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2 T H E /proc F I L E S Y S T E M
3 ------------------------------------------------------------------------------
4 /proc/sys Terrehon Bowden <terrehon@pacbell.net> October 7 1999
5 Bodo Bauer <bb@ricochet.net>
7 2.4.x update Jorge Nerin <comandante@zaralinux.com> November 14 2000
8 move /proc/sys Shen Feng <shen@cn.fujitsu.com> April 1 2009
9 ------------------------------------------------------------------------------
10 Version 1.3 Kernel version 2.2.12
11 Kernel version 2.4.0-test11-pre4
12 ------------------------------------------------------------------------------
13 fixes/update part 1.1 Stefani Seibold <stefani@seibold.net> June 9 2009
15 Table of Contents
16 -----------------
18 0 Preface
19 0.1 Introduction/Credits
20 0.2 Legal Stuff
22 1 Collecting System Information
23 1.1 Process-Specific Subdirectories
24 1.2 Kernel data
25 1.3 IDE devices in /proc/ide
26 1.4 Networking info in /proc/net
27 1.5 SCSI info
28 1.6 Parallel port info in /proc/parport
29 1.7 TTY info in /proc/tty
30 1.8 Miscellaneous kernel statistics in /proc/stat
31 1.9 Ext4 file system parameters
33 2 Modifying System Parameters
35 3 Per-Process Parameters
36 3.1 /proc/<pid>/oom_adj - Adjust the oom-killer score
37 3.2 /proc/<pid>/oom_score - Display current oom-killer score
38 3.3 /proc/<pid>/io - Display the IO accounting fields
39 3.4 /proc/<pid>/coredump_filter - Core dump filtering settings
40 3.5 /proc/<pid>/mountinfo - Information about mounts
41 3.6 /proc/<pid>/comm & /proc/<pid>/task/<tid>/comm
44 ------------------------------------------------------------------------------
45 Preface
46 ------------------------------------------------------------------------------
48 0.1 Introduction/Credits
49 ------------------------
51 This documentation is part of a soon (or so we hope) to be released book on
52 the SuSE Linux distribution. As there is no complete documentation for the
53 /proc file system and we've used many freely available sources to write these
54 chapters, it seems only fair to give the work back to the Linux community.
55 This work is based on the 2.2.* kernel version and the upcoming 2.4.*. I'm
56 afraid it's still far from complete, but we hope it will be useful. As far as
57 we know, it is the first 'all-in-one' document about the /proc file system. It
58 is focused on the Intel x86 hardware, so if you are looking for PPC, ARM,
59 SPARC, AXP, etc., features, you probably won't find what you are looking for.
60 It also only covers IPv4 networking, not IPv6 nor other protocols - sorry. But
61 additions and patches are welcome and will be added to this document if you
62 mail them to Bodo.
64 We'd like to thank Alan Cox, Rik van Riel, and Alexey Kuznetsov and a lot of
65 other people for help compiling this documentation. We'd also like to extend a
66 special thank you to Andi Kleen for documentation, which we relied on heavily
67 to create this document, as well as the additional information he provided.
68 Thanks to everybody else who contributed source or docs to the Linux kernel
69 and helped create a great piece of software... :)
71 If you have any comments, corrections or additions, please don't hesitate to
72 contact Bodo Bauer at bb@ricochet.net. We'll be happy to add them to this
73 document.
75 The latest version of this document is available online at
76 http://skaro.nightcrawler.com/~bb/Docs/Proc as HTML version.
78 If the above direction does not works for you, ypu could try the kernel
79 mailing list at linux-kernel@vger.kernel.org and/or try to reach me at
80 comandante@zaralinux.com.
82 0.2 Legal Stuff
83 ---------------
85 We don't guarantee the correctness of this document, and if you come to us
86 complaining about how you screwed up your system because of incorrect
87 documentation, we won't feel responsible...
89 ------------------------------------------------------------------------------
90 CHAPTER 1: COLLECTING SYSTEM INFORMATION
91 ------------------------------------------------------------------------------
93 ------------------------------------------------------------------------------
94 In This Chapter
95 ------------------------------------------------------------------------------
96 * Investigating the properties of the pseudo file system /proc and its
97 ability to provide information on the running Linux system
98 * Examining /proc's structure
99 * Uncovering various information about the kernel and the processes running
100 on the system
101 ------------------------------------------------------------------------------
104 The proc file system acts as an interface to internal data structures in the
105 kernel. It can be used to obtain information about the system and to change
106 certain kernel parameters at runtime (sysctl).
108 First, we'll take a look at the read-only parts of /proc. In Chapter 2, we
109 show you how you can use /proc/sys to change settings.
111 1.1 Process-Specific Subdirectories
112 -----------------------------------
114 The directory /proc contains (among other things) one subdirectory for each
115 process running on the system, which is named after the process ID (PID).
117 The link self points to the process reading the file system. Each process
118 subdirectory has the entries listed in Table 1-1.
121 Table 1-1: Process specific entries in /proc
122 ..............................................................................
123 File Content
124 clear_refs Clears page referenced bits shown in smaps output
125 cmdline Command line arguments
126 cpu Current and last cpu in which it was executed (2.4)(smp)
127 cwd Link to the current working directory
128 environ Values of environment variables
129 exe Link to the executable of this process
130 fd Directory, which contains all file descriptors
131 maps Memory maps to executables and library files (2.4)
132 mem Memory held by this process
133 root Link to the root directory of this process
134 stat Process status
135 statm Process memory status information
136 status Process status in human readable form
137 wchan If CONFIG_KALLSYMS is set, a pre-decoded wchan
138 stack Report full stack trace, enable via CONFIG_STACKTRACE
139 smaps a extension based on maps, showing the memory consumption of
140 each mapping
141 ..............................................................................
143 For example, to get the status information of a process, all you have to do is
144 read the file /proc/PID/status:
146 >cat /proc/self/status
147 Name: cat
148 State: R (running)
149 Tgid: 5452
150 Pid: 5452
151 PPid: 743
152 TracerPid: 0 (2.4)
153 Uid: 501 501 501 501
154 Gid: 100 100 100 100
155 FDSize: 256
156 Groups: 100 14 16
157 VmPeak: 5004 kB
158 VmSize: 5004 kB
159 VmLck: 0 kB
160 VmHWM: 476 kB
161 VmRSS: 476 kB
162 VmData: 156 kB
163 VmStk: 88 kB
164 VmExe: 68 kB
165 VmLib: 1412 kB
166 VmPTE: 20 kb
167 Threads: 1
168 SigQ: 0/28578
169 SigPnd: 0000000000000000
170 ShdPnd: 0000000000000000
171 SigBlk: 0000000000000000
172 SigIgn: 0000000000000000
173 SigCgt: 0000000000000000
174 CapInh: 00000000fffffeff
175 CapPrm: 0000000000000000
176 CapEff: 0000000000000000
177 CapBnd: ffffffffffffffff
178 voluntary_ctxt_switches: 0
179 nonvoluntary_ctxt_switches: 1
181 This shows you nearly the same information you would get if you viewed it with
182 the ps command. In fact, ps uses the proc file system to obtain its
183 information. But you get a more detailed view of the process by reading the
184 file /proc/PID/status. It fields are described in table 1-2.
186 The statm file contains more detailed information about the process
187 memory usage. Its seven fields are explained in Table 1-3. The stat file
188 contains details information about the process itself. Its fields are
189 explained in Table 1-4.
