proc.txt

《嵌入式系统设计与实例开发实验教材二源码》Linux内核移植与编译实验

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                       T H E  /proc   F I L E S Y S T E M
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/proc/sys         Terrehon Bowden <[e-mail]>        October 7 1999
                  Bodo Bauer <[e-mail]>

2.4.x update	  Jorge Nerin <[e-mail]>      November 14 2000
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Version 1.3                                              Kernel version 2.2.12
					      Kernel version 2.4.0-test11-pre4
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Table of Contents
-----------------

  0     Preface
  0.1	Introduction/Credits
  0.2	Legal Stuff

  1	Collecting System Information
  1.1	Process-Specific Subdirectories
  1.2	Kernel data
  1.3	IDE devices in /proc/ide
  1.4	Networking info in /proc/net
  1.5	SCSI info
  1.6	Parallel port info in /proc/parport
  1.7	TTY info in /proc/tty

  2	Modifying System Parameters
  2.1	/proc/sys/fs - File system data
  2.2	/proc/sys/fs/binfmt_misc - Miscellaneous binary formats
  2.3	/proc/sys/kernel - general kernel parameters
  2.4	/proc/sys/vm - The virtual memory subsystem
  2.5	/proc/sys/dev - Device specific parameters
  2.6	/proc/sys/sunrpc - Remote procedure calls
  2.7	/proc/sys/net - Networking stuff
  2.8	/proc/sys/net/ipv4 - IPV4 settings
  2.9	Appletalk
  2.10	IPX

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Preface
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0.1 Introduction/Credits
------------------------

This documentation is  part of a soon (or  so we hope) to be  released book on
the SuSE  Linux distribution. As  there is  no complete documentation  for the
/proc file system and we've used  many freely available sources to write these
chapters, it  seems only fair  to give the work  back to the  Linux community.
This work is  based on the 2.2.*  kernel version and the  upcoming 2.4.*. I'm
afraid it's still far from complete, but we  hope it will be useful. As far as
we know, it is the first 'all-in-one' document about the /proc file system. It
is focused  on the Intel  x86 hardware,  so if you  are looking for  PPC, ARM,
SPARC, APX, etc., features, you probably  won't find what you are looking for.
It also only covers IPv4 networking, not IPv6 nor other protocols - sorry. But
additions and patches  are welcome and will  be added to this  document if you
mail them to Bodo.

We'd like  to  thank Alan Cox, Rik van Riel, and Alexey Kuznetsov and a lot of
other people for help compiling this documentation. We'd also like to extend a
special thank  you to Andi Kleen for documentation, which we relied on heavily
to create  this  document,  as well as the additional information he provided.
Thanks to  everybody  else  who contributed source or docs to the Linux kernel
and helped create a great piece of software... :)

If you  have  any comments, corrections or additions, please don't hesitate to
contact Bodo  Bauer  at  [e-mail].  We'll  be happy to add them to this
document.

The   latest   version    of   this   document   is    available   online   at
http://skaro.nightcrawler.com/~bb/Docs/Proc as HTML version.

If  the above  direction does  not works  for you,  ypu could  try the  kernel
mailing  list  at  [e-mail]  and/or try  to  reach  me  at
[e-mail].

0.2 Legal Stuff
---------------

We don't  guarantee  the  correctness  of this document, and if you come to us
complaining about  how  you  screwed  up  your  system  because  of  incorrect
documentation, we won't feel responsible...

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CHAPTER 1: COLLECTING SYSTEM INFORMATION
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------------------------------------------------------------------------------
In This Chapter
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* Investigating  the  properties  of  the  pseudo  file  system  /proc and its
  ability to provide information on the running Linux system
* Examining /proc's structure
* Uncovering  various  information  about the kernel and the processes running
  on the system
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The proc  file  system acts as an interface to internal data structures in the
kernel. It  can  be  used to obtain information about the system and to change
certain kernel parameters at runtime (sysctl).

First, we'll  take  a  look  at the read-only parts of /proc. In Chapter 2, we
show you how you can use /proc/sys to change settings.

1.1 Process-Specific Subdirectories
-----------------------------------

The directory  /proc  contains  (among other things) one subdirectory for each
process running on the system, which is named after the process ID (PID).

