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1------------------------------------------------------------------------------
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>
6
72.4.x update Jorge Nerin <comandante@zaralinux.com> November 14 2000
8move /proc/sys Shen Feng <shen@cn.fujitsu.com> April 1 2009
9------------------------------------------------------------------------------
10Version 1.3 Kernel version 2.2.12
11 Kernel version 2.4.0-test11-pre4
12------------------------------------------------------------------------------
13fixes/update part 1.1 Stefani Seibold <stefani@seibold.net> June 9 2009
14
15Table of Contents
16-----------------
17
18 0 Preface
19 0.1 Introduction/Credits
20 0.2 Legal Stuff
21
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
32
33 2 Modifying System Parameters
34
35 3 Per-Process Parameters
36 3.1 /proc/<pid>/oom_adj & /proc/<pid>/oom_score_adj - Adjust the oom-killer
37 score
38 3.2 /proc/<pid>/oom_score - Display current oom-killer score
39 3.3 /proc/<pid>/io - Display the IO accounting fields
40 3.4 /proc/<pid>/coredump_filter - Core dump filtering settings
41 3.5 /proc/<pid>/mountinfo - Information about mounts
42 3.6 /proc/<pid>/comm & /proc/<pid>/task/<tid>/comm
43
44
45------------------------------------------------------------------------------
46Preface
47------------------------------------------------------------------------------
48
490.1 Introduction/Credits
50------------------------
51
52This documentation is part of a soon (or so we hope) to be released book on
53the SuSE Linux distribution. As there is no complete documentation for the
54/proc file system and we've used many freely available sources to write these
55chapters, it seems only fair to give the work back to the Linux community.
56This work is based on the 2.2.* kernel version and the upcoming 2.4.*. I'm
57afraid it's still far from complete, but we hope it will be useful. As far as
58we know, it is the first 'all-in-one' document about the /proc file system. It
59is focused on the Intel x86 hardware, so if you are looking for PPC, ARM,
60SPARC, AXP, etc., features, you probably won't find what you are looking for.
61It also only covers IPv4 networking, not IPv6 nor other protocols - sorry. But
62additions and patches are welcome and will be added to this document if you
63mail them to Bodo.
64
65We'd like to thank Alan Cox, Rik van Riel, and Alexey Kuznetsov and a lot of
66other people for help compiling this documentation. We'd also like to extend a
67special thank you to Andi Kleen for documentation, which we relied on heavily
68to create this document, as well as the additional information he provided.
69Thanks to everybody else who contributed source or docs to the Linux kernel
70and helped create a great piece of software... :)
71
72If you have any comments, corrections or additions, please don't hesitate to
73contact Bodo Bauer at bb@ricochet.net. We'll be happy to add them to this
74document.
75
76The latest version of this document is available online at
77http://tldp.org/LDP/Linux-Filesystem-Hierarchy/html/proc.html
78
79If the above direction does not works for you, you could try the kernel
80mailing list at linux-kernel@vger.kernel.org and/or try to reach me at
81comandante@zaralinux.com.
82
830.2 Legal Stuff
84---------------
85
86We don't guarantee the correctness of this document, and if you come to us
87complaining about how you screwed up your system because of incorrect
88documentation, we won't feel responsible...
89
90------------------------------------------------------------------------------
91CHAPTER 1: COLLECTING SYSTEM INFORMATION
92------------------------------------------------------------------------------
93
94------------------------------------------------------------------------------
95In This Chapter
96------------------------------------------------------------------------------
97* Investigating the properties of the pseudo file system /proc and its
98 ability to provide information on the running Linux system
99* Examining /proc's structure
100* Uncovering various information about the kernel and the processes running
101 on the system
102------------------------------------------------------------------------------
103
104
105The proc file system acts as an interface to internal data structures in the
106kernel. It can be used to obtain information about the system and to change
107certain kernel parameters at runtime (sysctl).
108
109First, we'll take a look at the read-only parts of /proc. In Chapter 2, we
110show you how you can use /proc/sys to change settings.
111
1121.1 Process-Specific Subdirectories
113-----------------------------------
114
115The directory /proc contains (among other things) one subdirectory for each
116process running on the system, which is named after the process ID (PID).
117
118The link self points to the process reading the file system. Each process
119subdirectory has the entries listed in Table 1-1.
120
121
122Table 1-1: Process specific entries in /proc
123..............................................................................
124 File Content
125 clear_refs Clears page referenced bits shown in smaps output
126 cmdline Command line arguments
127 cpu Current and last cpu in which it was executed (2.4)(smp)
128 cwd Link to the current working directory
129 environ Values of environment variables
130 exe Link to the executable of this process
131 fd Directory, which contains all file descriptors
132 maps Memory maps to executables and library files (2.4)
133 mem Memory held by this process
134 root Link to the root directory of this process
135 stat Process status
136 statm Process memory status information
137 status Process status in human readable form
138 wchan If CONFIG_KALLSYMS is set, a pre-decoded wchan
139 pagemap Page table
140 stack Report full stack trace, enable via CONFIG_STACKTRACE
141 smaps a extension based on maps, showing the memory consumption of
142 each mapping
143..............................................................................
144
145For example, to get the status information of a process, all you have to do is
146read the file /proc/PID/status:
147
148 >cat /proc/self/status
149 Name: cat
150 State: R (running)
151 Tgid: 5452
152 Pid: 5452
153 PPid: 743
154 TracerPid: 0 (2.4)
155 Uid: 501 501 501 501
156 Gid: 100 100 100 100
157 FDSize: 256
158 Groups: 100 14 16
159 VmPeak: 5004 kB
160 VmSize: 5004 kB
161 VmLck: 0 kB
162 VmHWM: 476 kB
163 VmRSS: 476 kB
164 VmData: 156 kB
165 VmStk: 88 kB
166 VmExe: 68 kB
167 VmLib: 1412 kB
168 VmPTE: 20 kb
169 VmSwap: 0 kB
170 Threads: 1
171 SigQ: 0/28578
172 SigPnd: 0000000000000000
173 ShdPnd: 0000000000000000
174 SigBlk: 0000000000000000
175 SigIgn: 0000000000000000
176 SigCgt: 0000000000000000
177 CapInh: 00000000fffffeff
178 CapPrm: 0000000000000000
179 CapEff: 0000000000000000
180 CapBnd: ffffffffffffffff
181 voluntary_ctxt_switches: 0
182 nonvoluntary_ctxt_switches: 1
183
184This shows you nearly the same information you would get if you viewed it with
185the ps command. In fact, ps uses the proc file system to obtain its
186information. But you get a more detailed view of the process by reading the
187file /proc/PID/status. It fields are described in table 1-2.
188
189The statm file contains more detailed information about the process
190memory usage. Its seven fields are explained in Table 1-3. The stat file
191contains details information about the process itself. Its fields are
192explained in Table 1-4.
193
194(for SMP CONFIG users)
195For making accounting scalable, RSS related information are handled in
196asynchronous manner and the vaule may not be very precise. To see a precise
197snapshot of a moment, you can see /proc/<pid>/smaps file and scan page table.
198It's slow but very precise.
199
200Table 1-2: Contents of the status files (as of 2.6.30-rc7)
201..............................................................................
