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Based on kernel version 2.6.33. Page generated on 2010-02-24 15:36 EST.

1	------------------------------------------------------------------------------
2	                       T H E  /proc   F I L E S Y S T E M
3	------------------------------------------------------------------------------
4	/proc/sys         Terrehon Bowden <terrehon[AT]pacbell[DOT]net>        October 7 1999
5	                  Bodo Bauer <bb[AT]ricochet[DOT]net>
6	
7	2.4.x update	  Jorge Nerin <comandante[AT]zaralinux[DOT]com>      November 14 2000
8	move /proc/sys	  Shen Feng <shen[AT]cn.fujitsu[DOT]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[AT]seibold[DOT]net>       June 9 2009
14	
15	Table 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 - 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
42	
43	
44	------------------------------------------------------------------------------
45	Preface
46	------------------------------------------------------------------------------
47	
48	0.1 Introduction/Credits
49	------------------------
50	
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.
63	
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... :)
70	
71	If you  have  any comments, corrections or additions, please don't hesitate to
72	contact Bodo  Bauer  at  bb[AT]ricochet.net[DOT]  We'll  be happy to add them to this
73	document.
74	
75	The   latest   version    of   this   document   is    available   online   at
76	http://skaro.nightcrawler.com/~bb/Docs/Proc as HTML version.
77	
78	If  the above  direction does  not works  for you,  ypu could  try the  kernel
79	mailing  list  at  linux-kernel[AT]vger.kernel[DOT]org  and/or try  to  reach  me  at
80	comandante[AT]zaralinux.com[DOT]
81	
82	0.2 Legal Stuff
83	---------------
84	
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...
88	
89	------------------------------------------------------------------------------
90	CHAPTER 1: COLLECTING SYSTEM INFORMATION
91	------------------------------------------------------------------------------
92	
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	------------------------------------------------------------------------------
102	
103	
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).
107	
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.
110	
111	1.1 Process-Specific Subdirectories
112	-----------------------------------
113	
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).
116	
117	The link  self  points  to  the  process reading the file system. Each process
118	subdirectory has the entries listed in Table 1-1.
119	
120	
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	..............................................................................
142	
143	For example, to get the status information of a process, all you have to do is
144	read the file /proc/PID/status:
145	
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
180	
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.
185	
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.
190	
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	..............................................................................
234	
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	..............................................................................
248	
249	
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	..............................................................................
299	
300	The /proc/PID/map file containing the currently mapped memory regions and
301	their access permissions.
302	
303	The format is:
304	
305	address           perms offset  dev   inode      pathname
306	
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]
327	
328	where "address" is the address space in the process that it occupies, "perms"
329	is a set of permissions:
330	
331	 r = read
332	 w = write
333	 x = execute
334	 s = shared
335	 p = private (copy on write)
336	
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:
342	
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
348	
349	 or if empty, the mapping is anonymous.
350	
351	
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:
355	
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
368	
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 sizeâ (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.
376	
377	This file is only present if the CONFIG_MMU kernel configuration option is
378	enabled.
379	
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
384	
385	To clear the bits for the anonymous pages associated with the process
386	    > echo 2 > /proc/PID/clear_refs
387	
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.
391	
392	
393	1.2 Kernel data
394	---------------
395	
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.
401	
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	..............................................................................
450	
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:
453	
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 
469	
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):
472	
473	  > cat /proc/interrupts 
474	
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
491	
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.
494	
495	LOC is the local interrupt counter of the internal APIC of every CPU.
496	
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.
501	
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:
505	
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.
509	
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.
513	
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.
519	
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.
524	
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.
529	
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.
535	
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
542	
543	smp_affinity is a bitmask, in which you can specify which CPUs can handle the
544	IRQ, you can set it by doing:
545	
546	  > echo 1 > /proc/irq/10/smp_affinity
547	
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.
550	
551	The contents of each smp_affinity file is the same by default:
552	
553	  > cat /proc/irq/0/smp_affinity
554	  ffffffff
555	
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.
559	
560	prof_cpu_mask specifies which CPUs are to be profiled by the system wide
561	profiler. Default value is ffffffff (all cpus).
562	
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.
567	
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.
573	
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).
578	
579	..............................................................................
580	
581	> cat /proc/buddyinfo
582	
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 ...
586	
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.
591	
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... 
596	
597	..............................................................................
598	
599	meminfo:
600	
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.
604	
605	> cat /proc/meminfo
606	
607	
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
637	
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
709	
710	..............................................................................
711	
712	vmallocinfo:
713	
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 :
718	
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>
728	
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
753	
754	..............................................................................
755	
756	softirqs:
757	
758	Provides counts of softirq handlers serviced since boot time, for each cpu.
759	
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
771	
772	
773	1.3 IDE devices in /proc/ide
774	----------------------------
775	
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.
780	
781	The file  drivers  contains general information about the drivers used for the
782	IDE devices:
783	
784	  > cat /proc/ide/drivers
785	  ide-cdrom version 4.53
786	  ide-disk version 1.08
787	
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.
791	
792	
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	..............................................................................
801	
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.
805	
806	
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	..............................................................................
