number of runnable threads). 1503 1504The "procs_blocked" line gives the number of processes currently blocked, 1505waiting for I/O to complete. 1506 1507The "softirq" line gives counts of softirqs serviced since boot time, for each 1508of the possible system softirqs. The first column is the total of all 1509softirqs serviced; each subsequent column is the total for that particular 1510softirq. 1511 1512 15131.9 Ext4 file system parameters 1514------------------------------- 1515 1516Information about mounted ext4 file systems can be found in 1517/proc/fs/ext4. Each mounted filesystem will have a directory in 1518/proc/fs/ext4 based on its device name (i.e., /proc/fs/ext4/hdc or 1519/proc/fs/ext4/dm-0). The files in each per-device directory are shown 1520in Table 1-12, below. 1521 1522.. table:: Table 1-12: Files in /proc/fs/ext4/<devname> 1523 1524 ============== ========================================================== 1525 File Content 1526 mb_groups details of multiblock allocator buddy cache of free blocks 1527 ============== ========================================================== 1528 15292.0 /proc/consoles 1530------------------ 1531Shows registered system console lines. 1532 1533To see which character device lines are currently used for the system console 1534/dev/console, you may simply look into the file /proc/consoles:: 1535 1536 > cat /proc/consoles 1537 tty0 -WU (ECp) 4:7 1538 ttyS0 -W- (Ep) 4:64 1539 1540The columns are: 1541 1542+--------------------+-------------------------------------------------------+ 1543| device | name of the device | 1544+====================+=======================================================+ 1545| operations | * R = can do read operations | 1546| | * W = can do write operations | 1547| | * U = can do unblank | 1548+--------------------+-------------------------------------------------------+ 1549| flags | * E = it is enabled | 1550| | * C = it is preferred console | 1551| | * B = it is primary boot console | 1552| | * p = it is used for printk buffer | 1553| | * b = it is not a TTY but a Braille device | 1554| | * a = it is safe to use when cpu is offline | 1555+--------------------+-------------------------------------------------------+ 1556| major:minor | major and minor number of the device separated by a | 1557| | colon | 1558+--------------------+-------------------------------------------------------+ 1559 1560Summary 1561------- 1562 1563The /proc file system serves information about the running system. It not only 1564allows access to process data but also allows you to request the kernel status 1565by reading files in the hierarchy. 1566 1567The directory structure of /proc reflects the types of information and makes 1568it easy, if not obvious, where to look for specific data. 1569 1570Chapter 2: Modifying System Parameters 1571====================================== 1572 1573In This Chapter 1574--------------- 1575 1576* Modifying kernel parameters by writing into files found in /proc/sys 1577* Exploring the files which modify certain parameters 1578* Review of the /proc/sys file tree 1579 1580------------------------------------------------------------------------------ 1581 1582A very interesting part of /proc is the directory /proc/sys. This is not only 1583a source of information, it also allows you to change parameters within the 1584kernel. Be very careful when attempting this. You can optimize your system, 1585but you can also cause it to crash. Never alter kernel parameters on a 1586production system. Set up a development machine and test to make sure that 1587everything works the way you want it to. You may have no alternative but to 1588reboot the machine once an error has been made. 1589 1590To change a value, simply echo the new value into the file. An example is 1591given below in the section on the file system data. You need to be root to do 1592this. You can create your own boot script to perform this every time your 1593system boots. 