202 Field Content
203 Name filename of the executable
204 State state (R is running, S is sleeping, D is sleeping
205 in an uninterruptible wait, Z is zombie,
206 T is traced or stopped)
207 Tgid thread group ID
208 Pid process id
209 PPid process id of the parent process
210 TracerPid PID of process tracing this process (0 if not)
211 Uid Real, effective, saved set, and file system UIDs
212 Gid Real, effective, saved set, and file system GIDs
213 FDSize number of file descriptor slots currently allocated
214 Groups supplementary group list
215 VmPeak peak virtual memory size
216 VmSize total program size
217 VmLck locked memory size
218 VmHWM peak resident set size ("high water mark")
219 VmRSS size of memory portions
220 VmData size of data, stack, and text segments
221 VmStk size of data, stack, and text segments
222 VmExe size of text segment
223 VmLib size of shared library code
224 VmPTE size of page table entries
225 VmSwap size of swap usage (the number of referred swapents)
226 Threads number of threads
227 SigQ number of signals queued/max. number for queue
228 SigPnd bitmap of pending signals for the thread
229 ShdPnd bitmap of shared pending signals for the process
230 SigBlk bitmap of blocked signals
231 SigIgn bitmap of ignored signals
232 SigCgt bitmap of catched signals
233 CapInh bitmap of inheritable capabilities
234 CapPrm bitmap of permitted capabilities
235 CapEff bitmap of effective capabilities
236 CapBnd bitmap of capabilities bounding set
237 Cpus_allowed mask of CPUs on which this process may run
238 Cpus_allowed_list Same as previous, but in "list format"
239 Mems_allowed mask of memory nodes allowed to this process
240 Mems_allowed_list Same as previous, but in "list format"
241 voluntary_ctxt_switches number of voluntary context switches
242 nonvoluntary_ctxt_switches number of non voluntary context switches
243..............................................................................
244
245Table 1-3: Contents of the statm files (as of 2.6.8-rc3)
246..............................................................................
247 Field Content
248 size total program size (pages) (same as VmSize in status)
249 resident size of memory portions (pages) (same as VmRSS in status)
250 shared number of pages that are shared (i.e. backed by a file)
251 trs number of pages that are 'code' (not including libs; broken,
252 includes data segment)
253 lrs number of pages of library (always 0 on 2.6)
254 drs number of pages of data/stack (including libs; broken,
255 includes library text)
256 dt number of dirty pages (always 0 on 2.6)
257..............................................................................
258
259
260Table 1-4: Contents of the stat files (as of 2.6.30-rc7)
261..............................................................................
262 Field Content
263 pid process id
264 tcomm filename of the executable
265 state state (R is running, S is sleeping, D is sleeping in an
266 uninterruptible wait, Z is zombie, T is traced or stopped)
267 ppid process id of the parent process
268 pgrp pgrp of the process
269 sid session id
270 tty_nr tty the process uses
271 tty_pgrp pgrp of the tty
272 flags task flags
273 min_flt number of minor faults
274 cmin_flt number of minor faults with child's
275 maj_flt number of major faults
276 cmaj_flt number of major faults with child's
277 utime user mode jiffies
278 stime kernel mode jiffies
279 cutime user mode jiffies with child's
280 cstime kernel mode jiffies with child's
281 priority priority level
282 nice nice level
283 num_threads number of threads
284 it_real_value (obsolete, always 0)
285 start_time time the process started after system boot
286 vsize virtual memory size
287 rss resident set memory size
288 rsslim current limit in bytes on the rss
289 start_code address above which program text can run
290 end_code address below which program text can run
291 start_stack address of the start of the stack
292 esp current value of ESP
293 eip current value of EIP
294 pending bitmap of pending signals
295 blocked bitmap of blocked signals
296 sigign bitmap of ignored signals
297 sigcatch bitmap of catched signals
298 wchan address where process went to sleep
299 0 (place holder)
300 0 (place holder)
301 exit_signal signal to send to parent thread on exit
302 task_cpu which CPU the task is scheduled on
303 rt_priority realtime priority
304 policy scheduling policy (man sched_setscheduler)
305 blkio_ticks time spent waiting for block IO
306 gtime guest time of the task in jiffies
307 cgtime guest time of the task children in jiffies
308..............................................................................
309
310The /proc/PID/maps file containing the currently mapped memory regions and
311their access permissions.
312
313The format is:
314
315address perms offset dev inode pathname
316
31708048000-08049000 r-xp 00000000 03:00 8312 /opt/test
31808049000-0804a000 rw-p 00001000 03:00 8312 /opt/test
3190804a000-0806b000 rw-p 00000000 00:00 0 [heap]
320a7cb1000-a7cb2000 ---p 00000000 00:00 0
321a7cb2000-a7eb2000 rw-p 00000000 00:00 0
322a7eb2000-a7eb3000 ---p 00000000 00:00 0
323a7eb3000-a7ed5000 rw-p 00000000 00:00 0
324a7ed5000-a8008000 r-xp 00000000 03:00 4222 /lib/libc.so.6
325a8008000-a800a000 r--p 00133000 03:00 4222 /lib/libc.so.6
326a800a000-a800b000 rw-p 00135000 03:00 4222 /lib/libc.so.6
327a800b000-a800e000 rw-p 00000000 00:00 0
328a800e000-a8022000 r-xp 00000000 03:00 14462 /lib/libpthread.so.0
329a8022000-a8023000 r--p 00013000 03:00 14462 /lib/libpthread.so.0
330a8023000-a8024000 rw-p 00014000 03:00 14462 /lib/libpthread.so.0
331a8024000-a8027000 rw-p 00000000 00:00 0
332a8027000-a8043000 r-xp 00000000 03:00 8317 /lib/ld-linux.so.2
333a8043000-a8044000 r--p 0001b000 03:00 8317 /lib/ld-linux.so.2
334a8044000-a8045000 rw-p 0001c000 03:00 8317 /lib/ld-linux.so.2
335aff35000-aff4a000 rw-p 00000000 00:00 0 [stack]
336ffffe000-fffff000 r-xp 00000000 00:00 0 [vdso]
337
338where "address" is the address space in the process that it occupies, "perms"
339is a set of permissions:
340
341 r = read
342 w = write
343 x = execute
344 s = shared
345 p = private (copy on write)
346
347"offset" is the offset into the mapping, "dev" is the device (major:minor), and
348"inode" is the inode on that device. 0 indicates that no inode is associated
349with the memory region, as the case would be with BSS (uninitialized data).
350The "pathname" shows the name associated file for this mapping. If the mapping
351is not associated with a file:
352
353 [heap] = the heap of the program
354 [stack] = the stack of the main process
355 [vdso] = the "virtual dynamic shared object",
356 the kernel system call handler
357
358 or if empty, the mapping is anonymous.
359
360
361The /proc/PID/smaps is an extension based on maps, showing the memory
362consumption for each of the process's mappings. For each of mappings there
363is a series of lines such as the following:
364
36508048000-080bc000 r-xp 00000000 03:02 13130 /bin/bash
366Size: 1084 kB
367Rss: 892 kB
368Pss: 374 kB
369Shared_Clean: 892 kB
370Shared_Dirty: 0 kB
371Private_Clean: 0 kB
372Private_Dirty: 0 kB
373Referenced: 892 kB
374Anonymous: 0 kB
375Swap: 0 kB
376KernelPageSize: 4 kB
377MMUPageSize: 4 kB
378Locked: 374 kB
379
380The first of these lines shows the same information as is displayed for the
381mapping in /proc/PID/maps. The remaining lines show the size of the mapping
382(size), the amount of the mapping that is currently resident in RAM (RSS), the
383process' proportional share of this mapping (PSS), the number of clean and
384dirty private pages in the mapping. Note that even a page which is part of a
385MAP_SHARED mapping, but has only a single pte mapped, i.e. is currently used
386by only one process, is accounted as private and not as shared. "Referenced"
387indicates the amount of memory currently marked as referenced or accessed.
388"Anonymous" shows the amount of memory that does not belong to any file. Even
389a mapping associated with a file may contain anonymous pages: when MAP_PRIVATE
390and a page is modified, the file page is replaced by a private anonymous copy.
391"Swap" shows how much would-be-anonymous memory is also used, but out on
392swap.
393
394This file is only present if the CONFIG_MMU kernel configuration option is
395enabled.
396
397The /proc/PID/clear_refs is used to reset the PG_Referenced and ACCESSED/YOUNG
398bits on both physical and virtual pages associated with a process.
399To clear the bits for all the pages associated with the process
400 > echo 1 > /proc/PID/clear_refs
401
402To clear the bits for the anonymous pages associated with the process
403 > echo 2 > /proc/PID/clear_refs
404
405To clear the bits for the file mapped pages associated with the process
406 > echo 3 > /proc/PID/clear_refs
407Any other value written to /proc/PID/clear_refs will have no effect.
