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62 KiB
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1400 lines
62 KiB
Plaintext
------------------------------------------------------------------------------
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T H E /proc F I L E S Y S T E M
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------------------------------------------------------------------------------
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/proc/sys Terrehon Bowden <terrehon@pacbell.net> October 7 1999
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Bodo Bauer <bb@ricochet.net>
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2.4.x update Jorge Nerin <comandante@zaralinux.com> November 14 2000
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move /proc/sys Shen Feng <shen@cn.fujitsu.com> April 1 2009
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------------------------------------------------------------------------------
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Version 1.3 Kernel version 2.2.12
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Kernel version 2.4.0-test11-pre4
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------------------------------------------------------------------------------
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fixes/update part 1.1 Stefani Seibold <stefani@seibold.net> June 9 2009
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Table of Contents
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-----------------
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0 Preface
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0.1 Introduction/Credits
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0.2 Legal Stuff
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1 Collecting System Information
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1.1 Process-Specific Subdirectories
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1.2 Kernel data
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1.3 IDE devices in /proc/ide
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1.4 Networking info in /proc/net
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1.5 SCSI info
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1.6 Parallel port info in /proc/parport
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1.7 TTY info in /proc/tty
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1.8 Miscellaneous kernel statistics in /proc/stat
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1.9 Ext4 file system parameters
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2 Modifying System Parameters
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3 Per-Process Parameters
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3.1 /proc/<pid>/oom_adj - Adjust the oom-killer score
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3.2 /proc/<pid>/oom_score - Display current oom-killer score
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3.3 /proc/<pid>/io - Display the IO accounting fields
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3.4 /proc/<pid>/coredump_filter - Core dump filtering settings
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3.5 /proc/<pid>/mountinfo - Information about mounts
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------------------------------------------------------------------------------
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Preface
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------------------------------------------------------------------------------
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0.1 Introduction/Credits
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------------------------
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This documentation is part of a soon (or so we hope) to be released book on
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the SuSE Linux distribution. As there is no complete documentation for the
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/proc file system and we've used many freely available sources to write these
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chapters, it seems only fair to give the work back to the Linux community.
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This work is based on the 2.2.* kernel version and the upcoming 2.4.*. I'm
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afraid it's still far from complete, but we hope it will be useful. As far as
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we know, it is the first 'all-in-one' document about the /proc file system. It
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is focused on the Intel x86 hardware, so if you are looking for PPC, ARM,
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SPARC, AXP, etc., features, you probably won't find what you are looking for.
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It also only covers IPv4 networking, not IPv6 nor other protocols - sorry. But
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additions and patches are welcome and will be added to this document if you
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mail them to Bodo.
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We'd like to thank Alan Cox, Rik van Riel, and Alexey Kuznetsov and a lot of
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other people for help compiling this documentation. We'd also like to extend a
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special thank you to Andi Kleen for documentation, which we relied on heavily
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to create this document, as well as the additional information he provided.
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Thanks to everybody else who contributed source or docs to the Linux kernel
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and helped create a great piece of software... :)
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If you have any comments, corrections or additions, please don't hesitate to
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contact Bodo Bauer at bb@ricochet.net. We'll be happy to add them to this
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document.
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The latest version of this document is available online at
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http://skaro.nightcrawler.com/~bb/Docs/Proc as HTML version.
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If the above direction does not works for you, ypu could try the kernel
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mailing list at linux-kernel@vger.kernel.org and/or try to reach me at
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comandante@zaralinux.com.
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0.2 Legal Stuff
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---------------
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We don't guarantee the correctness of this document, and if you come to us
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complaining about how you screwed up your system because of incorrect
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documentation, we won't feel responsible...
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------------------------------------------------------------------------------
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CHAPTER 1: COLLECTING SYSTEM INFORMATION
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------------------------------------------------------------------------------
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------------------------------------------------------------------------------
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In This Chapter
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------------------------------------------------------------------------------
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* Investigating the properties of the pseudo file system /proc and its
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ability to provide information on the running Linux system
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* Examining /proc's structure
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* Uncovering various information about the kernel and the processes running
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on the system
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------------------------------------------------------------------------------
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The proc file system acts as an interface to internal data structures in the
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kernel. It can be used to obtain information about the system and to change
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certain kernel parameters at runtime (sysctl).
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First, we'll take a look at the read-only parts of /proc. In Chapter 2, we
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show you how you can use /proc/sys to change settings.