1594 1595The files in /proc/sys can be used to fine tune and monitor miscellaneous and 1596general things in the operation of the Linux kernel. Since some of the files 1597can inadvertently disrupt your system, it is advisable to read both 1598documentation and source before actually making adjustments. In any case, be 1599very careful when writing to any of these files. The entries in /proc may 1600change slightly between the 2.1.* and the 2.2 kernel, so if there is any doubt 1601review the kernel documentation in the directory /usr/src/linux/Documentation. 1602This chapter is heavily based on the documentation included in the pre 2.2 1603kernels, and became part of it in version 2.2.1 of the Linux kernel. 1604 1605Please see: Documentation/admin-guide/sysctl/ directory for descriptions of these 1606entries. 1607 1608Summary 1609------- 1610 1611Certain aspects of kernel behavior can be modified at runtime, without the 1612need to recompile the kernel, or even to reboot the system. The files in the 1613/proc/sys tree can not only be read, but also modified. You can use the echo 1614command to write value into these files, thereby changing the default settings 1615of the kernel. 1616 1617 1618Chapter 3: Per-process Parameters 1619================================= 1620 16213.1 /proc/<pid>/oom_adj & /proc/<pid>/oom_score_adj- Adjust the oom-killer score 1622-------------------------------------------------------------------------------- 1623 1624These file can be used to adjust the badness heuristic used to select which 1625process gets killed in out of memory conditions. 1626 1627The badness heuristic assigns a value to each candidate task ranging from 0 1628(never kill) to 1000 (always kill) to determine which process is targeted. The 1629units are roughly a proportion along that range of allowed memory the process 1630may allocate from based on an estimation of its current memory and swap use. 1631For example, if a task is using all allowed memory, its badness score will be 16321000. If it is using half of its allowed memory, its score will be 500. 1633 1634There is an additional factor included in the badness score: the current memory 1635and swap usage is discounted by 3% for root processes. 1636 1637The amount of "allowed" memory depends on the context in which the oom killer 1638was called. If it is due to the memory assigned to the allocating task's cpuset 1639being exhausted, the allowed memory represents the set of mems assigned to that 1640cpuset. If it is due to a mempolicy's node(s) being exhausted, the allowed 1641memory represents the set of mempolicy nodes. If it is due to a memory 1642limit (or swap limit) being reached, the allowed memory is that configured 1643limit. Finally, if it is due to the entire system being out of memory, the 1644allowed memory represents all allocatable resources. 1645 1646The value of /proc/<pid>/oom_score_adj is added to the badness score before it 1647is used to determine which task to kill. Acceptable values range from -1000 1648(OOM_SCORE_ADJ_MIN) to +1000 (OOM_SCORE_ADJ_MAX). This allows userspace to 1649polarize the preference for oom killing either by always preferring a certain 1650task or completely disabling it. The lowest possible value, -1000, is 1651equivalent to disabling oom killing entirely for that task since it will always 1652report a badness score of 0. 1653 1654Consequently, it is very simple for userspace to define the amount of memory to 1655consider for each task. Setting a /proc/<pid>/oom_score_adj value of +500, for 1656example, is roughly equivalent to allowing the remainder of tasks sharing the 1657same system, cpuset, mempolicy, or memory controller resources to use at least 165850% more memory. A value of -500, on the other hand, would be roughly 1659equivalent to discounting 50% of the task's allowed memory from being considered 1660as scoring against the task. 1661 1662For backwards compatibility with previous kernels, /proc/<pid>/oom_adj may also 1663be used to tune the badness score. Its acceptable values range from -16 1664(OOM_ADJUST_MIN) to +15 (OOM_ADJUST_MAX) and a special value of -17 1665(OOM_DISABLE) to disable oom killing entirely for that task. Its value is 1666scaled linearly with /proc/<pid>/oom_score_adj. 1667 1668The value of /proc/<pid>/oom_score_adj may be reduced no lower than the last 1669value set by a CAP_SYS_RESOURCE process. To reduce the value any lower 1670requires CAP_SYS_RESOURCE. 