191 Table 1-2: Contents of the statm files (as of 2.6.30-rc7)
192 ..............................................................................
193 Field Content
194 Name filename of the executable
195 State state (R is running, S is sleeping, D is sleeping
196 in an uninterruptible wait, Z is zombie,
197 T is traced or stopped)
198 Tgid thread group ID
199 Pid process id
200 PPid process id of the parent process
201 TracerPid PID of process tracing this process (0 if not)
202 Uid Real, effective, saved set, and file system UIDs
203 Gid Real, effective, saved set, and file system GIDs
204 FDSize number of file descriptor slots currently allocated
205 Groups supplementary group list
206 VmPeak peak virtual memory size
207 VmSize total program size
208 VmLck locked memory size
209 VmHWM peak resident set size ("high water mark")
210 VmRSS size of memory portions
211 VmData size of data, stack, and text segments
212 VmStk size of data, stack, and text segments
213 VmExe size of text segment
214 VmLib size of shared library code
215 VmPTE size of page table entries
216 Threads number of threads
217 SigQ number of signals queued/max. number for queue
218 SigPnd bitmap of pending signals for the thread
219 ShdPnd bitmap of shared pending signals for the process
220 SigBlk bitmap of blocked signals
221 SigIgn bitmap of ignored signals
222 SigCgt bitmap of catched signals
223 CapInh bitmap of inheritable capabilities
224 CapPrm bitmap of permitted capabilities
225 CapEff bitmap of effective capabilities
226 CapBnd bitmap of capabilities bounding set
227 Cpus_allowed mask of CPUs on which this process may run
228 Cpus_allowed_list Same as previous, but in "list format"
229 Mems_allowed mask of memory nodes allowed to this process
230 Mems_allowed_list Same as previous, but in "list format"
231 voluntary_ctxt_switches number of voluntary context switches
232 nonvoluntary_ctxt_switches number of non voluntary context switches
233 ..............................................................................
235 Table 1-3: Contents of the statm files (as of 2.6.8-rc3)
236 ..............................................................................
237 Field Content
238 size total program size (pages) (same as VmSize in status)
239 resident size of memory portions (pages) (same as VmRSS in status)
240 shared number of pages that are shared (i.e. backed by a file)
241 trs number of pages that are 'code' (not including libs; broken,
242 includes data segment)
243 lrs number of pages of library (always 0 on 2.6)
244 drs number of pages of data/stack (including libs; broken,
245 includes library text)
246 dt number of dirty pages (always 0 on 2.6)
247 ..............................................................................
250 Table 1-4: Contents of the stat files (as of 2.6.30-rc7)
251 ..............................................................................
252 Field Content
253 pid process id
254 tcomm filename of the executable
255 state state (R is running, S is sleeping, D is sleeping in an
256 uninterruptible wait, Z is zombie, T is traced or stopped)
257 ppid process id of the parent process
258 pgrp pgrp of the process
259 sid session id
260 tty_nr tty the process uses
261 tty_pgrp pgrp of the tty
262 flags task flags
263 min_flt number of minor faults
264 cmin_flt number of minor faults with child's
265 maj_flt number of major faults
266 cmaj_flt number of major faults with child's
267 utime user mode jiffies
268 stime kernel mode jiffies
269 cutime user mode jiffies with child's
270 cstime kernel mode jiffies with child's
271 priority priority level
272 nice nice level
273 num_threads number of threads
274 it_real_value (obsolete, always 0)
275 start_time time the process started after system boot
276 vsize virtual memory size
277 rss resident set memory size
278 rsslim current limit in bytes on the rss
279 start_code address above which program text can run
280 end_code address below which program text can run
281 start_stack address of the start of the stack
282 esp current value of ESP
283 eip current value of EIP
284 pending bitmap of pending signals
285 blocked bitmap of blocked signals
286 sigign bitmap of ignored signals
287 sigcatch bitmap of catched signals
288 wchan address where process went to sleep
289 0 (place holder)
290 0 (place holder)
291 exit_signal signal to send to parent thread on exit
292 task_cpu which CPU the task is scheduled on
293 rt_priority realtime priority
294 policy scheduling policy (man sched_setscheduler)
295 blkio_ticks time spent waiting for block IO
296 gtime guest time of the task in jiffies
297 cgtime guest time of the task children in jiffies
298 ..............................................................................
300 The /proc/PID/map file containing the currently mapped memory regions and
301 their access permissions.
303 The format is:
305 address perms offset dev inode pathname
307 08048000-08049000 r-xp 00000000 03:00 8312 /opt/test
308 08049000-0804a000 rw-p 00001000 03:00 8312 /opt/test
309 0804a000-0806b000 rw-p 00000000 00:00 0 [heap]
310 a7cb1000-a7cb2000 ---p 00000000 00:00 0
311 a7cb2000-a7eb2000 rw-p 00000000 00:00 0 [threadstack:001ff4b4]
312 a7eb2000-a7eb3000 ---p 00000000 00:00 0
313 a7eb3000-a7ed5000 rw-p 00000000 00:00 0
314 a7ed5000-a8008000 r-xp 00000000 03:00 4222 /lib/libc.so.6
315 a8008000-a800a000 r--p 00133000 03:00 4222 /lib/libc.so.6
316 a800a000-a800b000 rw-p 00135000 03:00 4222 /lib/libc.so.6
317 a800b000-a800e000 rw-p 00000000 00:00 0
318 a800e000-a8022000 r-xp 00000000 03:00 14462 /lib/libpthread.so.0
319 a8022000-a8023000 r--p 00013000 03:00 14462 /lib/libpthread.so.0
320 a8023000-a8024000 rw-p 00014000 03:00 14462 /lib/libpthread.so.0
321 a8024000-a8027000 rw-p 00000000 00:00 0
322 a8027000-a8043000 r-xp 00000000 03:00 8317 /lib/ld-linux.so.2
323 a8043000-a8044000 r--p 0001b000 03:00 8317 /lib/ld-linux.so.2
324 a8044000-a8045000 rw-p 0001c000 03:00 8317 /lib/ld-linux.so.2
325 aff35000-aff4a000 rw-p 00000000 00:00 0 [stack]
326 ffffe000-fffff000 r-xp 00000000 00:00 0 [vdso]
328 where "address" is the address space in the process that it occupies, "perms"
329 is a set of permissions:
331 r = read
332 w = write
333 x = execute
334 s = shared
335 p = private (copy on write)
337 "offset" is the offset into the mapping, "dev" is the device (major:minor), and
338 "inode" is the inode on that device. 0 indicates that no inode is associated
339 with the memory region, as the case would be with BSS (uninitialized data).
340 The "pathname" shows the name associated file for this mapping. If the mapping
341 is not associated with a file:
343 [heap] = the heap of the program
344 [stack] = the stack of the main process
345 [vdso] = the "virtual dynamic shared object",
346 the kernel system call handler
347 [threadstack:xxxxxxxx] = the stack of the thread, xxxxxxxx is the stack size
349 or if empty, the mapping is anonymous.