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1.1 Process-Specific Subdirectories
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-----------------------------------
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The directory /proc contains (among other things) one subdirectory for each
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process running on the system, which is named after the process ID (PID).
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The link self points to the process reading the file system. Each process
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subdirectory has the entries listed in Table 1-1.
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Table 1-1: Process specific entries in /proc
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..............................................................................
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File Content
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clear_refs Clears page referenced bits shown in smaps output
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cmdline Command line arguments
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cpu Current and last cpu in which it was executed (2.4)(smp)
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cwd Link to the current working directory
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environ Values of environment variables
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exe Link to the executable of this process
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fd Directory, which contains all file descriptors
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maps Memory maps to executables and library files (2.4)
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mem Memory held by this process
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root Link to the root directory of this process
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stat Process status
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statm Process memory status information
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status Process status in human readable form
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wchan If CONFIG_KALLSYMS is set, a pre-decoded wchan
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stack Report full stack trace, enable via CONFIG_STACKTRACE
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smaps a extension based on maps, showing the memory consumption of
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each mapping
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..............................................................................
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For example, to get the status information of a process, all you have to do is
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read the file /proc/PID/status:
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>cat /proc/self/status
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Name: cat
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State: R (running)
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Tgid: 5452
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Pid: 5452
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PPid: 743
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TracerPid: 0 (2.4)
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Uid: 501 501 501 501
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Gid: 100 100 100 100
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FDSize: 256
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Groups: 100 14 16
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VmPeak: 5004 kB
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VmSize: 5004 kB
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VmLck: 0 kB
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VmHWM: 476 kB
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VmRSS: 476 kB
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VmData: 156 kB
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VmStk: 88 kB
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VmExe: 68 kB
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VmLib: 1412 kB
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VmPTE: 20 kb
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Threads: 1
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SigQ: 0/28578
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SigPnd: 0000000000000000
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ShdPnd: 0000000000000000
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SigBlk: 0000000000000000
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SigIgn: 0000000000000000
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SigCgt: 0000000000000000
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CapInh: 00000000fffffeff
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CapPrm: 0000000000000000
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CapEff: 0000000000000000
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CapBnd: ffffffffffffffff
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voluntary_ctxt_switches: 0
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nonvoluntary_ctxt_switches: 1
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This shows you nearly the same information you would get if you viewed it with
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the ps command. In fact, ps uses the proc file system to obtain its
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information. But you get a more detailed view of the process by reading the
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file /proc/PID/status. It fields are described in table 1-2.
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The statm file contains more detailed information about the process
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memory usage. Its seven fields are explained in Table 1-3. The stat file
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contains details information about the process itself. Its fields are
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explained in Table 1-4.
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Table 1-2: Contents of the statm files (as of 2.6.30-rc7)
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..............................................................................
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Field Content
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Name filename of the executable
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State state (R is running, S is sleeping, D is sleeping
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in an uninterruptible wait, Z is zombie,
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T is traced or stopped)
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Tgid thread group ID
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Pid process id
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PPid process id of the parent process
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TracerPid PID of process tracing this process (0 if not)
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Uid Real, effective, saved set, and file system UIDs
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Gid Real, effective, saved set, and file system GIDs
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FDSize number of file descriptor slots currently allocated
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Groups supplementary group list
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VmPeak peak virtual memory size
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VmSize total program size
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VmLck locked memory size
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VmHWM peak resident set size ("high water mark")
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VmRSS size of memory portions
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VmData size of data, stack, and text segments
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VmStk size of data, stack, and text segments
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VmExe size of text segment
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VmLib size of shared library code
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VmPTE size of page table entries
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Threads number of threads
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SigQ number of signals queued/max. number for queue
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SigPnd bitmap of pending signals for the thread
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ShdPnd bitmap of shared pending signals for the process
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SigBlk bitmap of blocked signals
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SigIgn bitmap of ignored signals
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SigCgt bitmap of catched signals
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CapInh bitmap of inheritable capabilities
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CapPrm bitmap of permitted capabilities
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CapEff bitmap of effective capabilities
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CapBnd bitmap of capabilities bounding set
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Cpus_allowed mask of CPUs on which this process may run
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Cpus_allowed_list Same as previous, but in "list format"
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Mems_allowed mask of memory nodes allowed to this process
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Mems_allowed_list Same as previous, but in "list format"
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voluntary_ctxt_switches number of voluntary context switches
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nonvoluntary_ctxt_switches number of non voluntary context switches
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..............................................................................
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Table 1-3: Contents of the statm files (as of 2.6.8-rc3)
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..............................................................................