408
409The /proc/pid/pagemap gives the PFN, which can be used to find the pageflags
410using /proc/kpageflags and number of times a page is mapped using
411/proc/kpagecount. For detailed explanation, see Documentation/vm/pagemap.txt.
412
4131.2 Kernel data
414---------------
415
416Similar to the process entries, the kernel data files give information about
417the running kernel. The files used to obtain this information are contained in
418/proc and are listed in Table 1-5. Not all of these will be present in your
419system. It depends on the kernel configuration and the loaded modules, which
420files are there, and which are missing.
421
422Table 1-5: Kernel info in /proc
423..............................................................................
424 File Content
425 apm Advanced power management info
426 buddyinfo Kernel memory allocator information (see text) (2.5)
427 bus Directory containing bus specific information
428 cmdline Kernel command line
429 cpuinfo Info about the CPU
430 devices Available devices (block and character)
431 dma Used DMS channels
432 filesystems Supported filesystems
433 driver Various drivers grouped here, currently rtc (2.4)
434 execdomains Execdomains, related to security (2.4)
435 fb Frame Buffer devices (2.4)
436 fs File system parameters, currently nfs/exports (2.4)
437 ide Directory containing info about the IDE subsystem
438 interrupts Interrupt usage
439 iomem Memory map (2.4)
440 ioports I/O port usage
441 irq Masks for irq to cpu affinity (2.4)(smp?)
442 isapnp ISA PnP (Plug&Play) Info (2.4)
443 kcore Kernel core image (can be ELF or A.OUT(deprecated in 2.4))
444 kmsg Kernel messages
445 ksyms Kernel symbol table
446 loadavg Load average of last 1, 5 & 15 minutes
447 locks Kernel locks
448 meminfo Memory info
449 misc Miscellaneous
450 modules List of loaded modules
451 mounts Mounted filesystems
452 net Networking info (see text)
453 pagetypeinfo Additional page allocator information (see text) (2.5)
454 partitions Table of partitions known to the system
455 pci Deprecated info of PCI bus (new way -> /proc/bus/pci/,
456 decoupled by lspci (2.4)
457 rtc Real time clock
458 scsi SCSI info (see text)
459 slabinfo Slab pool info
460 softirqs softirq usage
461 stat Overall statistics
462 swaps Swap space utilization
463 sys See chapter 2
464 sysvipc Info of SysVIPC Resources (msg, sem, shm) (2.4)
465 tty Info of tty drivers
466 uptime System uptime
467 version Kernel version
468 video bttv info of video resources (2.4)
469 vmallocinfo Show vmalloced areas
470..............................................................................
471
472You can, for example, check which interrupts are currently in use and what
473they are used for by looking in the file /proc/interrupts:
474
475 > cat /proc/interrupts
476 CPU0
477 0: 8728810 XT-PIC timer
478 1: 895 XT-PIC keyboard
479 2: 0 XT-PIC cascade
480 3: 531695 XT-PIC aha152x
481 4: 2014133 XT-PIC serial
482 5: 44401 XT-PIC pcnet_cs
483 8: 2 XT-PIC rtc
484 11: 8 XT-PIC i82365
485 12: 182918 XT-PIC PS/2 Mouse
486 13: 1 XT-PIC fpu
487 14: 1232265 XT-PIC ide0
488 15: 7 XT-PIC ide1
489 NMI: 0
490
491In 2.4.* a couple of lines where added to this file LOC & ERR (this time is the
492output of a SMP machine):
493
494 > cat /proc/interrupts
495
496 CPU0 CPU1
497 0: 1243498 1214548 IO-APIC-edge timer
498 1: 8949 8958 IO-APIC-edge keyboard
499 2: 0 0 XT-PIC cascade
500 5: 11286 10161 IO-APIC-edge soundblaster
501 8: 1 0 IO-APIC-edge rtc
502 9: 27422 27407 IO-APIC-edge 3c503
503 12: 113645 113873 IO-APIC-edge PS/2 Mouse
504 13: 0 0 XT-PIC fpu
505 14: 22491 24012 IO-APIC-edge ide0
506 15: 2183 2415 IO-APIC-edge ide1
507 17: 30564 30414 IO-APIC-level eth0
508 18: 177 164 IO-APIC-level bttv
509 NMI: 2457961 2457959
510 LOC: 2457882 2457881
511 ERR: 2155
512
513NMI is incremented in this case because every timer interrupt generates a NMI
514(Non Maskable Interrupt) which is used by the NMI Watchdog to detect lockups.
515
516LOC is the local interrupt counter of the internal APIC of every CPU.
517
518ERR is incremented in the case of errors in the IO-APIC bus (the bus that
519connects the CPUs in a SMP system. This means that an error has been detected,
520the IO-APIC automatically retry the transmission, so it should not be a big
521problem, but you should read the SMP-FAQ.
522
523In 2.6.2* /proc/interrupts was expanded again. This time the goal was for
524/proc/interrupts to display every IRQ vector in use by the system, not
525just those considered 'most important'. The new vectors are:
526
527 THR -- interrupt raised when a machine check threshold counter
528 (typically counting ECC corrected errors of memory or cache) exceeds
529 a configurable threshold. Only available on some systems.
530
531 TRM -- a thermal event interrupt occurs when a temperature threshold
532 has been exceeded for the CPU. This interrupt may also be generated
533 when the temperature drops back to normal.
534
535 SPU -- a spurious interrupt is some interrupt that was raised then lowered
536 by some IO device before it could be fully processed by the APIC. Hence
537 the APIC sees the interrupt but does not know what device it came from.
538 For this case the APIC will generate the interrupt with a IRQ vector
539 of 0xff. This might also be generated by chipset bugs.
540
541 RES, CAL, TLB -- rescheduling, call and TLB flush interrupts are
542 sent from one CPU to another per the needs of the OS. Typically,
543 their statistics are used by kernel developers and interested users to
544 determine the occurrence of interrupts of the given type.
545
546The above IRQ vectors are displayed only when relevant. For example,
547the threshold vector does not exist on x86_64 platforms. Others are
548suppressed when the system is a uniprocessor. As of this writing, only
549i386 and x86_64 platforms support the new IRQ vector displays.
550
551Of some interest is the introduction of the /proc/irq directory to 2.4.
552It could be used to set IRQ to CPU affinity, this means that you can "hook" an
553IRQ to only one CPU, or to exclude a CPU of handling IRQs. The contents of the
554irq subdir is one subdir for each IRQ, and two files; default_smp_affinity and
555prof_cpu_mask.
556
557For example
558 > ls /proc/irq/
559 0 10 12 14 16 18 2 4 6 8 prof_cpu_mask
560 1 11 13 15 17 19 3 5 7 9 default_smp_affinity
561 > ls /proc/irq/0/
562 smp_affinity
563
564smp_affinity is a bitmask, in which you can specify which CPUs can handle the
565IRQ, you can set it by doing:
566
567 > echo 1 > /proc/irq/10/smp_affinity
568
569This means that only the first CPU will handle the IRQ, but you can also echo
5705 which means that only the first and fourth CPU can handle the IRQ.
571
572The contents of each smp_affinity file is the same by default:
573
574 > cat /proc/irq/0/smp_affinity
575 ffffffff
576
577There is an alternate interface, smp_affinity_list which allows specifying
578a cpu range instead of a bitmask:
579
580 > cat /proc/irq/0/smp_affinity_list
581 1024-1031
582
583The default_smp_affinity mask applies to all non-active IRQs, which are the
584IRQs which have not yet been allocated/activated, and hence which lack a
585/proc/irq/[0-9]* directory.
586
587The node file on an SMP system shows the node to which the device using the IRQ
588reports itself as being attached. This hardware locality information does not
589include information about any possible driver locality preference.
590
591prof_cpu_mask specifies which CPUs are to be profiled by the system wide
592profiler. Default value is ffffffff (all cpus if there are only 32 of them).