352 The /proc/PID/smaps is an extension based on maps, showing the memory
353 consumption for each of the process's mappings. For each of mappings there
354 is a series of lines such as the following:
356 08048000-080bc000 r-xp 00000000 03:02 13130 /bin/bash
357 Size: 1084 kB
358 Rss: 892 kB
359 Pss: 374 kB
360 Shared_Clean: 892 kB
361 Shared_Dirty: 0 kB
362 Private_Clean: 0 kB
363 Private_Dirty: 0 kB
364 Referenced: 892 kB
365 Swap: 0 kB
366 KernelPageSize: 4 kB
367 MMUPageSize: 4 kB
369 The first of these lines shows the same information as is displayed for the
370 mapping in /proc/PID/maps. The remaining lines show the size of the mapping,
371 the amount of the mapping that is currently resident in RAM, the "proportional
372 set size” (divide each shared page by the number of processes sharing it), the
373 number of clean and dirty shared pages in the mapping, and the number of clean
374 and dirty private pages in the mapping. The "Referenced" indicates the amount
375 of memory currently marked as referenced or accessed.
377 This file is only present if the CONFIG_MMU kernel configuration option is
378 enabled.
380 The /proc/PID/clear_refs is used to reset the PG_Referenced and ACCESSED/YOUNG
381 bits on both physical and virtual pages associated with a process.
382 To clear the bits for all the pages associated with the process
383 > echo 1 > /proc/PID/clear_refs
385 To clear the bits for the anonymous pages associated with the process
386 > echo 2 > /proc/PID/clear_refs
388 To clear the bits for the file mapped pages associated with the process
389 > echo 3 > /proc/PID/clear_refs
390 Any other value written to /proc/PID/clear_refs will have no effect.
393 1.2 Kernel data
394 ---------------
396 Similar to the process entries, the kernel data files give information about
397 the running kernel. The files used to obtain this information are contained in
398 /proc and are listed in Table 1-5. Not all of these will be present in your
399 system. It depends on the kernel configuration and the loaded modules, which
400 files are there, and which are missing.
402 Table 1-5: Kernel info in /proc
403 ..............................................................................
404 File Content
405 apm Advanced power management info
406 buddyinfo Kernel memory allocator information (see text) (2.5)
407 bus Directory containing bus specific information
408 cmdline Kernel command line
409 cpuinfo Info about the CPU
410 devices Available devices (block and character)
411 dma Used DMS channels
412 filesystems Supported filesystems
413 driver Various drivers grouped here, currently rtc (2.4)
414 execdomains Execdomains, related to security (2.4)
415 fb Frame Buffer devices (2.4)
416 fs File system parameters, currently nfs/exports (2.4)
417 ide Directory containing info about the IDE subsystem
418 interrupts Interrupt usage
419 iomem Memory map (2.4)
420 ioports I/O port usage
421 irq Masks for irq to cpu affinity (2.4)(smp?)
422 isapnp ISA PnP (Plug&Play) Info (2.4)
423 kcore Kernel core image (can be ELF or A.OUT(deprecated in 2.4))
424 kmsg Kernel messages
425 ksyms Kernel symbol table
426 loadavg Load average of last 1, 5 & 15 minutes
427 locks Kernel locks
428 meminfo Memory info
429 misc Miscellaneous
430 modules List of loaded modules
431 mounts Mounted filesystems
432 net Networking info (see text)
433 partitions Table of partitions known to the system
434 pci Deprecated info of PCI bus (new way -> /proc/bus/pci/,
435 decoupled by lspci (2.4)
436 rtc Real time clock
437 scsi SCSI info (see text)
438 slabinfo Slab pool info
439 softirqs softirq usage
440 stat Overall statistics
441 swaps Swap space utilization
442 sys See chapter 2
443 sysvipc Info of SysVIPC Resources (msg, sem, shm) (2.4)
444 tty Info of tty drivers
445 uptime System uptime
446 version Kernel version
447 video bttv info of video resources (2.4)
448 vmallocinfo Show vmalloced areas
449 ..............................................................................
451 You can, for example, check which interrupts are currently in use and what
452 they are used for by looking in the file /proc/interrupts:
454 > cat /proc/interrupts
455 CPU0
456 0: 8728810 XT-PIC timer
457 1: 895 XT-PIC keyboard
458 2: 0 XT-PIC cascade
459 3: 531695 XT-PIC aha152x
460 4: 2014133 XT-PIC serial
461 5: 44401 XT-PIC pcnet_cs
462 8: 2 XT-PIC rtc
463 11: 8 XT-PIC i82365
464 12: 182918 XT-PIC PS/2 Mouse
465 13: 1 XT-PIC fpu
466 14: 1232265 XT-PIC ide0
467 15: 7 XT-PIC ide1
468 NMI: 0
470 In 2.4.* a couple of lines where added to this file LOC & ERR (this time is the
471 output of a SMP machine):
473 > cat /proc/interrupts
475 CPU0 CPU1
476 0: 1243498 1214548 IO-APIC-edge timer
477 1: 8949 8958 IO-APIC-edge keyboard
478 2: 0 0 XT-PIC cascade
479 5: 11286 10161 IO-APIC-edge soundblaster
480 8: 1 0 IO-APIC-edge rtc
481 9: 27422 27407 IO-APIC-edge 3c503
482 12: 113645 113873 IO-APIC-edge PS/2 Mouse
483 13: 0 0 XT-PIC fpu
484 14: 22491 24012 IO-APIC-edge ide0
485 15: 2183 2415 IO-APIC-edge ide1
486 17: 30564 30414 IO-APIC-level eth0
487 18: 177 164 IO-APIC-level bttv
488 NMI: 2457961 2457959
489 LOC: 2457882 2457881
490 ERR: 2155
492 NMI is incremented in this case because every timer interrupt generates a NMI
493 (Non Maskable Interrupt) which is used by the NMI Watchdog to detect lockups.
495 LOC is the local interrupt counter of the internal APIC of every CPU.
497 ERR is incremented in the case of errors in the IO-APIC bus (the bus that
498 connects the CPUs in a SMP system. This means that an error has been detected,
499 the IO-APIC automatically retry the transmission, so it should not be a big
500 problem, but you should read the SMP-FAQ.
502 In 2.6.2* /proc/interrupts was expanded again. This time the goal was for
503 /proc/interrupts to display every IRQ vector in use by the system, not
504 just those considered 'most important'. The new vectors are:
506 THR -- interrupt raised when a machine check threshold counter
507 (typically counting ECC corrected errors of memory or cache) exceeds
508 a configurable threshold. Only available on some systems.
510 TRM -- a thermal event interrupt occurs when a temperature threshold
511 has been exceeded for the CPU. This interrupt may also be generated
512 when the temperature drops back to normal.
514 SPU -- a spurious interrupt is some interrupt that was raised then lowered
515 by some IO device before it could be fully processed by the APIC. Hence
516 the APIC sees the interrupt but does not know what device it came from.
517 For this case the APIC will generate the interrupt with a IRQ vector
518 of 0xff. This might also be generated by chipset bugs.
520 RES, CAL, TLB -- rescheduling, call and TLB flush interrupts are
521 sent from one CPU to another per the needs of the OS. Typically,
522 their statistics are used by kernel developers and interested users to
523 determine the occurrence of interrupts of the given type.
525 The above IRQ vectors are displayed only when relevent. For example,
526 the threshold vector does not exist on x86_64 platforms. Others are
527 suppressed when the system is a uniprocessor. As of this writing, only
528 i386 and x86_64 platforms support the new IRQ vector displays.