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Field Content
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size total program size (pages) (same as VmSize in status)
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resident size of memory portions (pages) (same as VmRSS in status)
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shared number of pages that are shared (i.e. backed by a file)
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trs number of pages that are 'code' (not including libs; broken,
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includes data segment)
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lrs number of pages of library (always 0 on 2.6)
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drs number of pages of data/stack (including libs; broken,
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includes library text)
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dt number of dirty pages (always 0 on 2.6)
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..............................................................................
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Table 1-4: Contents of the stat files (as of 2.6.30-rc7)
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..............................................................................
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Field Content
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pid process id
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tcomm filename of the executable
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state state (R is running, S is sleeping, D is sleeping in an
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uninterruptible wait, Z is zombie, T is traced or stopped)
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ppid process id of the parent process
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pgrp pgrp of the process
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sid session id
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tty_nr tty the process uses
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tty_pgrp pgrp of the tty
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flags task flags
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min_flt number of minor faults
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cmin_flt number of minor faults with child's
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maj_flt number of major faults
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cmaj_flt number of major faults with child's
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utime user mode jiffies
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stime kernel mode jiffies
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cutime user mode jiffies with child's
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cstime kernel mode jiffies with child's
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priority priority level
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nice nice level
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num_threads number of threads
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it_real_value (obsolete, always 0)
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start_time time the process started after system boot
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vsize virtual memory size
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rss resident set memory size
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rsslim current limit in bytes on the rss
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start_code address above which program text can run
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end_code address below which program text can run
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start_stack address of the start of the stack
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esp current value of ESP
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eip current value of EIP
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pending bitmap of pending signals
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blocked bitmap of blocked signals
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sigign bitmap of ignored signals
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sigcatch bitmap of catched signals
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wchan address where process went to sleep
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0 (place holder)
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0 (place holder)
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exit_signal signal to send to parent thread on exit
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task_cpu which CPU the task is scheduled on
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rt_priority realtime priority
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policy scheduling policy (man sched_setscheduler)
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blkio_ticks time spent waiting for block IO
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gtime guest time of the task in jiffies
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cgtime guest time of the task children in jiffies
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..............................................................................
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The /proc/PID/map file containing the currently mapped memory regions and
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their access permissions.
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The format is:
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address perms offset dev inode pathname
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08048000-08049000 r-xp 00000000 03:00 8312 /opt/test
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08049000-0804a000 rw-p 00001000 03:00 8312 /opt/test
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0804a000-0806b000 rw-p 00000000 00:00 0 [heap]
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a7cb1000-a7cb2000 ---p 00000000 00:00 0
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a7cb2000-a7eb2000 rw-p 00000000 00:00 0
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a7eb2000-a7eb3000 ---p 00000000 00:00 0
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a7eb3000-a7ed5000 rw-p 00000000 00:00 0
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a7ed5000-a8008000 r-xp 00000000 03:00 4222 /lib/libc.so.6
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a8008000-a800a000 r--p 00133000 03:00 4222 /lib/libc.so.6
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a800a000-a800b000 rw-p 00135000 03:00 4222 /lib/libc.so.6
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a800b000-a800e000 rw-p 00000000 00:00 0
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a800e000-a8022000 r-xp 00000000 03:00 14462 /lib/libpthread.so.0
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a8022000-a8023000 r--p 00013000 03:00 14462 /lib/libpthread.so.0
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a8023000-a8024000 rw-p 00014000 03:00 14462 /lib/libpthread.so.0
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a8024000-a8027000 rw-p 00000000 00:00 0
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a8027000-a8043000 r-xp 00000000 03:00 8317 /lib/ld-linux.so.2
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a8043000-a8044000 r--p 0001b000 03:00 8317 /lib/ld-linux.so.2
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a8044000-a8045000 rw-p 0001c000 03:00 8317 /lib/ld-linux.so.2
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aff35000-aff4a000 rw-p 00000000 00:00 0 [stack]
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ffffe000-fffff000 r-xp 00000000 00:00 0 [vdso]
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where "address" is the address space in the process that it occupies, "perms"
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is a set of permissions:
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r = read
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w = write
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x = execute
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s = shared
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p = private (copy on write)
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"offset" is the offset into the mapping, "dev" is the device (major:minor), and
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"inode" is the inode on that device. 0 indicates that no inode is associated
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with the memory region, as the case would be with BSS (uninitialized data).