593
594The way IRQs are routed is handled by the IO-APIC, and it's Round Robin
595between all the CPUs which are allowed to handle it. As usual the kernel has
596more info than you and does a better job than you, so the defaults are the
597best choice for almost everyone. [Note this applies only to those IO-APIC's
598that support "Round Robin" interrupt distribution.]
599
600There are three more important subdirectories in /proc: net, scsi, and sys.
601The general rule is that the contents, or even the existence of these
602directories, depend on your kernel configuration. If SCSI is not enabled, the
603directory scsi may not exist. The same is true with the net, which is there
604only when networking support is present in the running kernel.
605
606The slabinfo file gives information about memory usage at the slab level.
607Linux uses slab pools for memory management above page level in version 2.2.
608Commonly used objects have their own slab pool (such as network buffers,
609directory cache, and so on).
610
611..............................................................................
612
613> cat /proc/buddyinfo
614
615Node 0, zone DMA 0 4 5 4 4 3 ...
616Node 0, zone Normal 1 0 0 1 101 8 ...
617Node 0, zone HighMem 2 0 0 1 1 0 ...
618
619External fragmentation is a problem under some workloads, and buddyinfo is a
620useful tool for helping diagnose these problems. Buddyinfo will give you a
621clue as to how big an area you can safely allocate, or why a previous
622allocation failed.
623
624Each column represents the number of pages of a certain order which are
625available. In this case, there are 0 chunks of 2^0*PAGE_SIZE available in
626ZONE_DMA, 4 chunks of 2^1*PAGE_SIZE in ZONE_DMA, 101 chunks of 2^4*PAGE_SIZE
627available in ZONE_NORMAL, etc...
628
629More information relevant to external fragmentation can be found in
630pagetypeinfo.
631
632> cat /proc/pagetypeinfo
633Page block order: 9
634Pages per block: 512
635
636Free pages count per migrate type at order 0 1 2 3 4 5 6 7 8 9 10
637Node 0, zone DMA, type Unmovable 0 0 0 1 1 1 1 1 1 1 0
638Node 0, zone DMA, type Reclaimable 0 0 0 0 0 0 0 0 0 0 0
639Node 0, zone DMA, type Movable 1 1 2 1 2 1 1 0 1 0 2
640Node 0, zone DMA, type Reserve 0 0 0 0 0 0 0 0 0 1 0
641Node 0, zone DMA, type Isolate 0 0 0 0 0 0 0 0 0 0 0
642Node 0, zone DMA32, type Unmovable 103 54 77 1 1 1 11 8 7 1 9
643Node 0, zone DMA32, type Reclaimable 0 0 2 1 0 0 0 0 1 0 0
644Node 0, zone DMA32, type Movable 169 152 113 91 77 54 39 13 6 1 452
645Node 0, zone DMA32, type Reserve 1 2 2 2 2 0 1 1 1 1 0
646Node 0, zone DMA32, type Isolate 0 0 0 0 0 0 0 0 0 0 0
647
648Number of blocks type Unmovable Reclaimable Movable Reserve Isolate
649Node 0, zone DMA 2 0 5 1 0
650Node 0, zone DMA32 41 6 967 2 0
651
652Fragmentation avoidance in the kernel works by grouping pages of different
653migrate types into the same contiguous regions of memory called page blocks.
654A page block is typically the size of the default hugepage size e.g. 2MB on
655X86-64. By keeping pages grouped based on their ability to move, the kernel
656can reclaim pages within a page block to satisfy a high-order allocation.
657
658The pagetypinfo begins with information on the size of a page block. It
659then gives the same type of information as buddyinfo except broken down
660by migrate-type and finishes with details on how many page blocks of each
661type exist.
662
663If min_free_kbytes has been tuned correctly (recommendations made by hugeadm
664from libhugetlbfs http://sourceforge.net/projects/libhugetlbfs/), one can
665make an estimate of the likely number of huge pages that can be allocated
666at a given point in time. All the "Movable" blocks should be allocatable
667unless memory has been mlock()'d. Some of the Reclaimable blocks should
668also be allocatable although a lot of filesystem metadata may have to be
669reclaimed to achieve this.
670
671..............................................................................
672
673meminfo:
674
675Provides information about distribution and utilization of memory. This
676varies by architecture and compile options. The following is from a
67716GB PIII, which has highmem enabled. You may not have all of these fields.
678
679> cat /proc/meminfo
680
681The "Locked" indicates whether the mapping is locked in memory or not.
682
683
684MemTotal: 16344972 kB
685MemFree: 13634064 kB
686Buffers: 3656 kB
687Cached: 1195708 kB
688SwapCached: 0 kB
689Active: 891636 kB
690Inactive: 1077224 kB
691HighTotal: 15597528 kB
692HighFree: 13629632 kB
693LowTotal: 747444 kB
694LowFree: 4432 kB
695SwapTotal: 0 kB
696SwapFree: 0 kB
697Dirty: 968 kB
698Writeback: 0 kB
699AnonPages: 861800 kB
700Mapped: 280372 kB
701Slab: 284364 kB
702SReclaimable: 159856 kB
703SUnreclaim: 124508 kB
704PageTables: 24448 kB
705NFS_Unstable: 0 kB
706Bounce: 0 kB
707WritebackTmp: 0 kB
708CommitLimit: 7669796 kB
709Committed_AS: 100056 kB
710VmallocTotal: 112216 kB
711VmallocUsed: 428 kB
712VmallocChunk: 111088 kB
713
714 MemTotal: Total usable ram (i.e. physical ram minus a few reserved
715 bits and the kernel binary code)
716 MemFree: The sum of LowFree+HighFree
717 Buffers: Relatively temporary storage for raw disk blocks
718 shouldn't get tremendously large (20MB or so)
719 Cached: in-memory cache for files read from the disk (the
720 pagecache). Doesn't include SwapCached
721 SwapCached: Memory that once was swapped out, is swapped back in but
722 still also is in the swapfile (if memory is needed it
723 doesn't need to be swapped out AGAIN because it is already
724 in the swapfile. This saves I/O)
725 Active: Memory that has been used more recently and usually not
726 reclaimed unless absolutely necessary.
727 Inactive: Memory which has been less recently used. It is more
728 eligible to be reclaimed for other purposes
729 HighTotal:
730 HighFree: Highmem is all memory above ~860MB of physical memory
731 Highmem areas are for use by userspace programs, or
732 for the pagecache. The kernel must use tricks to access
733 this memory, making it slower to access than lowmem.
734 LowTotal:
735 LowFree: Lowmem is memory which can be used for everything that
736 highmem can be used for, but it is also available for the
737 kernel's use for its own data structures. Among many
738 other things, it is where everything from the Slab is
739 allocated. Bad things happen when you're out of lowmem.
740 SwapTotal: total amount of swap space available
741 SwapFree: Memory which has been evicted from RAM, and is temporarily
742 on the disk
743 Dirty: Memory which is waiting to get written back to the disk
744 Writeback: Memory which is actively being written back to the disk
745 AnonPages: Non-file backed pages mapped into userspace page tables
746 Mapped: files which have been mmaped, such as libraries
747 Slab: in-kernel data structures cache
748SReclaimable: Part of Slab, that might be reclaimed, such as caches
749 SUnreclaim: Part of Slab, that cannot be reclaimed on memory pressure
750 PageTables: amount of memory dedicated to the lowest level of page
751 tables.
752NFS_Unstable: NFS pages sent to the server, but not yet committed to stable
753 storage
754 Bounce: Memory used for block device "bounce buffers"
755WritebackTmp: Memory used by FUSE for temporary writeback buffers
756 CommitLimit: Based on the overcommit ratio ('vm.overcommit_ratio'),
757 this is the total amount of memory currently available to
758 be allocated on the system. This limit is only adhered to
759 if strict overcommit accounting is enabled (mode 2 in
760 'vm.overcommit_memory').
761 The CommitLimit is calculated with the following formula:
762 CommitLimit = ('vm.overcommit_ratio' * Physical RAM) + Swap
763 For example, on a system with 1G of physical RAM and 7G
764 of swap with a `vm.overcommit_ratio` of 30 it would
765 yield a CommitLimit of 7.3G.