The link  self  points  to  the  process reading the file system. Each process
subdirectory has the entries listed in Table 1-1.


Table 1-1: Process specific entries in /proc 
..............................................................................
 File    Content                                        
 cmdline Command line arguments                         
 cpu	 Current and last cpu in wich it was executed		(2.4)(smp)
 cwd	 Link to the current working directory
 environ Values of environment variables      
 exe	 Link to the executable of this process
 fd      Directory, which contains all file descriptors 
 maps	 Memory maps to executables and library files		(2.4)
 mem     Memory held by this process                    
 root	 Link to the root directory of this process
 stat    Process status                                 
 statm   Process memory status information              
 status  Process status in human readable form          
..............................................................................

For example, to get the status information of a process, all you have to do is
read the file /proc/PID/status:

  >cat /proc/self/status 
  Name:   cat 
  State:  R (running) 
  Pid:    5452 
  PPid:   743 
  TracerPid:      0						(2.4)
  Uid:    501     501     501     501 
  Gid:    100     100     100     100 
  Groups: 100 14 16 
  VmSize:     1112 kB 
  VmLck:         0 kB 
  VmRSS:       348 kB 
  VmData:       24 kB 
  VmStk:        12 kB 
  VmExe:         8 kB 
  VmLib:      1044 kB 
  SigPnd: 0000000000000000 
  SigBlk: 0000000000000000 
  SigIgn: 0000000000000000 
  SigCgt: 0000000000000000 
  CapInh: 00000000fffffeff 
  CapPrm: 0000000000000000 
  CapEff: 0000000000000000 


This shows you nearly the same information you would get if you viewed it with
the ps  command.  In  fact,  ps  uses  the  proc  file  system  to  obtain its
information. The  statm  file  contains  more  detailed  information about the
process memory usage. Its seven fields are explained in Table 1-2.


Table 1-2: Contents of the statm files 
..............................................................................
 File     Content                         
 size     total program size              
 resident size of memory portions         
 shared   number of pages that are shared 
 trs      number of pages that are 'code' 
 drs      number of pages of data/stack   
 lrs      number of pages of library      
 dt       number of dirty pages           
..............................................................................

1.2 Kernel data
---------------

Similar to  the  process entries, the kernel data files give information about
the running kernel. The files used to obtain this information are contained in
/proc and  are  listed  in Table 1-3. Not all of these will be present in your
system. It  depends  on the kernel configuration and the loaded modules, which
files are there, and which are missing.

Table 1-3: Kernel info in /proc 
..............................................................................
 File        Content                                           
 apm         Advanced power management info                    
 bus         Directory containing bus specific information     
 cmdline     Kernel command line                               
 cpuinfo     Info about the CPU                                
 devices     Available devices (block and character)           
 dma         Used DMS channels                                 
 filesystems Supported filesystems                             
 driver	     Various drivers grouped here, currently rtc	(2.4)
 execdomains Execdomains, related to security			(2.4)
 fb	     Frame Buffer devices				(2.4)
 fs	     File system parameters, currently nfs/exports	(2.4)
 ide         Directory containing info about the IDE subsystem 
 interrupts  Interrupt usage                                   
 iomem	     Memory map						(2.4)
 ioports     I/O port usage                                    
 irq	     Masks for irq to cpu affinity			(2.4)(smp?)
 isapnp	     ISA PnP (Plug&Play) Info				(2.4)
 kcore       Kernel core image (can be ELF or A.OUT(deprecated in 2.4))   
 kmsg        Kernel messages                                   
 ksyms       Kernel symbol table                               
 loadavg     Load average of last 1, 5 & 15 minutes                
 locks       Kernel locks                                      
 meminfo     Memory info                                       
 misc        Miscellaneous                                     
 modules     List of loaded modules                            
 mounts      Mounted filesystems                               
 net         Networking info (see text)                        
 partitions  Table of partitions known to the system           
 pci	     Depreciated info of PCI bus (new way -> /proc/bus/pci/, 
             decoupled by lspci					(2.4)
 rtc         Real time clock                                   
 scsi        SCSI info (see text)                              
 slabinfo    Slab pool info                                    
 stat        Overall statistics                                
 swaps       Swap space utilization                            
 sys         See chapter 2                                     
 sysvipc     Info of SysVIPC Resources (msg, sem, shm)		(2.4)
 tty	     Info of tty drivers
 uptime      System uptime                                     
 version     Kernel version                                    
 video	     bttv info of video resources			(2.4)
..............................................................................