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The "pathname" shows the name associated file for this mapping. If the mapping
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is not associated with a file:
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[heap] = the heap of the program
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[stack] = the stack of the main process
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[vdso] = the "virtual dynamic shared object",
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the kernel system call handler
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or if empty, the mapping is anonymous.
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The /proc/PID/smaps is an extension based on maps, showing the memory
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consumption for each of the process's mappings. For each of mappings there
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is a series of lines such as the following:
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08048000-080bc000 r-xp 00000000 03:02 13130 /bin/bash
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Size: 1084 kB
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Rss: 892 kB
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Pss: 374 kB
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Shared_Clean: 892 kB
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Shared_Dirty: 0 kB
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Private_Clean: 0 kB
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Private_Dirty: 0 kB
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Referenced: 892 kB
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Swap: 0 kB
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KernelPageSize: 4 kB
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MMUPageSize: 4 kB
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The first of these lines shows the same information as is displayed for the
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mapping in /proc/PID/maps. The remaining lines show the size of the mapping,
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the amount of the mapping that is currently resident in RAM, the "proportional
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set size” (divide each shared page by the number of processes sharing it), the
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number of clean and dirty shared pages in the mapping, and the number of clean
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and dirty private pages in the mapping. The "Referenced" indicates the amount
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of memory currently marked as referenced or accessed.
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This file is only present if the CONFIG_MMU kernel configuration option is
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enabled.
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1.2 Kernel data
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---------------
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Similar to the process entries, the kernel data files give information about
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the running kernel. The files used to obtain this information are contained in
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/proc and are listed in Table 1-5. Not all of these will be present in your
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system. It depends on the kernel configuration and the loaded modules, which
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files are there, and which are missing.
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Table 1-5: Kernel info in /proc
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..............................................................................
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File Content
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apm Advanced power management info
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buddyinfo Kernel memory allocator information (see text) (2.5)
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bus Directory containing bus specific information
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cmdline Kernel command line
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cpuinfo Info about the CPU
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devices Available devices (block and character)
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dma Used DMS channels
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filesystems Supported filesystems
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driver Various drivers grouped here, currently rtc (2.4)
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execdomains Execdomains, related to security (2.4)
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fb Frame Buffer devices (2.4)
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fs File system parameters, currently nfs/exports (2.4)
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ide Directory containing info about the IDE subsystem
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interrupts Interrupt usage
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iomem Memory map (2.4)
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ioports I/O port usage
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irq Masks for irq to cpu affinity (2.4)(smp?)
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isapnp ISA PnP (Plug&Play) Info (2.4)
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kcore Kernel core image (can be ELF or A.OUT(deprecated in 2.4))
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kmsg Kernel messages
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ksyms Kernel symbol table
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loadavg Load average of last 1, 5 & 15 minutes
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locks Kernel locks
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meminfo Memory info
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misc Miscellaneous
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modules List of loaded modules
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mounts Mounted filesystems
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net Networking info (see text)
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partitions Table of partitions known to the system
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pci Deprecated info of PCI bus (new way -> /proc/bus/pci/,
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decoupled by lspci (2.4)
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rtc Real time clock
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scsi SCSI info (see text)
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slabinfo Slab pool info
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softirqs softirq usage
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stat Overall statistics
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swaps Swap space utilization
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sys See chapter 2
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sysvipc Info of SysVIPC Resources (msg, sem, shm) (2.4)
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tty Info of tty drivers
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uptime System uptime
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version Kernel version
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video bttv info of video resources (2.4)
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vmallocinfo Show vmalloced areas
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..............................................................................
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You can, for example, check which interrupts are currently in use and what
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they are used for by looking in the file /proc/interrupts:
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> cat /proc/interrupts
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CPU0
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0: 8728810 XT-PIC timer
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1: 895 XT-PIC keyboard
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2: 0 XT-PIC cascade
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3: 531695 XT-PIC aha152x
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4: 2014133 XT-PIC serial
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5: 44401 XT-PIC pcnet_cs
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8: 2 XT-PIC rtc
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11: 8 XT-PIC i82365
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12: 182918 XT-PIC PS/2 Mouse
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13: 1 XT-PIC fpu
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14: 1232265 XT-PIC ide0
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15: 7 XT-PIC ide1
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NMI: 0
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In 2.4.* a couple of lines where added to this file LOC & ERR (this time is the
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output of a SMP machine):
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> cat /proc/interrupts
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CPU0 CPU1
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0: 1243498 1214548 IO-APIC-edge timer
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1: 8949 8958 IO-APIC-edge keyboard
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2: 0 0 XT-PIC cascade
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5: 11286 10161 IO-APIC-edge soundblaster
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8: 1 0 IO-APIC-edge rtc
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9: 27422 27407 IO-APIC-edge 3c503
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12: 113645 113873 IO-APIC-edge PS/2 Mouse
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13: 0 0 XT-PIC fpu
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14: 22491 24012 IO-APIC-edge ide0
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15: 2183 2415 IO-APIC-edge ide1
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17: 30564 30414 IO-APIC-level eth0
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18: 177 164 IO-APIC-level bttv
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NMI: 2457961 2457959
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LOC: 2457882 2457881
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ERR: 2155
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NMI is incremented in this case because every timer interrupt generates a NMI
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(Non Maskable Interrupt) which is used by the NMI Watchdog to detect lockups.