766 For more details, see the memory overcommit documentation
767 in vm/overcommit-accounting.
768Committed_AS: The amount of memory presently allocated on the system.
769 The committed memory is a sum of all of the memory which
770 has been allocated by processes, even if it has not been
771 "used" by them as of yet. A process which malloc()'s 1G
772 of memory, but only touches 300M of it will only show up
773 as using 300M of memory even if it has the address space
774 allocated for the entire 1G. This 1G is memory which has
775 been "committed" to by the VM and can be used at any time
776 by the allocating application. With strict overcommit
777 enabled on the system (mode 2 in 'vm.overcommit_memory'),
778 allocations which would exceed the CommitLimit (detailed
779 above) will not be permitted. This is useful if one needs
780 to guarantee that processes will not fail due to lack of
781 memory once that memory has been successfully allocated.
782VmallocTotal: total size of vmalloc memory area
783 VmallocUsed: amount of vmalloc area which is used
784VmallocChunk: largest contiguous block of vmalloc area which is free
785
786..............................................................................
787
788vmallocinfo:
789
790Provides information about vmalloced/vmaped areas. One line per area,
791containing the virtual address range of the area, size in bytes,
792caller information of the creator, and optional information depending
793on the kind of area :
794
795 pages=nr number of pages
796 phys=addr if a physical address was specified
797 ioremap I/O mapping (ioremap() and friends)
798 vmalloc vmalloc() area
799 vmap vmap()ed pages
800 user VM_USERMAP area
801 vpages buffer for pages pointers was vmalloced (huge area)
802 N<node>=nr (Only on NUMA kernels)
803 Number of pages allocated on memory node <node>
804
805> cat /proc/vmallocinfo
8060xffffc20000000000-0xffffc20000201000 2101248 alloc_large_system_hash+0x204 ...
807 /0x2c0 pages=512 vmalloc N0=128 N1=128 N2=128 N3=128
8080xffffc20000201000-0xffffc20000302000 1052672 alloc_large_system_hash+0x204 ...
809 /0x2c0 pages=256 vmalloc N0=64 N1=64 N2=64 N3=64
8100xffffc20000302000-0xffffc20000304000 8192 acpi_tb_verify_table+0x21/0x4f...
811 phys=7fee8000 ioremap
8120xffffc20000304000-0xffffc20000307000 12288 acpi_tb_verify_table+0x21/0x4f...
813 phys=7fee7000 ioremap
8140xffffc2000031d000-0xffffc2000031f000 8192 init_vdso_vars+0x112/0x210
8150xffffc2000031f000-0xffffc2000032b000 49152 cramfs_uncompress_init+0x2e ...
816 /0x80 pages=11 vmalloc N0=3 N1=3 N2=2 N3=3
8170xffffc2000033a000-0xffffc2000033d000 12288 sys_swapon+0x640/0xac0 ...
818 pages=2 vmalloc N1=2
8190xffffc20000347000-0xffffc2000034c000 20480 xt_alloc_table_info+0xfe ...
820 /0x130 [x_tables] pages=4 vmalloc N0=4
8210xffffffffa0000000-0xffffffffa000f000 61440 sys_init_module+0xc27/0x1d00 ...
822 pages=14 vmalloc N2=14
8230xffffffffa000f000-0xffffffffa0014000 20480 sys_init_module+0xc27/0x1d00 ...
824 pages=4 vmalloc N1=4
8250xffffffffa0014000-0xffffffffa0017000 12288 sys_init_module+0xc27/0x1d00 ...
826 pages=2 vmalloc N1=2
8270xffffffffa0017000-0xffffffffa0022000 45056 sys_init_module+0xc27/0x1d00 ...
828 pages=10 vmalloc N0=10
829
830..............................................................................
831
832softirqs:
833
834Provides counts of softirq handlers serviced since boot time, for each cpu.
835
836> cat /proc/softirqs
837 CPU0 CPU1 CPU2 CPU3
838 HI: 0 0 0 0
839 TIMER: 27166 27120 27097 27034
840 NET_TX: 0 0 0 17
841 NET_RX: 42 0 0 39
842 BLOCK: 0 0 107 1121
843 TASKLET: 0 0 0 290
844 SCHED: 27035 26983 26971 26746
845 HRTIMER: 0 0 0 0
846 RCU: 1678 1769 2178 2250
847
848
8491.3 IDE devices in /proc/ide
850----------------------------
851
852The subdirectory /proc/ide contains information about all IDE devices of which
853the kernel is aware. There is one subdirectory for each IDE controller, the
854file drivers and a link for each IDE device, pointing to the device directory
855in the controller specific subtree.
856
857The file drivers contains general information about the drivers used for the
858IDE devices:
859
860 > cat /proc/ide/drivers
861 ide-cdrom version 4.53
862 ide-disk version 1.08
863
864More detailed information can be found in the controller specific
865subdirectories. These are named ide0, ide1 and so on. Each of these
866directories contains the files shown in table 1-6.
867
868
869Table 1-6: IDE controller info in /proc/ide/ide?
870..............................................................................
871 File Content
872 channel IDE channel (0 or 1)
873 config Configuration (only for PCI/IDE bridge)
874 mate Mate name
875 model Type/Chipset of IDE controller
876..............................................................................
877
878Each device connected to a controller has a separate subdirectory in the
879controllers directory. The files listed in table 1-7 are contained in these
880directories.
881
882
883Table 1-7: IDE device information
884..............................................................................
885 File Content
886 cache The cache
887 capacity Capacity of the medium (in 512Byte blocks)
888 driver driver and version
889 geometry physical and logical geometry
890 identify device identify block
891 media media type
892 model device identifier
893 settings device setup
894 smart_thresholds IDE disk management thresholds
895 smart_values IDE disk management values
896..............................................................................
897
898The most interesting file is settings. This file contains a nice overview of
899the drive parameters:
900
901 # cat /proc/ide/ide0/hda/settings
902 name value min max mode
903 ---- ----- --- --- ----
904 bios_cyl 526 0 65535 rw
905 bios_head 255 0 255 rw
906 bios_sect 63 0 63 rw
907 breada_readahead 4 0 127 rw
908 bswap 0 0 1 r
909 file_readahead 72 0 2097151 rw
910 io_32bit 0 0 3 rw
911 keepsettings 0 0 1 rw
912 max_kb_per_request 122 1 127 rw
913 multcount 0 0 8 rw
914 nice1 1 0 1 rw
915 nowerr 0 0 1 rw
916 pio_mode write-only 0 255 w
917 slow 0 0 1 rw
918 unmaskirq 0 0 1 rw
919 using_dma 0 0 1 rw
920
921
9221.4 Networking info in /proc/net
923--------------------------------
924
925The subdirectory /proc/net follows the usual pattern. Table 1-8 shows the
926additional values you get for IP version 6 if you configure the kernel to
927support this. Table 1-9 lists the files and their meaning.
928
929
930Table 1-8: IPv6 info in /proc/net
931..............................................................................
932 File Content
933 udp6 UDP sockets (IPv6)
934 tcp6 TCP sockets (IPv6)
935 raw6 Raw device statistics (IPv6)
936 igmp6 IP multicast addresses, which this host joined (IPv6)
937 if_inet6 List of IPv6 interface addresses
938 ipv6_route Kernel routing table for IPv6
939 rt6_stats Global IPv6 routing tables statistics
940 sockstat6 Socket statistics (IPv6)
941 snmp6 Snmp data (IPv6)
942..............................................................................
943
944
945Table 1-9: Network info in /proc/net
946..............................................................................
947 File Content
948 arp Kernel ARP table
949 dev network devices with statistics
950 dev_mcast the Layer2 multicast groups a device is listening too
951 (interface index, label, number of references, number of bound
952 addresses).