530 Of some interest is the introduction of the /proc/irq directory to 2.4.
531 It could be used to set IRQ to CPU affinity, this means that you can "hook" an
532 IRQ to only one CPU, or to exclude a CPU of handling IRQs. The contents of the
533 irq subdir is one subdir for each IRQ, and two files; default_smp_affinity and
534 prof_cpu_mask.
536 For example
537 > ls /proc/irq/
538 0 10 12 14 16 18 2 4 6 8 prof_cpu_mask
539 1 11 13 15 17 19 3 5 7 9 default_smp_affinity
540 > ls /proc/irq/0/
541 smp_affinity
543 smp_affinity is a bitmask, in which you can specify which CPUs can handle the
544 IRQ, you can set it by doing:
546 > echo 1 > /proc/irq/10/smp_affinity
548 This means that only the first CPU will handle the IRQ, but you can also echo
549 5 which means that only the first and fourth CPU can handle the IRQ.
551 The contents of each smp_affinity file is the same by default:
553 > cat /proc/irq/0/smp_affinity
554 ffffffff
556 The default_smp_affinity mask applies to all non-active IRQs, which are the
557 IRQs which have not yet been allocated/activated, and hence which lack a
558 /proc/irq/[0-9]* directory.
560 prof_cpu_mask specifies which CPUs are to be profiled by the system wide
561 profiler. Default value is ffffffff (all cpus).
563 The way IRQs are routed is handled by the IO-APIC, and it's Round Robin
564 between all the CPUs which are allowed to handle it. As usual the kernel has
565 more info than you and does a better job than you, so the defaults are the
566 best choice for almost everyone.
568 There are three more important subdirectories in /proc: net, scsi, and sys.
569 The general rule is that the contents, or even the existence of these
570 directories, depend on your kernel configuration. If SCSI is not enabled, the
571 directory scsi may not exist. The same is true with the net, which is there
572 only when networking support is present in the running kernel.
574 The slabinfo file gives information about memory usage at the slab level.
575 Linux uses slab pools for memory management above page level in version 2.2.
576 Commonly used objects have their own slab pool (such as network buffers,
577 directory cache, and so on).
579 ..............................................................................
581 > cat /proc/buddyinfo
583 Node 0, zone DMA 0 4 5 4 4 3 ...
584 Node 0, zone Normal 1 0 0 1 101 8 ...
585 Node 0, zone HighMem 2 0 0 1 1 0 ...
587 Memory fragmentation is a problem under some workloads, and buddyinfo is a
588 useful tool for helping diagnose these problems. Buddyinfo will give you a
589 clue as to how big an area you can safely allocate, or why a previous
590 allocation failed.
592 Each column represents the number of pages of a certain order which are
593 available. In this case, there are 0 chunks of 2^0*PAGE_SIZE available in
594 ZONE_DMA, 4 chunks of 2^1*PAGE_SIZE in ZONE_DMA, 101 chunks of 2^4*PAGE_SIZE
595 available in ZONE_NORMAL, etc...
597 ..............................................................................
599 meminfo:
601 Provides information about distribution and utilization of memory. This
602 varies by architecture and compile options. The following is from a
603 16GB PIII, which has highmem enabled. You may not have all of these fields.
605 > cat /proc/meminfo
608 MemTotal: 16344972 kB
609 MemFree: 13634064 kB
610 Buffers: 3656 kB
611 Cached: 1195708 kB
612 SwapCached: 0 kB
613 Active: 891636 kB
614 Inactive: 1077224 kB
615 HighTotal: 15597528 kB
616 HighFree: 13629632 kB
617 LowTotal: 747444 kB
618 LowFree: 4432 kB
619 SwapTotal: 0 kB
620 SwapFree: 0 kB
621 Dirty: 968 kB
622 Writeback: 0 kB
623 AnonPages: 861800 kB
624 Mapped: 280372 kB
625 Slab: 284364 kB
626 SReclaimable: 159856 kB
627 SUnreclaim: 124508 kB
628 PageTables: 24448 kB
629 NFS_Unstable: 0 kB
630 Bounce: 0 kB
631 WritebackTmp: 0 kB
632 CommitLimit: 7669796 kB
633 Committed_AS: 100056 kB
634 VmallocTotal: 112216 kB
635 VmallocUsed: 428 kB
636 VmallocChunk: 111088 kB
638 MemTotal: Total usable ram (i.e. physical ram minus a few reserved
639 bits and the kernel binary code)
640 MemFree: The sum of LowFree+HighFree
641 Buffers: Relatively temporary storage for raw disk blocks
642 shouldn't get tremendously large (20MB or so)
643 Cached: in-memory cache for files read from the disk (the
644 pagecache). Doesn't include SwapCached
645 SwapCached: Memory that once was swapped out, is swapped back in but
646 still also is in the swapfile (if memory is needed it
647 doesn't need to be swapped out AGAIN because it is already
648 in the swapfile. This saves I/O)
649 Active: Memory that has been used more recently and usually not
650 reclaimed unless absolutely necessary.
651 Inactive: Memory which has been less recently used. It is more
652 eligible to be reclaimed for other purposes
653 HighTotal:
654 HighFree: Highmem is all memory above ~860MB of physical memory
655 Highmem areas are for use by userspace programs, or
656 for the pagecache. The kernel must use tricks to access
657 this memory, making it slower to access than lowmem.
658 LowTotal:
659 LowFree: Lowmem is memory which can be used for everything that
660 highmem can be used for, but it is also available for the
661 kernel's use for its own data structures. Among many
662 other things, it is where everything from the Slab is
663 allocated. Bad things happen when you're out of lowmem.
664 SwapTotal: total amount of swap space available
665 SwapFree: Memory which has been evicted from RAM, and is temporarily
666 on the disk
667 Dirty: Memory which is waiting to get written back to the disk
668 Writeback: Memory which is actively being written back to the disk
669 AnonPages: Non-file backed pages mapped into userspace page tables
670 Mapped: files which have been mmaped, such as libraries
671 Slab: in-kernel data structures cache
672 SReclaimable: Part of Slab, that might be reclaimed, such as caches
673 SUnreclaim: Part of Slab, that cannot be reclaimed on memory pressure
674 PageTables: amount of memory dedicated to the lowest level of page
675 tables.
676 NFS_Unstable: NFS pages sent to the server, but not yet committed to stable
677 storage
678 Bounce: Memory used for block device "bounce buffers"
679 WritebackTmp: Memory used by FUSE for temporary writeback buffers
680 CommitLimit: Based on the overcommit ratio ('vm.overcommit_ratio'),
681 this is the total amount of memory currently available to
682 be allocated on the system. This limit is only adhered to
683 if strict overcommit accounting is enabled (mode 2 in
684 'vm.overcommit_memory').
685 The CommitLimit is calculated with the following formula:
686 CommitLimit = ('vm.overcommit_ratio' * Physical RAM) + Swap
687 For example, on a system with 1G of physical RAM and 7G
688 of swap with a `vm.overcommit_ratio` of 30 it would
689 yield a CommitLimit of 7.3G.
690 For more details, see the memory overcommit documentation
691 in vm/overcommit-accounting.