821	
822	The most  interesting  file is settings. This file contains a nice overview of
823	the drive parameters:
824	
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 
844	
845	
846	1.4 Networking info in /proc/net
847	--------------------------------
848	
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.
852	
853	
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	..............................................................................
867	
868	
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	..............................................................................
900	
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:
903	
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 [... 
910	   
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 
916	
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.
922	
923	1.5 SCSI info
924	-------------
925	
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:
929	
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 
938	
939	
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:
945	
946	  > cat /proc/scsi/aic7xxx/0 
947	   
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) 
984	
985	
986	1.6 Parallel port info in /proc/parport
987	---------------------------------------
988	
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,...).
992	
993	These directories contain the four files shown in Table 1-10.
994	
995	
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	..............................................................................
1008	
1009	1.7 TTY info in /proc/tty
1010	-------------------------
1011	
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.
1015	
1016	
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	..............................................................................
1024	
1025	To see  which  tty's  are  currently in use, you can simply look into the file
1026	/proc/tty/drivers:
1027	
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 
1040	
1041	
1042	1.8 Miscellaneous kernel statistics in /proc/stat
1043	-------------------------------------------------
1044	
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:
1048	
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
1060	
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:
1065	
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
1076	
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.
1081	
1082	The "ctxt" line gives the total number of context switches across all CPUs.
1083	
1084	The "btime" line gives  the time at which the  system booted, in seconds since
1085	the Unix epoch.
1086	
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.
1090	
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).
1093	
1094	The   "procs_blocked" line gives  the  number of  processes currently blocked,
1095	waiting for I/O to complete.
1096	
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.
1101	
1102	
1103	1.9 Ext4 file system parameters
1104	------------------------------
1105	
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.
1111	
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	..............................................................................
1117	
1118	
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.
1125	
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	------------------------------------------------------------------------------
1129	
1130	------------------------------------------------------------------------------
1131	CHAPTER 2: MODIFYING SYSTEM PARAMETERS
1132	------------------------------------------------------------------------------
1133	
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	------------------------------------------------------------------------------
1141	
1142	
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.
1150	
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.
1155	
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.
1165	
1166	Please see: Documentation/sysctls/ directory for descriptions of these
1167	entries.
1168	
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	------------------------------------------------------------------------------
1178	
1179	------------------------------------------------------------------------------
1180	CHAPTER 3: PER-PROCESS PARAMETERS
1181	------------------------------------------------------------------------------
1182	
1183	3.1 /proc/<pid>/oom_adj - Adjust the oom-killer score
1184	------------------------------------------------------
1185	
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.
1191	
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.
1198	
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.
1203	
1204	/proc/<pid>/oom_score shows process' current badness score.
1205	
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
1215	
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.
1219	
1220	3.2 /proc/<pid>/oom_score - Display current oom-killer score
1221	-------------------------------------------------------------
1222	
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.
1226	
1227	
1228	3.3  /proc/<pid>/io - Display the IO accounting fields
1229	-------------------------------------------------------
1230	
1231	This file contains IO statistics for each running process
1232	
1233	Example
1234	-------
1235	
1236	test:/tmp # dd if=/dev/zero of=/tmp/test.dat &
1237	[1] 3828
1238	
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
1247	
1248	
1249	Description
1250	-----------
1251	
1252	rchar
1253	-----
1254	
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)
1261	
1262	
1263	wchar
1264	-----
1265	
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.
1269	
1270	
1271	syscr
1272	-----
1273	
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().
1277	
1278	
1279	syscw
1280	-----
1281	
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().
1285	
1286	
1287	read_bytes
1288	----------
1289	
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>
1295	
1296	
1297	write_bytes
1298	-----------
1299	
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.
1303	
1304	
1305	cancelled_write_bytes
1306	---------------------
1307	
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.
1317	
1318	
1319	Note
1320	----
1321	
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.
1325	
1326	
1327	More information about this can be found within the taskstats documentation in
1328	Documentation/accounting.
1329	
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.
1337	
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.
1342	
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
1352	
1353	  Note that MMIO pages such as frame buffer are never dumped and vDSO pages
1354	  are always dumped regardless of the bitmask status.
1355	
1356	  Note bit 0-4 doesn't effect any hugetlb memory. hugetlb memory are only
1357	  effected by bit 5-6.
1358	
1359	Default value of coredump_filter is 0x23; this means all anonymous memory
1360	segments and hugetlb private memory are dumped.
1361	
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.
1364	
1365	  $ echo 0x21 > /proc/1234/coredump_filter
1366	
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:
1370	
1371	  $ echo 0x7 > /proc/self/coredump_filter
1372	  $ ./some_program
1373	
1374	3.5	/proc/<pid>/mountinfo - Information about mounts
1375	--------------------------------------------------------
1376	
1377	This file contains lines of the form:
1378	
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)
1381	
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
1393	
1394	Parsers should ignore all unrecognised optional fields.  Currently the
1395	possible optional fields are:
1396	
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
1401	
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.
1406	
1407	For more information on mount propagation see:
1408	
1409	  Documentation/filesystems/sharedsubtree.txt
1410	
1411	
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.
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