953 dev_stat network device status
954 ip_fwchains Firewall chain linkage
955 ip_fwnames Firewall chain names
956 ip_masq Directory containing the masquerading tables
957 ip_masquerade Major masquerading table
958 netstat Network statistics
959 raw raw device statistics
960 route Kernel routing table
961 rpc Directory containing rpc info
962 rt_cache Routing cache
963 snmp SNMP data
964 sockstat Socket statistics
965 tcp TCP sockets
966 tr_rif Token ring RIF routing table
967 udp UDP sockets
968 unix UNIX domain sockets
969 wireless Wireless interface data (Wavelan etc)
970 igmp IP multicast addresses, which this host joined
971 psched Global packet scheduler parameters.
972 netlink List of PF_NETLINK sockets
973 ip_mr_vifs List of multicast virtual interfaces
974 ip_mr_cache List of multicast routing cache
975..............................................................................
976
977You can use this information to see which network devices are available in
978your system and how much traffic was routed over those devices:
979
980 > cat /proc/net/dev
981 Inter-|Receive |[...
982 face |bytes packets errs drop fifo frame compressed multicast|[...
983 lo: 908188 5596 0 0 0 0 0 0 [...
984 ppp0:15475140 20721 410 0 0 410 0 0 [...
985 eth0: 614530 7085 0 0 0 0 0 1 [...
986
987 ...] Transmit
988 ...] bytes packets errs drop fifo colls carrier compressed
989 ...] 908188 5596 0 0 0 0 0 0
990 ...] 1375103 17405 0 0 0 0 0 0
991 ...] 1703981 5535 0 0 0 3 0 0
992
993In addition, each Channel Bond interface has its own directory. For
994example, the bond0 device will have a directory called /proc/net/bond0/.
995It will contain information that is specific to that bond, such as the
996current slaves of the bond, the link status of the slaves, and how
997many times the slaves link has failed.
998
9991.5 SCSI info
1000-------------
1001
1002If you have a SCSI host adapter in your system, you'll find a subdirectory
1003named after the driver for this adapter in /proc/scsi. You'll also see a list
1004of all recognized SCSI devices in /proc/scsi:
1005
1006 >cat /proc/scsi/scsi
1007 Attached devices:
1008 Host: scsi0 Channel: 00 Id: 00 Lun: 00
1009 Vendor: IBM Model: DGHS09U Rev: 03E0
1010 Type: Direct-Access ANSI SCSI revision: 03
1011 Host: scsi0 Channel: 00 Id: 06 Lun: 00
1012 Vendor: PIONEER Model: CD-ROM DR-U06S Rev: 1.04
1013 Type: CD-ROM ANSI SCSI revision: 02
1014
1015
1016The directory named after the driver has one file for each adapter found in
1017the system. These files contain information about the controller, including
1018the used IRQ and the IO address range. The amount of information shown is
1019dependent on the adapter you use. The example shows the output for an Adaptec
1020AHA-2940 SCSI adapter:
1021
1022 > cat /proc/scsi/aic7xxx/0
1023
1024 Adaptec AIC7xxx driver version: 5.1.19/3.2.4
1025 Compile Options:
1026 TCQ Enabled By Default : Disabled
1027 AIC7XXX_PROC_STATS : Disabled
1028 AIC7XXX_RESET_DELAY : 5
1029 Adapter Configuration:
1030 SCSI Adapter: Adaptec AHA-294X Ultra SCSI host adapter
1031 Ultra Wide Controller
1032 PCI MMAPed I/O Base: 0xeb001000
1033 Adapter SEEPROM Config: SEEPROM found and used.
1034 Adaptec SCSI BIOS: Enabled
1035 IRQ: 10
1036 SCBs: Active 0, Max Active 2,
1037 Allocated 15, HW 16, Page 255
1038 Interrupts: 160328
1039 BIOS Control Word: 0x18b6
1040 Adapter Control Word: 0x005b
1041 Extended Translation: Enabled
1042 Disconnect Enable Flags: 0xffff
1043 Ultra Enable Flags: 0x0001
1044 Tag Queue Enable Flags: 0x0000
1045 Ordered Queue Tag Flags: 0x0000
1046 Default Tag Queue Depth: 8
1047 Tagged Queue By Device array for aic7xxx host instance 0:
1048 {255,255,255,255,255,255,255,255,255,255,255,255,255,255,255,255}
1049 Actual queue depth per device for aic7xxx host instance 0:
1050 {1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1}
1051 Statistics:
1052 (scsi0:0:0:0)
1053 Device using Wide/Sync transfers at 40.0 MByte/sec, offset 8
1054 Transinfo settings: current(12/8/1/0), goal(12/8/1/0), user(12/15/1/0)
1055 Total transfers 160151 (74577 reads and 85574 writes)
1056 (scsi0:0:6:0)
1057 Device using Narrow/Sync transfers at 5.0 MByte/sec, offset 15
1058 Transinfo settings: current(50/15/0/0), goal(50/15/0/0), user(50/15/0/0)
1059 Total transfers 0 (0 reads and 0 writes)
1060
1061
10621.6 Parallel port info in /proc/parport
1063---------------------------------------
1064
1065The directory /proc/parport contains information about the parallel ports of
1066your system. It has one subdirectory for each port, named after the port
1067number (0,1,2,...).
1068
1069These directories contain the four files shown in Table 1-10.
1070
1071
1072Table 1-10: Files in /proc/parport
1073..............................................................................
1074 File Content
1075 autoprobe Any IEEE-1284 device ID information that has been acquired.
1076 devices list of the device drivers using that port. A + will appear by the
1077 name of the device currently using the port (it might not appear
1078 against any).
1079 hardware Parallel port's base address, IRQ line and DMA channel.
1080 irq IRQ that parport is using for that port. This is in a separate
1081 file to allow you to alter it by writing a new value in (IRQ
1082 number or none).
1083..............................................................................
1084
10851.7 TTY info in /proc/tty
1086-------------------------
1087
1088Information about the available and actually used tty's can be found in the
1089directory /proc/tty.You'll find entries for drivers and line disciplines in
1090this directory, as shown in Table 1-11.
1091
1092
1093Table 1-11: Files in /proc/tty
1094..............................................................................
1095 File Content
1096 drivers list of drivers and their usage
1097 ldiscs registered line disciplines
1098 driver/serial usage statistic and status of single tty lines
1099..............................................................................
1100
1101To see which tty's are currently in use, you can simply look into the file
1102/proc/tty/drivers:
1103
1104 > cat /proc/tty/drivers
1105 pty_slave /dev/pts 136 0-255 pty:slave
1106 pty_master /dev/ptm 128 0-255 pty:master
1107 pty_slave /dev/ttyp 3 0-255 pty:slave
1108 pty_master /dev/pty 2 0-255 pty:master
1109 serial /dev/cua 5 64-67 serial:callout
1110 serial /dev/ttyS 4 64-67 serial
1111 /dev/tty0 /dev/tty0 4 0 system:vtmaster
1112 /dev/ptmx /dev/ptmx 5 2 system
1113 /dev/console /dev/console 5 1 system:console
1114 /dev/tty /dev/tty 5 0 system:/dev/tty
1115 unknown /dev/tty 4 1-63 console
1116
1117
11181.8 Miscellaneous kernel statistics in /proc/stat
1119-------------------------------------------------
1120
1121Various pieces of information about kernel activity are available in the
1122/proc/stat file. All of the numbers reported in this file are aggregates
1123since the system first booted. For a quick look, simply cat the file:
1124
1125 > cat /proc/stat
1126 cpu 2255 34 2290 22625563 6290 127 456 0 0
1127 cpu0 1132 34 1441 11311718 3675 127 438 0 0
1128 cpu1 1123 0 849 11313845 2614 0 18 0 0
1129 intr 114930548 113199788 3 0 5 263 0 4 [... lots more numbers ...]