You can,  for  example,  check  which interrupts are currently in use and what
they are used for by looking in the file /proc/interrupts:

  > cat /proc/interrupts 
             CPU0        
    0:    8728810          XT-PIC  timer 
    1:        895          XT-PIC  keyboard 
    2:          0          XT-PIC  cascade 
    3:     531695          XT-PIC  aha152x 
    4:    2014133          XT-PIC  serial 
    5:      44401          XT-PIC  pcnet_cs 
    8:          2          XT-PIC  rtc 
   11:          8          XT-PIC  i82365 
   12:     182918          XT-PIC  PS/2 Mouse 
   13:          1          XT-PIC  fpu 
   14:    1232265          XT-PIC  ide0 
   15:          7          XT-PIC  ide1 
  NMI:          0 

In 2.4.* a couple of lines where added to this file LOC & ERR (this time is the
output of a SMP machine):

  > cat /proc/interrupts 

             CPU0       CPU1       
    0:    1243498    1214548    IO-APIC-edge  timer
    1:       8949       8958    IO-APIC-edge  keyboard
    2:          0          0          XT-PIC  cascade
    5:      11286      10161    IO-APIC-edge  soundblaster
    8:          1          0    IO-APIC-edge  rtc
    9:      27422      27407    IO-APIC-edge  3c503
   12:     113645     113873    IO-APIC-edge  PS/2 Mouse
   13:          0          0          XT-PIC  fpu
   14:      22491      24012    IO-APIC-edge  ide0
   15:       2183       2415    IO-APIC-edge  ide1
   17:      30564      30414   IO-APIC-level  eth0
   18:        177        164   IO-APIC-level  bttv
  NMI:    2457961    2457959 
  LOC:    2457882    2457881 
  ERR:       2155

NMI is incremented in this case because every timer interrupt generates a NMI
(Non Maskable Interrupt) which is used by the NMI Watchdog to detect lookups.

LOC is the local interrupt counter of the internal APIC of every CPU.

ERR is incremented in the case of errors in the IO-APIC bus (the bus that
connects the CPUs in a SMP system. This means that an error has been detected,
the IO-APIC automatically retry the transmission, so it should not be a big
problem, but you should read the SMP-FAQ.

In this context it could be interesting to note the new irq directory in 2.4.
It could be used to set IRQ to CPU affinity, this means that you can "hook" an
IRQ to only one CPU, or to exclude a CPU of handling IRQs. The contents of the
irq subdir is one subdir for each IRQ, and one file; prof_cpu_mask

For example 
  > ls /proc/irq/
  0  10  12  14  16  18  2  4  6  8  prof_cpu_mask
  1  11  13  15  17  19  3  5  7  9
  > ls /proc/irq/0/
  smp_affinity

The contents of the prof_cpu_mask file and each smp_affinity file for each IRQ
is the same by default:

  > cat /proc/irq/0/smp_affinity 
  ffffffff

It's a bitmask, in wich you can specify wich CPUs can handle the IRQ, you can
set it by doing:

  > echo 1 > /proc/irq/prof_cpu_mask

This means that only the first CPU will handle the IRQ, but you can also echo 5
wich means that only the first and fourth CPU can handle the IRQ.

The way IRQs are routed is handled by the IO-APIC, and it's Round Robin
between all the CPUs which are allowed to handle it. As usual the kernel has
more info than you and does a better job than you, so the defaults are the
best choice for almost everyone.

There are  three  more  important subdirectories in /proc: net, scsi, and sys.
The general  rule  is  that  the  contents,  or  even  the  existence of these
directories, depend  on your kernel configuration. If SCSI is not enabled, the
directory scsi  may  not  exist. The same is true with the net, which is there
only when networking support is present in the running kernel.

The slabinfo  file  gives  information  about  memory usage at the slab level.