1671 1672Caveat: when a parent task is selected, the oom killer will sacrifice any first 1673generation children with separate address spaces instead, if possible. This 1674avoids servers and important system daemons from being killed and loses the 1675minimal amount of work. 1676 1677 16783.2 /proc/<pid>/oom_score - Display current oom-killer score 1679------------------------------------------------------------- 1680 1681This file can be used to check the current score used by the oom-killer is for 1682any given <pid>. Use it together with /proc/<pid>/oom_score_adj to tune which 1683process should be killed in an out-of-memory situation. 1684 1685 16863.3 /proc/<pid>/io - Display the IO accounting fields 1687------------------------------------------------------- 1688 1689This file contains IO statistics for each running process 1690 1691Example 1692~~~~~~~ 1693 1694:: 1695 1696 test:/tmp # dd if=/dev/zero of=/tmp/test.dat & 1697 [1] 3828 1698 1699 test:/tmp # cat /proc/3828/io 1700 rchar: 323934931 1701 wchar: 323929600 1702 syscr: 632687 1703 syscw: 632675 1704 read_bytes: 0 1705 write_bytes: 323932160 1706 cancelled_write_bytes: 0 1707 1708 1709Description 1710~~~~~~~~~~~ 1711 1712rchar 1713^^^^^ 1714 1715I/O counter: chars read 1716The number of bytes which this task has caused to be read from storage. This 1717is simply the sum of bytes which this process passed to read() and pread(). 1718It includes things like tty IO and it is unaffected by whether or not actual 1719physical disk IO was required (the read might have been satisfied from 1720pagecache) 1721 1722 1723wchar 1724^^^^^ 1725 1726I/O counter: chars written 1727The number of bytes which this task has caused, or shall cause to be written 1728to disk. Similar caveats apply here as with rchar. 1729 1730 1731syscr 1732^^^^^ 1733 1734I/O counter: read syscalls 1735Attempt to count the number of read I/O operations, i.e. syscalls like read() 1736and pread(). 1737 1738 1739syscw 1740^^^^^ 1741 1742I/O counter: write syscalls 1743Attempt to count the number of write I/O operations, i.e. syscalls like 1744write() and pwrite(). 1745 1746 1747read_bytes 1748^^^^^^^^^^ 1749 1750I/O counter: bytes read 1751Attempt to count the number of bytes which this process really did cause to 1752be fetched from the storage layer. Done at the submit_bio() level, so it is 1753accurate for block-backed filesystems. <please add status regarding NFS and 1754CIFS at a later time> 1755 1756 1757write_bytes 1758^^^^^^^^^^^ 1759 1760I/O counter: bytes written 1761Attempt to count the number of bytes which this process caused to be sent to 1762the storage layer. This is done at page-dirtying time. 1763 1764 1765cancelled_write_bytes 1766^^^^^^^^^^^^^^^^^^^^^ 1767 1768The big inaccuracy here is truncate. If a process writes 1MB to a file and 1769then deletes the file, it will in fact perform no writeout. But it will have 1770been accounted as having caused 1MB of write. 1771In other words: The number of bytes which this process caused to not happen, 1772by truncating pagecache. A task can cause "negative" IO too. If this task 1773truncates some dirty pagecache, some IO which another task has been accounted 1774for (in its write_bytes) will not be happening. We _could_ just subtract that 1775from the truncating task's write_bytes, but there is information loss in doing 1776that. 1777 1778 1779.. Note:: 1780 1781 At its current implementation state, this is a bit racy on 32-bit machines: 1782 if process A reads process B's /proc/pid/io while process B is updating one 1783 of those 64-bit counters, process A could see an intermediate result. 1784 1785 1786More information about this can be found within the taskstats documentation in 1787Documentation/accounting. 