692 Committed_AS: The amount of memory presently allocated on the system.
693 The committed memory is a sum of all of the memory which
694 has been allocated by processes, even if it has not been
695 "used" by them as of yet. A process which malloc()'s 1G
696 of memory, but only touches 300M of it will only show up
697 as using 300M of memory even if it has the address space
698 allocated for the entire 1G. This 1G is memory which has
699 been "committed" to by the VM and can be used at any time
700 by the allocating application. With strict overcommit
701 enabled on the system (mode 2 in 'vm.overcommit_memory'),
702 allocations which would exceed the CommitLimit (detailed
703 above) will not be permitted. This is useful if one needs
704 to guarantee that processes will not fail due to lack of
705 memory once that memory has been successfully allocated.
706 VmallocTotal: total size of vmalloc memory area
707 VmallocUsed: amount of vmalloc area which is used
708 VmallocChunk: largest contiguous block of vmalloc area which is free
710 ..............................................................................
712 vmallocinfo:
714 Provides information about vmalloced/vmaped areas. One line per area,
715 containing the virtual address range of the area, size in bytes,
716 caller information of the creator, and optional information depending
717 on the kind of area :
719 pages=nr number of pages
720 phys=addr if a physical address was specified
721 ioremap I/O mapping (ioremap() and friends)
722 vmalloc vmalloc() area
723 vmap vmap()ed pages
724 user VM_USERMAP area
725 vpages buffer for pages pointers was vmalloced (huge area)
726 N<node>=nr (Only on NUMA kernels)
727 Number of pages allocated on memory node <node>
729 > cat /proc/vmallocinfo
730 0xffffc20000000000-0xffffc20000201000 2101248 alloc_large_system_hash+0x204 ...
731 /0x2c0 pages=512 vmalloc N0=128 N1=128 N2=128 N3=128
732 0xffffc20000201000-0xffffc20000302000 1052672 alloc_large_system_hash+0x204 ...
733 /0x2c0 pages=256 vmalloc N0=64 N1=64 N2=64 N3=64
734 0xffffc20000302000-0xffffc20000304000 8192 acpi_tb_verify_table+0x21/0x4f...
735 phys=7fee8000 ioremap
736 0xffffc20000304000-0xffffc20000307000 12288 acpi_tb_verify_table+0x21/0x4f...
737 phys=7fee7000 ioremap
738 0xffffc2000031d000-0xffffc2000031f000 8192 init_vdso_vars+0x112/0x210
739 0xffffc2000031f000-0xffffc2000032b000 49152 cramfs_uncompress_init+0x2e ...
740 /0x80 pages=11 vmalloc N0=3 N1=3 N2=2 N3=3
741 0xffffc2000033a000-0xffffc2000033d000 12288 sys_swapon+0x640/0xac0 ...
742 pages=2 vmalloc N1=2
743 0xffffc20000347000-0xffffc2000034c000 20480 xt_alloc_table_info+0xfe ...
744 /0x130 [x_tables] pages=4 vmalloc N0=4
745 0xffffffffa0000000-0xffffffffa000f000 61440 sys_init_module+0xc27/0x1d00 ...
746 pages=14 vmalloc N2=14
747 0xffffffffa000f000-0xffffffffa0014000 20480 sys_init_module+0xc27/0x1d00 ...
748 pages=4 vmalloc N1=4
749 0xffffffffa0014000-0xffffffffa0017000 12288 sys_init_module+0xc27/0x1d00 ...
750 pages=2 vmalloc N1=2
751 0xffffffffa0017000-0xffffffffa0022000 45056 sys_init_module+0xc27/0x1d00 ...
752 pages=10 vmalloc N0=10
754 ..............................................................................
756 softirqs:
758 Provides counts of softirq handlers serviced since boot time, for each cpu.
760 > cat /proc/softirqs
761 CPU0 CPU1 CPU2 CPU3
762 HI: 0 0 0 0
763 TIMER: 27166 27120 27097 27034
764 NET_TX: 0 0 0 17
765 NET_RX: 42 0 0 39
766 BLOCK: 0 0 107 1121
767 TASKLET: 0 0 0 290
768 SCHED: 27035 26983 26971 26746
769 HRTIMER: 0 0 0 0
770 RCU: 1678 1769 2178 2250
773 1.3 IDE devices in /proc/ide
774 ----------------------------
776 The subdirectory /proc/ide contains information about all IDE devices of which
777 the kernel is aware. There is one subdirectory for each IDE controller, the
778 file drivers and a link for each IDE device, pointing to the device directory
779 in the controller specific subtree.
781 The file drivers contains general information about the drivers used for the
782 IDE devices:
784 > cat /proc/ide/drivers
785 ide-cdrom version 4.53
786 ide-disk version 1.08
788 More detailed information can be found in the controller specific
789 subdirectories. These are named ide0, ide1 and so on. Each of these
790 directories contains the files shown in table 1-6.
793 Table 1-6: IDE controller info in /proc/ide/ide?
794 ..............................................................................
795 File Content
796 channel IDE channel (0 or 1)
797 config Configuration (only for PCI/IDE bridge)
798 mate Mate name
799 model Type/Chipset of IDE controller
800 ..............................................................................
802 Each device connected to a controller has a separate subdirectory in the
803 controllers directory. The files listed in table 1-7 are contained in these
804 directories.
807 Table 1-7: IDE device information
808 ..............................................................................
809 File Content
810 cache The cache
811 capacity Capacity of the medium (in 512Byte blocks)
812 driver driver and version
813 geometry physical and logical geometry
814 identify device identify block
815 media media type
816 model device identifier
817 settings device setup
818 smart_thresholds IDE disk management thresholds
819 smart_values IDE disk management values
820 ..............................................................................
822 The most interesting file is settings. This file contains a nice overview of
823 the drive parameters:
825 # cat /proc/ide/ide0/hda/settings
826 name value min max mode
827 ---- ----- --- --- ----
828 bios_cyl 526 0 65535 rw
829 bios_head 255 0 255 rw
830 bios_sect 63 0 63 rw
831 breada_readahead 4 0 127 rw
832 bswap 0 0 1 r
833 file_readahead 72 0 2097151 rw
834 io_32bit 0 0 3 rw
835 keepsettings 0 0 1 rw
836 max_kb_per_request 122 1 127 rw
837 multcount 0 0 8 rw
838 nice1 1 0 1 rw
839 nowerr 0 0 1 rw
840 pio_mode write-only 0 255 w
841 slow 0 0 1 rw
842 unmaskirq 0 0 1 rw
843 using_dma 0 0 1 rw
846 1.4 Networking info in /proc/net
847 --------------------------------
849 The subdirectory /proc/net follows the usual pattern. Table 1-8 shows the
850 additional values you get for IP version 6 if you configure the kernel to
851 support this. Table 1-9 lists the files and their meaning.
854 Table 1-8: IPv6 info in /proc/net
855 ..............................................................................
856 File Content
857 udp6 UDP sockets (IPv6)
858 tcp6 TCP sockets (IPv6)
859 raw6 Raw device statistics (IPv6)
860 igmp6 IP multicast addresses, which this host joined (IPv6)
861 if_inet6 List of IPv6 interface addresses
862 ipv6_route Kernel routing table for IPv6
863 rt6_stats Global IPv6 routing tables statistics
864 sockstat6 Socket statistics (IPv6)
865 snmp6 Snmp data (IPv6)
866 ..............................................................................
869 Table 1-9: Network info in /proc/net
870 ..............................................................................
