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|
------------------------------------------------------------------------------
T H E /proc F I L E S Y S T E M
------------------------------------------------------------------------------
/proc/sys Terrehon Bowden <terrehon@pacbell.net> October 7 1999
Bodo Bauer <bb@ricochet.net>
2.4.x update Jorge Nerin <comandante@zaralinux.com> November 14 2000
move /proc/sys Shen Feng <shen@cn.fujitsu.com> April 1 2009
------------------------------------------------------------------------------
Version 1.3 Kernel version 2.2.12
Kernel version 2.4.0-test11-pre4
------------------------------------------------------------------------------
fixes/update part 1.1 Stefani Seibold <stefani@seibold.net> June 9 2009
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
1.8 Miscellaneous kernel statistics in /proc/stat
1.9 Ext4 file system parameters
2 Modifying System Parameters
3 Per-Process Parameters
3.1 /proc/<pid>/oom_adj & /proc/<pid>/oom_score_adj - Adjust the oom-killer
score
3.2 /proc/<pid>/oom_score - Display current oom-killer score
3.3 /proc/<pid>/io - Display the IO accounting fields
3.4 /proc/<pid>/coredump_filter - Core dump filtering settings
3.5 /proc/<pid>/mountinfo - Information about mounts
3.6 /proc/<pid>/comm & /proc/<pid>/task/<tid>/comm
3.7 /proc/<pid>/task/<tid>/children - Information about task children
3.8 /proc/<pid>/fdinfo/<fd> - Information about opened file
4 Configuring procfs
4.1 Mount options
------------------------------------------------------------------------------
Preface
------------------------------------------------------------------------------
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, AXP, 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 bb@ricochet.net. We'll be happy to add them to this
document.
The latest version of this document is available online at
http://tldp.org/LDP/Linux-Filesystem-Hierarchy/html/proc.html
If the above direction does not works for you, you could try the kernel
mailing list at linux-kernel@vger.kernel.org and/or try to reach me at
comandante@zaralinux.com.
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...
------------------------------------------------------------------------------
CHAPTER 1: COLLECTING SYSTEM INFORMATION
------------------------------------------------------------------------------
------------------------------------------------------------------------------
In This Chapter
------------------------------------------------------------------------------
* 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
------------------------------------------------------------------------------
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
clear_refs Clears page referenced bits shown in smaps output
cmdline Command line arguments
cpu Current and last cpu in which 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
wchan If CONFIG_KALLSYMS is set, a pre-decoded wchan
pagemap Page table
stack Report full stack trace, enable via CONFIG_STACKTRACE
smaps a extension based on maps, showing the memory consumption of
each mapping and flags associated with it
..............................................................................
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)
Tgid: 5452
Pid: 5452
PPid: 743
TracerPid: 0 (2.4)
Uid: 501 501 501 501
Gid: 100 100 100 100
FDSize: 256
Groups: 100 14 16
VmPeak: 5004 kB
VmSize: 5004 kB
VmLck: 0 kB
VmHWM: 476 kB
VmRSS: 476 kB
VmData: 156 kB
VmStk: 88 kB
VmExe: 68 kB
VmLib: 1412 kB
VmPTE: 20 kb
VmSwap: 0 kB
Threads: 1
SigQ: 0/28578
SigPnd: 0000000000000000
ShdPnd: 0000000000000000
SigBlk: 0000000000000000
SigIgn: 0000000000000000
SigCgt: 0000000000000000
CapInh: 00000000fffffeff
CapPrm: 0000000000000000
CapEff: 0000000000000000
CapBnd: ffffffffffffffff
Seccomp: 0
voluntary_ctxt_switches: 0
nonvoluntary_ctxt_switches: 1
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. But you get a more detailed view of the process by reading the
file /proc/PID/status. It fields are described in table 1-2.
The statm file contains more detailed information about the process
memory usage. Its seven fields are explained in Table 1-3. The stat file
contains details information about the process itself. Its fields are
explained in Table 1-4.
(for SMP CONFIG users)
For making accounting scalable, RSS related information are handled in
asynchronous manner and the vaule may not be very precise. To see a precise
snapshot of a moment, you can see /proc/<pid>/smaps file and scan page table.