1788 17893.4 /proc/<pid>/coredump_filter - Core dump filtering settings 1790--------------------------------------------------------------- 1791When a process is dumped, all anonymous memory is written to a core file as 1792long as the size of the core file isn't limited. But sometimes we don't want 1793to dump some memory segments, for example, huge shared memory or DAX. 1794Conversely, sometimes we want to save file-backed memory segments into a core 1795file, not only the individual files. 1796 1797/proc/<pid>/coredump_filter allows you to customize which memory segments 1798will be dumped when the <pid> process is dumped. coredump_filter is a bitmask 1799of memory types. If a bit of the bitmask is set, memory segments of the 1800corresponding memory type are dumped, otherwise they are not dumped. 1801 1802The following 9 memory types are supported: 1803 1804 - (bit 0) anonymous private memory 1805 - (bit 1) anonymous shared memory 1806 - (bit 2) file-backed private memory 1807 - (bit 3) file-backed shared memory 1808 - (bit 4) ELF header pages in file-backed private memory areas (it is 1809 effective only if the bit 2 is cleared) 1810 - (bit 5) hugetlb private memory 1811 - (bit 6) hugetlb shared memory 1812 - (bit 7) DAX private memory 1813 - (bit 8) DAX shared memory 1814 1815 Note that MMIO pages such as frame buffer are never dumped and vDSO pages 1816 are always dumped regardless of the bitmask status. 1817 1818 Note that bits 0-4 don't affect hugetlb or DAX memory. hugetlb memory is 1819 only affected by bit 5-6, and DAX is only affected by bits 7-8. 1820 1821The default value of coredump_filter is 0x33; this means all anonymous memory 1822segments, ELF header pages and hugetlb private memory are dumped. 1823 1824If you don't want to dump all shared memory segments attached to pid 1234, 1825write 0x31 to the process's proc file:: 1826 1827 $ echo 0x31 > /proc/1234/coredump_filter 1828 1829When a new process is created, the process inherits the bitmask status from its 1830parent. It is useful to set up coredump_filter before the program runs. 1831For example:: 1832 1833 $ echo 0x7 > /proc/self/coredump_filter 1834 $ ./some_program 1835 18363.5 /proc/<pid>/mountinfo - Information about mounts 1837-------------------------------------------------------- 1838 1839This file contains lines of the form:: 1840 1841 36 35 98:0 /mnt1 /mnt2 rw,noatime master:1 - ext3 /dev/root rw,errors=continue 1842 (1)(2)(3) (4) (5) (6) (7) (8) (9) (10) (11) 1843 1844 (1) mount ID: unique identifier of the mount (may be reused after umount) 1845 (2) parent ID: ID of parent (or of self for the top of the mount tree) 1846 (3) major:minor: value of st_dev for files on filesystem 1847 (4) root: root of the mount within the filesystem 1848 (5) mount point: mount point relative to the process's root 1849 (6) mount options: per mount options 1850 (7) optional fields: zero or more fields of the form "tag[:value]" 1851 (8) separator: marks the end of the optional fields 1852 (9) filesystem type: name of filesystem of the form "type[.subtype]" 1853 (10) mount source: filesystem specific information or "none" 1854 (11) super options: per super block options 1855 1856Parsers should ignore all unrecognised optional fields. Currently the 1857possible optional fields are: 1858 1859================ ============================================================== 1860shared:X mount is shared in peer group X 1861master:X mount is slave to peer group X 1862propagate_from:X mount is slave and receives propagation from peer group X [#]_ 1863unbindable mount is unbindable 1864================ ============================================================== 1865 1866.. [#] X is the closest dominant peer group under the process's root. If 1867 X is the immediate master of the mount, or if there's no dominant peer 1868 group under the same root, then only the "master:X" field is present 1869 and not the "propagate_from:X" field. 