1130 ctxt 1990473
1131 btime 1062191376
1132 processes 2915
1133 procs_running 1
1134 procs_blocked 0
1135 softirq 183433 0 21755 12 39 1137 231 21459 2263
1136
1137The very first "cpu" line aggregates the numbers in all of the other "cpuN"
1138lines. These numbers identify the amount of time the CPU has spent performing
1139different kinds of work. Time units are in USER_HZ (typically hundredths of a
1140second). The meanings of the columns are as follows, from left to right:
1141
1142- user: normal processes executing in user mode
1143- nice: niced processes executing in user mode
1144- system: processes executing in kernel mode
1145- idle: twiddling thumbs
1146- iowait: waiting for I/O to complete
1147- irq: servicing interrupts
1148- softirq: servicing softirqs
1149- steal: involuntary wait
1150- guest: running a normal guest
1151- guest_nice: running a niced guest
1152
1153The "intr" line gives counts of interrupts serviced since boot time, for each
1154of the possible system interrupts. The first column is the total of all
1155interrupts serviced; each subsequent column is the total for that particular
1156interrupt.
1157
1158The "ctxt" line gives the total number of context switches across all CPUs.
1159
1160The "btime" line gives the time at which the system booted, in seconds since
1161the Unix epoch.
1162
1163The "processes" line gives the number of processes and threads created, which
1164includes (but is not limited to) those created by calls to the fork() and
1165clone() system calls.
1166
1167The "procs_running" line gives the total number of threads that are
1168running or ready to run (i.e., the total number of runnable threads).
1169
1170The "procs_blocked" line gives the number of processes currently blocked,
1171waiting for I/O to complete.
1172
1173The "softirq" line gives counts of softirqs serviced since boot time, for each
1174of the possible system softirqs. The first column is the total of all
1175softirqs serviced; each subsequent column is the total for that particular
1176softirq.
1177
1178
11791.9 Ext4 file system parameters
1180------------------------------
1181
1182Information about mounted ext4 file systems can be found in
1183/proc/fs/ext4. Each mounted filesystem will have a directory in
1184/proc/fs/ext4 based on its device name (i.e., /proc/fs/ext4/hdc or
1185/proc/fs/ext4/dm-0). The files in each per-device directory are shown
1186in Table 1-12, below.
1187
1188Table 1-12: Files in /proc/fs/ext4/<devname>
1189..............................................................................
1190 File Content
1191 mb_groups details of multiblock allocator buddy cache of free blocks
1192..............................................................................
1193
11942.0 /proc/consoles
1195------------------
1196Shows registered system console lines.
1197
1198To see which character device lines are currently used for the system console
1199/dev/console, you may simply look into the file /proc/consoles:
1200
1201 > cat /proc/consoles
1202 tty0 -WU (ECp) 4:7
1203 ttyS0 -W- (Ep) 4:64
1204
1205The columns are:
1206
1207 device name of the device
1208 operations R = can do read operations
1209 W = can do write operations
1210 U = can do unblank
1211 flags E = it is enabled
1212 C = it is preferred console
1213 B = it is primary boot console
1214 p = it is used for printk buffer
1215 b = it is not a TTY but a Braille device
1216 a = it is safe to use when cpu is offline
1217 major:minor major and minor number of the device separated by a colon
1218
1219------------------------------------------------------------------------------
1220Summary
1221------------------------------------------------------------------------------
1222The /proc file system serves information about the running system. It not only
1223allows access to process data but also allows you to request the kernel status
1224by reading files in the hierarchy.
1225
1226The directory structure of /proc reflects the types of information and makes
1227it easy, if not obvious, where to look for specific data.
1228------------------------------------------------------------------------------
1229
1230------------------------------------------------------------------------------
1231CHAPTER 2: MODIFYING SYSTEM PARAMETERS
1232------------------------------------------------------------------------------
1233
1234------------------------------------------------------------------------------
1235In This Chapter
1236------------------------------------------------------------------------------
1237* Modifying kernel parameters by writing into files found in /proc/sys
1238* Exploring the files which modify certain parameters
1239* Review of the /proc/sys file tree
1240------------------------------------------------------------------------------
1241
1242
1243A very interesting part of /proc is the directory /proc/sys. This is not only
1244a source of information, it also allows you to change parameters within the
1245kernel. Be very careful when attempting this. You can optimize your system,
1246but you can also cause it to crash. Never alter kernel parameters on a
1247production system. Set up a development machine and test to make sure that
1248everything works the way you want it to. You may have no alternative but to
1249reboot the machine once an error has been made.
1250
1251To change a value, simply echo the new value into the file. An example is
1252given below in the section on the file system data. You need to be root to do
1253this. You can create your own boot script to perform this every time your
1254system boots.
1255
1256The files in /proc/sys can be used to fine tune and monitor miscellaneous and
1257general things in the operation of the Linux kernel. Since some of the files
1258can inadvertently disrupt your system, it is advisable to read both
1259documentation and source before actually making adjustments. In any case, be
1260very careful when writing to any of these files. The entries in /proc may
1261change slightly between the 2.1.* and the 2.2 kernel, so if there is any doubt
1262review the kernel documentation in the directory /usr/src/linux/Documentation.
1263This chapter is heavily based on the documentation included in the pre 2.2
1264kernels, and became part of it in version 2.2.1 of the Linux kernel.
1265
1266Please see: Documentation/sysctls/ directory for descriptions of these
1267entries.
1268
1269------------------------------------------------------------------------------
1270Summary
1271------------------------------------------------------------------------------
1272Certain aspects of kernel behavior can be modified at runtime, without the
1273need to recompile the kernel, or even to reboot the system. The files in the
1274/proc/sys tree can not only be read, but also modified. You can use the echo
1275command to write value into these files, thereby changing the default settings
1276of the kernel.
1277------------------------------------------------------------------------------
1278
1279------------------------------------------------------------------------------
1280CHAPTER 3: PER-PROCESS PARAMETERS
1281------------------------------------------------------------------------------
1282
12833.1 /proc/<pid>/oom_adj & /proc/<pid>/oom_score_adj- Adjust the oom-killer score
1284--------------------------------------------------------------------------------
1285
1286These file can be used to adjust the badness heuristic used to select which
1287process gets killed in out of memory conditions.
1288
1289The badness heuristic assigns a value to each candidate task ranging from 0
1290(never kill) to 1000 (always kill) to determine which process is targeted. The
1291units are roughly a proportion along that range of allowed memory the process
1292may allocate from based on an estimation of its current memory and swap use.
1293For example, if a task is using all allowed memory, its badness score will be
12941000. If it is using half of its allowed memory, its score will be 500.
1295
1296There is an additional factor included in the badness score: root
1297processes are given 3% extra memory over other tasks.
1298
1299The amount of "allowed" memory depends on the context in which the oom killer
1300was called. If it is due to the memory assigned to the allocating task's cpuset
1301being exhausted, the allowed memory represents the set of mems assigned to that
1302cpuset. If it is due to a mempolicy's node(s) being exhausted, the allowed
1303memory represents the set of mempolicy nodes. If it is due to a memory
1304limit (or swap limit) being reached, the allowed memory is that configured
1305limit. Finally, if it is due to the entire system being out of memory, the
1306allowed memory represents all allocatable resources.
1307
1308The value of /proc/<pid>/oom_score_adj is added to the badness score before it
1309is used to determine which task to kill. Acceptable values range from -1000
1310(OOM_SCORE_ADJ_MIN) to +1000 (OOM_SCORE_ADJ_MAX). This allows userspace to
1311polarize the preference for oom killing either by always preferring a certain
1312task or completely disabling it. The lowest possible value, -1000, is
1313equivalent to disabling oom killing entirely for that task since it will always
1314report a badness score of 0.
1315
1316Consequently, it is very simple for userspace to define the amount of memory to
1317consider for each task. Setting a /proc/<pid>/oom_score_adj value of +500, for
1318example, is roughly equivalent to allowing the remainder of tasks sharing the
1319same system, cpuset, mempolicy, or memory controller resources to use at least
132050% more memory. A value of -500, on the other hand, would be roughly
1321equivalent to discounting 50% of the task's allowed memory from being considered
1322as scoring against the task.
1323
1324For backwards compatibility with previous kernels, /proc/<pid>/oom_adj may also
1325be used to tune the badness score. Its acceptable values range from -16
1326(OOM_ADJUST_MIN) to +15 (OOM_ADJUST_MAX) and a special value of -17
1327(OOM_DISABLE) to disable oom killing entirely for that task. Its value is
1328scaled linearly with /proc/<pid>/oom_score_adj.