It's slow but very precise.
Table 1-2: Contents of the status files (as of 2.6.30-rc7)
..............................................................................
Field Content
Name filename of the executable
State state (R is running, S is sleeping, D is sleeping
in an uninterruptible wait, Z is zombie,
T is traced or stopped)
Tgid thread group ID
Pid process id
PPid process id of the parent process
TracerPid PID of process tracing this process (0 if not)
Uid Real, effective, saved set, and file system UIDs
Gid Real, effective, saved set, and file system GIDs
FDSize number of file descriptor slots currently allocated
Groups supplementary group list
VmPeak peak virtual memory size
VmSize total program size
VmLck locked memory size
VmHWM peak resident set size ("high water mark")
VmRSS size of memory portions
VmData size of data, stack, and text segments
VmStk size of data, stack, and text segments
VmExe size of text segment
VmLib size of shared library code
VmPTE size of page table entries
VmSwap size of swap usage (the number of referred swapents)
Threads number of threads
SigQ number of signals queued/max. number for queue
SigPnd bitmap of pending signals for the thread
ShdPnd bitmap of shared pending signals for the process
SigBlk bitmap of blocked signals
SigIgn bitmap of ignored signals
SigCgt bitmap of catched signals
CapInh bitmap of inheritable capabilities
CapPrm bitmap of permitted capabilities
CapEff bitmap of effective capabilities
CapBnd bitmap of capabilities bounding set
Seccomp seccomp mode, like prctl(PR_GET_SECCOMP, ...)
Cpus_allowed mask of CPUs on which this process may run
Cpus_allowed_list Same as previous, but in "list format"
Mems_allowed mask of memory nodes allowed to this process
Mems_allowed_list Same as previous, but in "list format"
voluntary_ctxt_switches number of voluntary context switches
nonvoluntary_ctxt_switches number of non voluntary context switches
..............................................................................
Table 1-3: Contents of the statm files (as of 2.6.8-rc3)
..............................................................................
Field Content
size total program size (pages) (same as VmSize in status)
resident size of memory portions (pages) (same as VmRSS in status)
shared number of pages that are shared (i.e. backed by a file)
trs number of pages that are 'code' (not including libs; broken,
includes data segment)
lrs number of pages of library (always 0 on 2.6)
drs number of pages of data/stack (including libs; broken,
includes library text)
dt number of dirty pages (always 0 on 2.6)
..............................................................................
Table 1-4: Contents of the stat files (as of 2.6.30-rc7)
..............................................................................
Field Content
pid process id
tcomm filename of the executable
state state (R is running, S is sleeping, D is sleeping in an
uninterruptible wait, Z is zombie, T is traced or stopped)
ppid process id of the parent process
pgrp pgrp of the process
sid session id
tty_nr tty the process uses
tty_pgrp pgrp of the tty
flags task flags
min_flt number of minor faults
cmin_flt number of minor faults with child's
maj_flt number of major faults
cmaj_flt number of major faults with child's
utime user mode jiffies
stime kernel mode jiffies
cutime user mode jiffies with child's
cstime kernel mode jiffies with child's
priority priority level
nice nice level
num_threads number of threads
it_real_value (obsolete, always 0)
start_time time the process started after system boot
vsize virtual memory size
rss resident set memory size
rsslim current limit in bytes on the rss
start_code address above which program text can run
end_code address below which program text can run
start_stack address of the start of the main process stack
esp current value of ESP
eip current value of EIP
pending bitmap of pending signals
blocked bitmap of blocked signals
sigign bitmap of ignored signals
sigcatch bitmap of catched signals
wchan address where process went to sleep
0 (place holder)
0 (place holder)
exit_signal signal to send to parent thread on exit
task_cpu which CPU the task is scheduled on
rt_priority realtime priority
policy scheduling policy (man sched_setscheduler)
blkio_ticks time spent waiting for block IO
gtime guest time of the task in jiffies
cgtime guest time of the task children in jiffies
start_data address above which program data+bss is placed
end_data address below which program data+bss is placed
start_brk address above which program heap can be expanded with brk()
arg_start address above which program command line is placed
arg_end address below which program command line is placed
env_start address above which program environment is placed
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