1870 1871For more information on mount propagation see: 1872 1873 Documentation/filesystems/sharedsubtree.txt 1874 1875 18763.6 /proc/<pid>/comm & /proc/<pid>/task/<tid>/comm 1877-------------------------------------------------------- 1878These files provide a method to access a tasks comm value. It also allows for 1879a task to set its own or one of its thread siblings comm value. The comm value 1880is limited in size compared to the cmdline value, so writing anything longer 1881then the kernel's TASK_COMM_LEN (currently 16 chars) will result in a truncated 1882comm value. 1883 1884 18853.7 /proc/<pid>/task/<tid>/children - Information about task children 1886------------------------------------------------------------------------- 1887This file provides a fast way to retrieve first level children pids 1888of a task pointed by <pid>/<tid> pair. The format is a space separated 1889stream of pids. 1890 1891Note the "first level" here -- if a child has own children they will 1892not be listed here, one needs to read /proc/<children-pid>/task/<tid>/children 1893to obtain the descendants. 1894 1895Since this interface is intended to be fast and cheap it doesn't 1896guarantee to provide precise results and some children might be 1897skipped, especially if they've exited right after we printed their 1898pids, so one need to either stop or freeze processes being inspected 1899if precise results are needed. 1900 1901 19023.8 /proc/<pid>/fdinfo/<fd> - Information about opened file 1903--------------------------------------------------------------- 1904This file provides information associated with an opened file. The regular 1905files have at least three fields -- 'pos', 'flags' and mnt_id. The 'pos' 1906represents the current offset of the opened file in decimal form [see lseek(2) 1907for details], 'flags' denotes the octal O_xxx mask the file has been 1908created with [see open(2) for details] and 'mnt_id' represents mount ID of 1909the file system containing the opened file [see 3.5 /proc/<pid>/mountinfo 1910for details]. 1911 1912A typical output is:: 1913 1914 pos: 0 1915 flags: 0100002 1916 mnt_id: 19 1917 1918All locks associated with a file descriptor are shown in its fdinfo too:: 1919 1920 lock: 1: FLOCK ADVISORY WRITE 359 00:13:11691 0 EOF 1921 1922The files such as eventfd, fsnotify, signalfd, epoll among the regular pos/flags 1923pair provide additional information particular to the objects they represent. 1924 1925Eventfd files 1926~~~~~~~~~~~~~ 1927 1928:: 1929 1930 pos: 0 1931 flags: 04002 1932 mnt_id: 9 1933 eventfd-count: 5a 1934 1935where 'eventfd-count' is hex value of a counter. 1936 1937Signalfd files 1938~~~~~~~~~~~~~~ 1939 1940:: 1941 1942 pos: 0 1943 flags: 04002 1944 mnt_id: 9 1945 sigmask: 0000000000000200 1946 1947where 'sigmask' is hex value of the signal mask associated 1948with a file. 1949 1950Epoll files 1951~~~~~~~~~~~ 1952 1953:: 1954 1955 pos: 0 1956 flags: 02 1957 mnt_id: 9 1958 tfd: 5 events: 1d data: ffffffffffffffff pos:0 ino:61af sdev:7 1959 1960where 'tfd' is a target file descriptor number in decimal form, 1961'events' is events mask being watched and the 'data' is data 1962associated with a target [see epoll(7) for more details]. 1963 1964The 'pos' is current offset of the target file in decimal form 1965[see lseek(2)], 'ino' and 'sdev' are inode and device numbers 1966where target file resides, all in hex format. 1967 1968Fsnotify files 1969~~~~~~~~~~~~~~ 1970For inotify files the format is the following:: 1971 1972 pos: 0 1973 flags: 02000000 1974 inotify wd:3 ino:9e7e sdev:800013 mask:800afce ignored_mask:0 fhandle-bytes:8 fhandle-type:1 f_handle:7e9e0000640d1b6d 1975 1976where 'wd' is a watch descriptor in decimal form, ie a target file 1977descriptor number, 'ino' and 'sdev' are inode and device where the 1978target file resides and the 'mask' is the mask of events, all in hex 1979form [see inotify(7) for more details]. 1980 1981If the kernel was built with exportfs support, the path to the target 1982file is encoded as a file handle. The file handle is provided by three 1983fields 'fhandle-bytes', 'fhandle-type' and 'f_handle', all in hex 1984format. 1985 1986If the kernel is built without exportfs support the file handle won't be 1987printed out. 1988 1989If there is no inotify mark attached yet the 'inotify' line will be omitted. 