1329
1330Writing to /proc/<pid>/oom_score_adj or /proc/<pid>/oom_adj will change the
1331other with its scaled value.
1332
1333The value of /proc/<pid>/oom_score_adj may be reduced no lower than the last
1334value set by a CAP_SYS_RESOURCE process. To reduce the value any lower
1335requires CAP_SYS_RESOURCE.
1336
1337NOTICE: /proc/<pid>/oom_adj is deprecated and will be removed, please see
1338Documentation/feature-removal-schedule.txt.
1339
1340Caveat: when a parent task is selected, the oom killer will sacrifice any first
1341generation children with separate address spaces instead, if possible. This
1342avoids servers and important system daemons from being killed and loses the
1343minimal amount of work.
1344
1345
13463.2 /proc/<pid>/oom_score - Display current oom-killer score
1347-------------------------------------------------------------
1348
1349This file can be used to check the current score used by the oom-killer is for
1350any given <pid>. Use it together with /proc/<pid>/oom_adj to tune which
1351process should be killed in an out-of-memory situation.
1352
1353
13543.3 /proc/<pid>/io - Display the IO accounting fields
1355-------------------------------------------------------
1356
1357This file contains IO statistics for each running process
1358
1359Example
1360-------
1361
1362test:/tmp # dd if=/dev/zero of=/tmp/test.dat &
1363[1] 3828
1364
1365test:/tmp # cat /proc/3828/io
1366rchar: 323934931
1367wchar: 323929600
1368syscr: 632687
1369syscw: 632675
1370read_bytes: 0
1371write_bytes: 323932160
1372cancelled_write_bytes: 0
1373
1374
1375Description
1376-----------
1377
1378rchar
1379-----
1380
1381I/O counter: chars read
1382The number of bytes which this task has caused to be read from storage. This
1383is simply the sum of bytes which this process passed to read() and pread().
1384It includes things like tty IO and it is unaffected by whether or not actual
1385physical disk IO was required (the read might have been satisfied from
1386pagecache)
1387
1388
1389wchar
1390-----
1391
1392I/O counter: chars written
1393The number of bytes which this task has caused, or shall cause to be written
1394to disk. Similar caveats apply here as with rchar.
1395
1396
1397syscr
1398-----
1399
1400I/O counter: read syscalls
1401Attempt to count the number of read I/O operations, i.e. syscalls like read()
1402and pread().
1403
1404
1405syscw
1406-----
1407
1408I/O counter: write syscalls
1409Attempt to count the number of write I/O operations, i.e. syscalls like
1410write() and pwrite().
1411
1412
1413read_bytes
1414----------
1415
1416I/O counter: bytes read
1417Attempt to count the number of bytes which this process really did cause to
1418be fetched from the storage layer. Done at the submit_bio() level, so it is
1419accurate for block-backed filesystems. <please add status regarding NFS and
1420CIFS at a later time>
1421
1422
1423write_bytes
1424-----------
1425
1426I/O counter: bytes written
1427Attempt to count the number of bytes which this process caused to be sent to
1428the storage layer. This is done at page-dirtying time.
1429
1430
1431cancelled_write_bytes
1432---------------------
1433
1434The big inaccuracy here is truncate. If a process writes 1MB to a file and
1435then deletes the file, it will in fact perform no writeout. But it will have
1436been accounted as having caused 1MB of write.
1437In other words: The number of bytes which this process caused to not happen,
1438by truncating pagecache. A task can cause "negative" IO too. If this task
1439truncates some dirty pagecache, some IO which another task has been accounted
1440for (in its write_bytes) will not be happening. We _could_ just subtract that
1441from the truncating task's write_bytes, but there is information loss in doing
1442that.
1443
1444
1445Note
1446----
1447
1448At its current implementation state, this is a bit racy on 32-bit machines: if
1449process A reads process B's /proc/pid/io while process B is updating one of
1450those 64-bit counters, process A could see an intermediate result.
1451
1452
1453More information about this can be found within the taskstats documentation in
1454Documentation/accounting.
1455
14563.4 /proc/<pid>/coredump_filter - Core dump filtering settings
1457---------------------------------------------------------------
1458When a process is dumped, all anonymous memory is written to a core file as
1459long as the size of the core file isn't limited. But sometimes we don't want
1460to dump some memory segments, for example, huge shared memory. Conversely,
1461sometimes we want to save file-backed memory segments into a core file, not
1462only the individual files.
1463
1464/proc/<pid>/coredump_filter allows you to customize which memory segments
1465will be dumped when the <pid> process is dumped. coredump_filter is a bitmask
1466of memory types. If a bit of the bitmask is set, memory segments of the
1467corresponding memory type are dumped, otherwise they are not dumped.
1468
1469The following 7 memory types are supported:
1470 - (bit 0) anonymous private memory
1471 - (bit 1) anonymous shared memory
1472 - (bit 2) file-backed private memory
1473 - (bit 3) file-backed shared memory
1474 - (bit 4) ELF header pages in file-backed private memory areas (it is
1475 effective only if the bit 2 is cleared)
1476 - (bit 5) hugetlb private memory
1477 - (bit 6) hugetlb shared memory
1478
1479 Note that MMIO pages such as frame buffer are never dumped and vDSO pages
1480 are always dumped regardless of the bitmask status.
1481
1482 Note bit 0-4 doesn't effect any hugetlb memory. hugetlb memory are only
1483 effected by bit 5-6.
1484
1485Default value of coredump_filter is 0x23; this means all anonymous memory
1486segments and hugetlb private memory are dumped.
1487
1488If you don't want to dump all shared memory segments attached to pid 1234,
1489write 0x21 to the process's proc file.
1490
1491 $ echo 0x21 > /proc/1234/coredump_filter
1492
1493When a new process is created, the process inherits the bitmask status from its
1494parent. It is useful to set up coredump_filter before the program runs.
1495For example:
1496
1497 $ echo 0x7 > /proc/self/coredump_filter
1498 $ ./some_program
1499
15003.5 /proc/<pid>/mountinfo - Information about mounts
1501--------------------------------------------------------
1502
1503This file contains lines of the form:
1504
150536 35 98:0 /mnt1 /mnt2 rw,noatime master:1 - ext3 /dev/root rw,errors=continue
1506(1)(2)(3) (4) (5) (6) (7) (8) (9) (10) (11)
1507
1508(1) mount ID: unique identifier of the mount (may be reused after umount)
1509(2) parent ID: ID of parent (or of self for the top of the mount tree)
1510(3) major:minor: value of st_dev for files on filesystem
1511(4) root: root of the mount within the filesystem
1512(5) mount point: mount point relative to the process's root
1513(6) mount options: per mount options
1514(7) optional fields: zero or more fields of the form "tag[:value]"
1515(8) separator: marks the end of the optional fields
1516(9) filesystem type: name of filesystem of the form "type[.subtype]"
1517(10) mount source: filesystem specific information or "none"
1518(11) super options: per super block options
1519
1520Parsers should ignore all unrecognised optional fields. Currently the
1521possible optional fields are:
1522
1523shared:X mount is shared in peer group X
1524master:X mount is slave to peer group X
1525propagate_from:X mount is slave and receives propagation from peer group X (*)
1526unbindable mount is unbindable
1527
1528(*) X is the closest dominant peer group under the process's root. If
1529X is the immediate master of the mount, or if there's no dominant peer
1530group under the same root, then only the "master:X" field is present
1531and not the "propagate_from:X" field.
1532
1533For more information on mount propagation see:
1534
1535 Documentation/filesystems/sharedsubtree.txt
1536
1537
15383.6 /proc/<pid>/comm & /proc/<pid>/task/<tid>/comm
1539--------------------------------------------------------
1540These files provide a method to access a tasks comm value. It also allows for
1541a task to set its own or one of its thread siblings comm value. The comm value
1542is limited in size compared to the cmdline value, so writing anything longer
1543then the kernel's TASK_COMM_LEN (currently 16 chars) will result in a truncated
1544comm value.