871 File Content
872 arp Kernel ARP table
873 dev network devices with statistics
874 dev_mcast the Layer2 multicast groups a device is listening too
875 (interface index, label, number of references, number of bound
876 addresses).
877 dev_stat network device status
878 ip_fwchains Firewall chain linkage
879 ip_fwnames Firewall chain names
880 ip_masq Directory containing the masquerading tables
881 ip_masquerade Major masquerading table
882 netstat Network statistics
883 raw raw device statistics
884 route Kernel routing table
885 rpc Directory containing rpc info
886 rt_cache Routing cache
887 snmp SNMP data
888 sockstat Socket statistics
889 tcp TCP sockets
890 tr_rif Token ring RIF routing table
891 udp UDP sockets
892 unix UNIX domain sockets
893 wireless Wireless interface data (Wavelan etc)
894 igmp IP multicast addresses, which this host joined
895 psched Global packet scheduler parameters.
896 netlink List of PF_NETLINK sockets
897 ip_mr_vifs List of multicast virtual interfaces
898 ip_mr_cache List of multicast routing cache
899 ..............................................................................
901 You can use this information to see which network devices are available in
902 your system and how much traffic was routed over those devices:
904 > cat /proc/net/dev
905 Inter-|Receive |[...
906 face |bytes packets errs drop fifo frame compressed multicast|[...
907 lo: 908188 5596 0 0 0 0 0 0 [...
908 ppp0:15475140 20721 410 0 0 410 0 0 [...
909 eth0: 614530 7085 0 0 0 0 0 1 [...
911 ...] Transmit
912 ...] bytes packets errs drop fifo colls carrier compressed
913 ...] 908188 5596 0 0 0 0 0 0
914 ...] 1375103 17405 0 0 0 0 0 0
915 ...] 1703981 5535 0 0 0 3 0 0
917 In addition, each Channel Bond interface has it's own directory. For
918 example, the bond0 device will have a directory called /proc/net/bond0/.
919 It will contain information that is specific to that bond, such as the
920 current slaves of the bond, the link status of the slaves, and how
921 many times the slaves link has failed.
923 1.5 SCSI info
924 -------------
926 If you have a SCSI host adapter in your system, you'll find a subdirectory
927 named after the driver for this adapter in /proc/scsi. You'll also see a list
928 of all recognized SCSI devices in /proc/scsi:
930 >cat /proc/scsi/scsi
931 Attached devices:
932 Host: scsi0 Channel: 00 Id: 00 Lun: 00
933 Vendor: IBM Model: DGHS09U Rev: 03E0
934 Type: Direct-Access ANSI SCSI revision: 03
935 Host: scsi0 Channel: 00 Id: 06 Lun: 00
936 Vendor: PIONEER Model: CD-ROM DR-U06S Rev: 1.04
937 Type: CD-ROM ANSI SCSI revision: 02
940 The directory named after the driver has one file for each adapter found in
941 the system. These files contain information about the controller, including
942 the used IRQ and the IO address range. The amount of information shown is
943 dependent on the adapter you use. The example shows the output for an Adaptec
944 AHA-2940 SCSI adapter:
946 > cat /proc/scsi/aic7xxx/0
948 Adaptec AIC7xxx driver version: 5.1.19/3.2.4
949 Compile Options:
950 TCQ Enabled By Default : Disabled
951 AIC7XXX_PROC_STATS : Disabled
952 AIC7XXX_RESET_DELAY : 5
953 Adapter Configuration:
954 SCSI Adapter: Adaptec AHA-294X Ultra SCSI host adapter
955 Ultra Wide Controller
956 PCI MMAPed I/O Base: 0xeb001000
957 Adapter SEEPROM Config: SEEPROM found and used.
958 Adaptec SCSI BIOS: Enabled
959 IRQ: 10
960 SCBs: Active 0, Max Active 2,
961 Allocated 15, HW 16, Page 255
962 Interrupts: 160328
963 BIOS Control Word: 0x18b6
964 Adapter Control Word: 0x005b
965 Extended Translation: Enabled
966 Disconnect Enable Flags: 0xffff
967 Ultra Enable Flags: 0x0001
968 Tag Queue Enable Flags: 0x0000
969 Ordered Queue Tag Flags: 0x0000
970 Default Tag Queue Depth: 8
971 Tagged Queue By Device array for aic7xxx host instance 0:
972 {255,255,255,255,255,255,255,255,255,255,255,255,255,255,255,255}
973 Actual queue depth per device for aic7xxx host instance 0:
974 {1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1}
975 Statistics:
976 (scsi0:0:0:0)
977 Device using Wide/Sync transfers at 40.0 MByte/sec, offset 8
978 Transinfo settings: current(12/8/1/0), goal(12/8/1/0), user(12/15/1/0)
979 Total transfers 160151 (74577 reads and 85574 writes)
980 (scsi0:0:6:0)
981 Device using Narrow/Sync transfers at 5.0 MByte/sec, offset 15
982 Transinfo settings: current(50/15/0/0), goal(50/15/0/0), user(50/15/0/0)
983 Total transfers 0 (0 reads and 0 writes)
986 1.6 Parallel port info in /proc/parport
987 ---------------------------------------
989 The directory /proc/parport contains information about the parallel ports of
990 your system. It has one subdirectory for each port, named after the port
991 number (0,1,2,...).
993 These directories contain the four files shown in Table 1-10.
996 Table 1-10: Files in /proc/parport
997 ..............................................................................
998 File Content
999 autoprobe Any IEEE-1284 device ID information that has been acquired.
1000 devices list of the device drivers using that port. A + will appear by the
1001 name of the device currently using the port (it might not appear
1002 against any).
1003 hardware Parallel port's base address, IRQ line and DMA channel.
1004 irq IRQ that parport is using for that port. This is in a separate
1005 file to allow you to alter it by writing a new value in (IRQ
1006 number or none).
1007 ..............................................................................
1009 1.7 TTY info in /proc/tty
1010 -------------------------
1012 Information about the available and actually used tty's can be found in the
1013 directory /proc/tty.You'll find entries for drivers and line disciplines in
1014 this directory, as shown in Table 1-11.
1017 Table 1-11: Files in /proc/tty
1018 ..............................................................................
1019 File Content
1020 drivers list of drivers and their usage
1021 ldiscs registered line disciplines
1022 driver/serial usage statistic and status of single tty lines
1023 ..............................................................................
1025 To see which tty's are currently in use, you can simply look into the file
1026 /proc/tty/drivers:
1028 > cat /proc/tty/drivers
1029 pty_slave /dev/pts 136 0-255 pty:slave
1030 pty_master /dev/ptm 128 0-255 pty:master
1031 pty_slave /dev/ttyp 3 0-255 pty:slave
1032 pty_master /dev/pty 2 0-255 pty:master
1033 serial /dev/cua 5 64-67 serial:callout
1034 serial /dev/ttyS 4 64-67 serial
1035 /dev/tty0 /dev/tty0 4 0 system:vtmaster
1036 /dev/ptmx /dev/ptmx 5 2 system
1037 /dev/console /dev/console 5 1 system:console
1038 /dev/tty /dev/tty 5 0 system:/dev/tty
1039 unknown /dev/tty 4 1-63 console
1042 1.8 Miscellaneous kernel statistics in /proc/stat
1043 -------------------------------------------------
1045 Various pieces of information about kernel activity are available in the
1046 /proc/stat file. All of the numbers reported in this file are aggregates
1047 since the system first booted. For a quick look, simply cat the file:
1049 > cat /proc/stat
1050 cpu 2255 34 2290 22625563 6290 127 456 0 0
1051 cpu0 1132 34 1441 11311718 3675 127 438 0 0
1052 cpu1 1123 0 849 11313845 2614 0 18 0 0
1053 intr 114930548 113199788 3 0 5 263 0 4 [... lots more numbers ...]