1990 1991For fanotify files the format is:: 1992 1993 pos: 0 1994 flags: 02 1995 mnt_id: 9 1996 fanotify flags:10 event-flags:0 1997 fanotify mnt_id:12 mflags:40 mask:38 ignored_mask:40000003 1998 fanotify ino:4f969 sdev:800013 mflags:0 mask:3b ignored_mask:40000000 fhandle-bytes:8 fhandle-type:1 f_handle:69f90400c275b5b4 1999 2000where fanotify 'flags' and 'event-flags' are values used in fanotify_init 2001call, 'mnt_id' is the mount point identifier, 'mflags' is the value of 2002flags associated with mark which are tracked separately from events 2003mask. 'ino', 'sdev' are target inode and device, 'mask' is the events 2004mask and 'ignored_mask' is the mask of events which are to be ignored. 2005All in hex format. Incorporation of 'mflags', 'mask' and 'ignored_mask' 2006does provide information about flags and mask used in fanotify_mark 2007call [see fsnotify manpage for details]. 2008 2009While the first three lines are mandatory and always printed, the rest is 2010optional and may be omitted if no marks created yet. 2011 2012Timerfd files 2013~~~~~~~~~~~~~ 2014 2015:: 2016 2017 pos: 0 2018 flags: 02 2019 mnt_id: 9 2020 clockid: 0 2021 ticks: 0 2022 settime flags: 01 2023 it_value: (0, 49406829) 2024 it_interval: (1, 0) 2025 2026where 'clockid' is the clock type and 'ticks' is the number of the timer expirations 2027that have occurred [see timerfd_create(2) for details]. 'settime flags' are 2028flags in octal form been used to setup the timer [see timerfd_settime(2) for 2029details]. 'it_value' is remaining time until the timer exiration. 2030'it_interval' is the interval for the timer. Note the timer might be set up 2031with TIMER_ABSTIME option which will be shown in 'settime flags', but 'it_value' 2032still exhibits timer's remaining time. 2033 20343.9 /proc/<pid>/map_files - Information about memory mapped files 2035--------------------------------------------------------------------- 2036This directory contains symbolic links which represent memory mapped files 2037the process is maintaining. Example output:: 2038 2039 | lr-------- 1 root root 64 Jan 27 11:24 333c600000-333c620000 -> /usr/lib64/ld-2.18.so 2040 | lr-------- 1 root root 64 Jan 27 11:24 333c81f000-333c820000 -> /usr/lib64/ld-2.18.so 2041 | lr-------- 1 root root 64 Jan 27 11:24 333c820000-333c821000 -> /usr/lib64/ld-2.18.so 2042 | ... 2043 | lr-------- 1 root root 64 Jan 27 11:24 35d0421000-35d0422000 -> /usr/lib64/libselinux.so.1 2044 | lr-------- 1 root root 64 Jan 27 11:24 400000-41a000 -> /usr/bin/ls 2045 2046The name of a link represents the virtual memory bounds of a mapping, i.e. 2047vm_area_struct::vm_start-vm_area_struct::vm_end. 2048 2049The main purpose of the map_files is to retrieve a set of memory mapped 2050files in a fast way instead of parsing /proc/<pid>/maps or 2051/proc/<pid>/smaps, both of which contain many more records. At the same 2052time one can open(2) mappings from the listings of two processes and 2053comparing their inode numbers to figure out which anonymous memory areas 2054are actually shared. 2055 20563.10 /proc/<pid>/timerslack_ns - Task timerslack value 2057--------------------------------------------------------- 2058This file provides the value of the task's timerslack value in nanoseconds. 2059This value specifies a amount of time that normal timers may be deferred 2060in order to coalesce timers and avoid unnecessary wakeups. 2061 2062This allows a task's interactivity vs power consumption trade off to be 2063adjusted. 2064 2065Writing 0 to the file will set the tasks timerslack to the default value. 2066 2067Valid values are from 0 - ULLONG_MAX 2068 2069An application setting the value must have PTRACE_MODE_ATTACH_FSCREDS level 2070permissions on the task specified to change its timerslack_ns value. 2071 20723.11 /proc/<pid>/patch_state - Livepatch patch operation state 2073----------------------------------------------------------------- 2074When CONFIG_LIVEPATCH is enabled, this file displays the value of the 2075patch state for the task. 2076 2077A value of '-1' indicates that no patch is in transition. 2078 2079A value of '0' indicates that a patch is in transition and the task is 2080unpatched. If the patch is being enabled, then the task hasn't been 2081patched yet. If the patch is being disabled, then the task has already 2082been unpatched. 2083 2084A value of '1' indicates that a patch is in transition and the task is 2085patched. If the patch is being enabled, then the task has already been 2086patched. If the patch is being disabled, then the task hasn't been 2087unpatched yet. 2088 20893.12 /proc/<pid>/arch_status - task architecture specific status 2090------------------------------------------------------------------- 2091When CONFIG_PROC_PID_ARCH_STATUS is enabled, this file displays the 2092architecture specific status of the task. 2093 2094Example 2095~~~~~~~ 2096 2097:: 2098 2099 $ cat /proc/6753/arch_status 2100 AVX512_elapsed_ms: 8 2101 2102Description 2103~~~~~~~~~~~ 2104 2105x86 specific entries: 2106~~~~~~~~~~~~~~~~~~~~~ 2107 2108AVX512_elapsed_ms: 2109^^^^^^^^^^^^^^^^^^ 2110 2111 If AVX512 is supported on the machine, this entry shows the milliseconds 2112 elapsed since the last time AVX512 usage was recorded. The recording 2113 happens on a best effort basis when a task is scheduled out. This means 2114 that the value depends on two factors: 2115 2116 1) The time which the task spent on the CPU without being scheduled 2117 out. With CPU isolation and a single runnable task this can take 2118 several seconds. 2119 2120 2) The time since the task was scheduled out last. Depending on the 2121 reason for being scheduled out (time slice exhausted, syscall ...) 2122 this can be arbitrary long time. 2123 2124 As a consequence the value cannot be considered precise and authoritative 2125 information. The application which uses this information has to be aware 2126 of the overall scenario on the system in order to determine whether a 2127 task is a real AVX512 user or not. Precise information can be obtained 2128 with performance counters. 2129 2130 A special value of '-1' indicates that no AVX512 usage was recorded, thus 2131 the task is unlikely an AVX512 user, but depends on the workload and the 2132 scheduling scenario, it also could be a false negative mentioned above. 2133 2134Configuring procfs 2135------------------ 2136 21374.1 Mount options 2138--------------------- 2139 2140The following mount options are supported: 2141 2142 ========= ======================================================== 2143 hidepid= Set /proc/<pid>/ access mode. 2144 gid= Set the group authorized to learn processes information. 2145 ========= ======================================================== 2146 2147hidepid=0 means classic mode - everybody may access all /proc/<pid>/ directories 2148(default). 2149 2150hidepid=1 means users may not access any /proc/<pid>/ directories but their 2151own. Sensitive files like cmdline, sched*, status are now protected against 2152other users. This makes it impossible to learn whether any user runs 2153specific program (given the program doesn't reveal itself by its behaviour). 2154As an additional bonus, as /proc/<pid>/cmdline is unaccessible for other users, 2155poorly written programs passing sensitive information via program arguments are 2156now protected against local eavesdroppers. 2157 2158hidepid=2 means hidepid=1 plus all /proc/<pid>/ will be fully invisible to other 2159users. It doesn't mean that it hides a fact whether a process with a specific 2160pid value exists (it can be learned by other means, e.g. by "kill -0 $PID"), 2161but it hides process' uid and gid, which may be learned by stat()'ing 2162/proc/<pid>/ otherwise. It greatly complicates an intruder's task of gathering 2163information about running processes, whether some daemon runs with elevated 2164privileges, whether other user runs some sensitive program, whether other users 2165run any program at all, etc. 2166 2167gid= defines a group authorized to learn processes information otherwise 2168prohibited by hidepid=. If you use some daemon like identd which needs to learn 2169information about processes information, just add identd to this group. 2170