1054 ctxt 1990473
1055 btime 1062191376
1056 processes 2915
1057 procs_running 1
1058 procs_blocked 0
1059 softirq 183433 0 21755 12 39 1137 231 21459 2263
1061 The very first "cpu" line aggregates the numbers in all of the other "cpuN"
1062 lines. These numbers identify the amount of time the CPU has spent performing
1063 different kinds of work. Time units are in USER_HZ (typically hundredths of a
1064 second). The meanings of the columns are as follows, from left to right:
1066 - user: normal processes executing in user mode
1067 - nice: niced processes executing in user mode
1068 - system: processes executing in kernel mode
1069 - idle: twiddling thumbs
1070 - iowait: waiting for I/O to complete
1071 - irq: servicing interrupts
1072 - softirq: servicing softirqs
1073 - steal: involuntary wait
1074 - guest: running a normal guest
1075 - guest_nice: running a niced guest
1077 The "intr" line gives counts of interrupts serviced since boot time, for each
1078 of the possible system interrupts. The first column is the total of all
1079 interrupts serviced; each subsequent column is the total for that particular
1080 interrupt.
1082 The "ctxt" line gives the total number of context switches across all CPUs.
1084 The "btime" line gives the time at which the system booted, in seconds since
1085 the Unix epoch.
1087 The "processes" line gives the number of processes and threads created, which
1088 includes (but is not limited to) those created by calls to the fork() and
1089 clone() system calls.
1091 The "procs_running" line gives the total number of threads that are
1092 running or ready to run (i.e., the total number of runnable threads).
1094 The "procs_blocked" line gives the number of processes currently blocked,
1095 waiting for I/O to complete.
1097 The "softirq" line gives counts of softirqs serviced since boot time, for each
1098 of the possible system softirqs. The first column is the total of all
1099 softirqs serviced; each subsequent column is the total for that particular
1100 softirq.
1103 1.9 Ext4 file system parameters
1104 ------------------------------
1106 Information about mounted ext4 file systems can be found in
1107 /proc/fs/ext4. Each mounted filesystem will have a directory in
1108 /proc/fs/ext4 based on its device name (i.e., /proc/fs/ext4/hdc or
1109 /proc/fs/ext4/dm-0). The files in each per-device directory are shown
1110 in Table 1-12, below.
1112 Table 1-12: Files in /proc/fs/ext4/<devname>
1113 ..............................................................................
1114 File Content
1115 mb_groups details of multiblock allocator buddy cache of free blocks
1116 ..............................................................................
1119 ------------------------------------------------------------------------------
1120 Summary
1121 ------------------------------------------------------------------------------
1122 The /proc file system serves information about the running system. It not only
1123 allows access to process data but also allows you to request the kernel status
1124 by reading files in the hierarchy.
1126 The directory structure of /proc reflects the types of information and makes
1127 it easy, if not obvious, where to look for specific data.
1128 ------------------------------------------------------------------------------
1130 ------------------------------------------------------------------------------
1131 CHAPTER 2: MODIFYING SYSTEM PARAMETERS
1132 ------------------------------------------------------------------------------
1134 ------------------------------------------------------------------------------
1135 In This Chapter
1136 ------------------------------------------------------------------------------
1137 * Modifying kernel parameters by writing into files found in /proc/sys
1138 * Exploring the files which modify certain parameters
1139 * Review of the /proc/sys file tree
1140 ------------------------------------------------------------------------------
1143 A very interesting part of /proc is the directory /proc/sys. This is not only
1144 a source of information, it also allows you to change parameters within the
1145 kernel. Be very careful when attempting this. You can optimize your system,
1146 but you can also cause it to crash. Never alter kernel parameters on a
1147 production system. Set up a development machine and test to make sure that
1148 everything works the way you want it to. You may have no alternative but to
1149 reboot the machine once an error has been made.
1151 To change a value, simply echo the new value into the file. An example is
1152 given below in the section on the file system data. You need to be root to do
1153 this. You can create your own boot script to perform this every time your
1154 system boots.
1156 The files in /proc/sys can be used to fine tune and monitor miscellaneous and
1157 general things in the operation of the Linux kernel. Since some of the files
1158 can inadvertently disrupt your system, it is advisable to read both
1159 documentation and source before actually making adjustments. In any case, be
1160 very careful when writing to any of these files. The entries in /proc may
1161 change slightly between the 2.1.* and the 2.2 kernel, so if there is any doubt
1162 review the kernel documentation in the directory /usr/src/linux/Documentation.
1163 This chapter is heavily based on the documentation included in the pre 2.2
1164 kernels, and became part of it in version 2.2.1 of the Linux kernel.
1166 Please see: Documentation/sysctls/ directory for descriptions of these
1167 entries.
1169 ------------------------------------------------------------------------------
1170 Summary
1171 ------------------------------------------------------------------------------
1172 Certain aspects of kernel behavior can be modified at runtime, without the
1173 need to recompile the kernel, or even to reboot the system. The files in the
1174 /proc/sys tree can not only be read, but also modified. You can use the echo
1175 command to write value into these files, thereby changing the default settings
1176 of the kernel.
1177 ------------------------------------------------------------------------------
1179 ------------------------------------------------------------------------------
1180 CHAPTER 3: PER-PROCESS PARAMETERS
1181 ------------------------------------------------------------------------------
1183 3.1 /proc/<pid>/oom_adj - Adjust the oom-killer score
1184 ------------------------------------------------------
1186 This file can be used to adjust the score used to select which processes
1187 should be killed in an out-of-memory situation. Giving it a high score will
1188 increase the likelihood of this process being killed by the oom-killer. Valid
1189 values are in the range -16 to +15, plus the special value -17, which disables
1190 oom-killing altogether for this process.
1192 The process to be killed in an out-of-memory situation is selected among all others
1193 based on its badness score. This value equals the original memory size of the process
1194 and is then updated according to its CPU time (utime + stime) and the
1195 run time (uptime - start time). The longer it runs the smaller is the score.
1196 Badness score is divided by the square root of the CPU time and then by
1197 the double square root of the run time.
1199 Swapped out tasks are killed first. Half of each child's memory size is added to
1200 the parent's score if they do not share the same memory. Thus forking servers
1201 are the prime candidates to be killed. Having only one 'hungry' child will make
1202 parent less preferable than the child.
1204 /proc/<pid>/oom_score shows process' current badness score.
1206 The following heuristics are then applied:
1207 * if the task was reniced, its score doubles
1208 * superuser or direct hardware access tasks (CAP_SYS_ADMIN, CAP_SYS_RESOURCE
1209 or CAP_SYS_RAWIO) have their score divided by 4
1210 * if oom condition happened in one cpuset and checked process does not belong
1211 to it, its score is divided by 8
1212 * the resulting score is multiplied by two to the power of oom_adj, i.e.
1213 points <<= oom_adj when it is positive and
1214 points >>= -(oom_adj) otherwise
1216 The task with the highest badness score is then selected and its children
1217 are killed, process itself will be killed in an OOM situation when it does
1218 not have children or some of them disabled oom like described above.
1220 3.2 /proc/<pid>/oom_score - Display current oom-killer score
1221 -------------------------------------------------------------
1223 This file can be used to check the current score used by the oom-killer is for
1224 any given <pid>. Use it together with /proc/<pid>/oom_adj to tune which
1225 process should be killed in an out-of-memory situation.
1228 3.3 /proc/<pid>/io - Display the IO accounting fields
1229 -------------------------------------------------------
1231 This file contains IO statistics for each running process
1233 Example
1234 -------
1236 test:/tmp # dd if=/dev/zero of=/tmp/test.dat &
1237 [1] 3828
1239 test:/tmp # cat /proc/3828/io
1240 rchar: 323934931
1241 wchar: 323929600
1242 syscr: 632687
1243 syscw: 632675
1244 read_bytes: 0
1245 write_bytes: 323932160
1246 cancelled_write_bytes: 0
1249 Description
1250 -----------
1252 rchar
1253 -----
1255 I/O counter: chars read
1256 The number of bytes which this task has caused to be read from storage. This
1257 is simply the sum of bytes which this process passed to read() and pread().
1258 It includes things like tty IO and it is unaffected by whether or not actual
1259 physical disk IO was required (the read might have been satisfied from
1260 pagecache)
1263 wchar
1264 -----
1266 I/O counter: chars written
1267 The number of bytes which this task has caused, or shall cause to be written
1268 to disk. Similar caveats apply here as with rchar.
1271 syscr
1272 -----
1274 I/O counter: read syscalls
1275 Attempt to count the number of read I/O operations, i.e. syscalls like read()
1276 and pread().
1279 syscw
1280 -----
1282 I/O counter: write syscalls
1283 Attempt to count the number of write I/O operations, i.e. syscalls like
1284 write() and pwrite().
1287 read_bytes
1288 ----------
1290 I/O counter: bytes read
1291 Attempt to count the number of bytes which this process really did cause to
1292 be fetched from the storage layer. Done at the submit_bio() level, so it is
1293 accurate for block-backed filesystems. <please add status regarding NFS and
1294 CIFS at a later time>
1297 write_bytes
1298 -----------
1300 I/O counter: bytes written
1301 Attempt to count the number of bytes which this process caused to be sent to
1302 the storage layer. This is done at page-dirtying time.
1305 cancelled_write_bytes
1306 ---------------------
1308 The big inaccuracy here is truncate. If a process writes 1MB to a file and
1309 then deletes the file, it will in fact perform no writeout. But it will have
1310 been accounted as having caused 1MB of write.
1311 In other words: The number of bytes which this process caused to not happen,
1312 by truncating pagecache. A task can cause "negative" IO too. If this task
1313 truncates some dirty pagecache, some IO which another task has been accounted
1314 for (in it's write_bytes) will not be happening. We _could_ just subtract that
1315 from the truncating task's write_bytes, but there is information loss in doing
1316 that.
1319 Note
1320 ----
1322 At its current implementation state, this is a bit racy on 32-bit machines: if
1323 process A reads process B's /proc/pid/io while process B is updating one of
1324 those 64-bit counters, process A could see an intermediate result.
1327 More information about this can be found within the taskstats documentation in
1328 Documentation/accounting.
1330 3.4 /proc/<pid>/coredump_filter - Core dump filtering settings
1331 ---------------------------------------------------------------
1332 When a process is dumped, all anonymous memory is written to a core file as
1333 long as the size of the core file isn't limited. But sometimes we don't want
1334 to dump some memory segments, for example, huge shared memory. Conversely,
1335 sometimes we want to save file-backed memory segments into a core file, not
1336 only the individual files.
1338 /proc/<pid>/coredump_filter allows you to customize which memory segments
1339 will be dumped when the <pid> process is dumped. coredump_filter is a bitmask
1340 of memory types. If a bit of the bitmask is set, memory segments of the
1341 corresponding memory type are dumped, otherwise they are not dumped.
1343 The following 7 memory types are supported:
1344 - (bit 0) anonymous private memory
1345 - (bit 1) anonymous shared memory
1346 - (bit 2) file-backed private memory
1347 - (bit 3) file-backed shared memory
1348 - (bit 4) ELF header pages in file-backed private memory areas (it is
1349 effective only if the bit 2 is cleared)
1350 - (bit 5) hugetlb private memory
1351 - (bit 6) hugetlb shared memory
1353 Note that MMIO pages such as frame buffer are never dumped and vDSO pages
1354 are always dumped regardless of the bitmask status.
1356 Note bit 0-4 doesn't effect any hugetlb memory. hugetlb memory are only
1357 effected by bit 5-6.
1359 Default value of coredump_filter is 0x23; this means all anonymous memory
1360 segments and hugetlb private memory are dumped.
1362 If you don't want to dump all shared memory segments attached to pid 1234,
1363 write 0x21 to the process's proc file.
1365 $ echo 0x21 > /proc/1234/coredump_filter
1367 When a new process is created, the process inherits the bitmask status from its
1368 parent. It is useful to set up coredump_filter before the program runs.
1369 For example:
1371 $ echo 0x7 > /proc/self/coredump_filter
1372 $ ./some_program
1374 3.5 /proc/<pid>/mountinfo - Information about mounts
1375 --------------------------------------------------------
1377 This file contains lines of the form:
1379 36 35 98:0 /mnt1 /mnt2 rw,noatime master:1 - ext3 /dev/root rw,errors=continue
1380 (1)(2)(3) (4) (5) (6) (7) (8) (9) (10) (11)
1382 (1) mount ID: unique identifier of the mount (may be reused after umount)
1383 (2) parent ID: ID of parent (or of self for the top of the mount tree)
1384 (3) major:minor: value of st_dev for files on filesystem
1385 (4) root: root of the mount within the filesystem
1386 (5) mount point: mount point relative to the process's root
1387 (6) mount options: per mount options
1388 (7) optional fields: zero or more fields of the form "tag[:value]"
1389 (8) separator: marks the end of the optional fields
1390 (9) filesystem type: name of filesystem of the form "type[.subtype]"
1391 (10) mount source: filesystem specific information or "none"
1392 (11) super options: per super block options
1394 Parsers should ignore all unrecognised optional fields. Currently the
1395 possible optional fields are:
1397 shared:X mount is shared in peer group X
1398 master:X mount is slave to peer group X
1399 propagate_from:X mount is slave and receives propagation from peer group X (*)
1400 unbindable mount is unbindable
1402 (*) X is the closest dominant peer group under the process's root. If
1403 X is the immediate master of the mount, or if there's no dominant peer
1404 group under the same root, then only the "master:X" field is present
1405 and not the "propagate_from:X" field.
1407 For more information on mount propagation see:
1409 Documentation/filesystems/sharedsubtree.txt
1412 3.6 /proc/<pid>/comm & /proc/<pid>/task/<tid>/comm
1413 --------------------------------------------------------
1414 These files provide a method to access a tasks comm value. It also allows for
1415 a task to set its own or one of its thread siblings comm value. The comm value
1416 is limited in size compared to the cmdline value, so writing anything longer
1417 then the kernel's TASK_COMM_LEN (currently 16 chars) will result in a truncated
1418 comm value.