|
|
|
|
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 2.6.2* /proc/interrupts was expanded again. This time the goal was for
|
|
/proc/interrupts to display every IRQ vector in use by the system, not
|
|
just those considered 'most important'. The new vectors are:
|
|
|
|
THR -- interrupt raised when a machine check threshold counter
|
|
(typically counting ECC corrected errors of memory or cache) exceeds
|
|
a configurable threshold. Only available on some systems.
|
|
|
|
TRM -- a thermal event interrupt occurs when a temperature threshold
|
|
has been exceeded for the CPU. This interrupt may also be generated
|
|
when the temperature drops back to normal.
|
|
|
|
SPU -- a spurious interrupt is some interrupt that was raised then lowered
|
|
by some IO device before it could be fully processed by the APIC. Hence
|
|
the APIC sees the interrupt but does not know what device it came from.
|
|
For this case the APIC will generate the interrupt with a IRQ vector
|
|
of 0xff. This might also be generated by chipset bugs.
|
|
|
|
RES, CAL, TLB -- rescheduling, call and TLB flush interrupts are
|
|
sent from one CPU to another per the needs of the OS. Typically,
|
|
their statistics are used by kernel developers and interested users to
|
|
determine the occurrence of interrupts of the given type.
|
|
|
|
The above IRQ vectors are displayed only when relevent. For example,
|
|
the threshold vector does not exist on x86_64 platforms. Others are
|
|
suppressed when the system is a uniprocessor. As of this writing, only
|
|
i386 and x86_64 platforms support the new IRQ vector displays.
|
|
|
|
Of some interest is the introduction of the /proc/irq directory to 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 two files; default_smp_affinity and
|
|
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 default_smp_affinity
|
|
> ls /proc/irq/0/
|
|
smp_affinity
|
|
|
|
smp_affinity is a bitmask, in which you can specify which CPUs can handle the
|
|
IRQ, you can set it by doing:
|
|
|
|
> echo 1 > /proc/irq/10/smp_affinity
|
|
|
|
This means that only the first CPU will handle the IRQ, but you can also echo
|
|
5 which means that only the first and fourth CPU can handle the IRQ.
|
|
|
|
The contents of each smp_affinity file is the same by default:
|
|
|
|
> cat /proc/irq/0/smp_affinity
|
|
ffffffff
|
|
|
|
The default_smp_affinity mask applies to all non-active IRQs, which are the
|
|
IRQs which have not yet been allocated/activated, and hence which lack a
|
|
/proc/irq/[0-9]* directory.
|
|
|
|
prof_cpu_mask specifies which CPUs are to be profiled by the system wide
|
|
profiler. Default value is ffffffff (all cpus).
|
|
|
|
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.
|
|
Linux uses slab pools for memory management above page level in version 2.2.
|
|
Commonly used objects have their own slab pool (such as network buffers,
|
|
directory cache, and so on).
|
|
|
|
..............................................................................
|
|
|
|
> cat /proc/buddyinfo
|
|
|
|
Node 0, zone DMA 0 4 5 4 4 3 ...
|
|
Node 0, zone Normal 1 0 0 1 101 8 ...
|
|
Node 0, zone HighMem 2 0 0 1 1 0 ...
|
|
|
|
Memory fragmentation is a problem under some workloads, and buddyinfo is a
|
|
useful tool for helping diagnose these problems. Buddyinfo will give you a
|
|
clue as to how big an area you can safely allocate, or why a previous
|
|
allocation failed.
|
|
|
|
Each column represents the number of pages of a certain order which are
|
|
available. In this case, there are 0 chunks of 2^0*PAGE_SIZE available in
|
|
ZONE_DMA, 4 chunks of 2^1*PAGE_SIZE in ZONE_DMA, 101 chunks of 2^4*PAGE_SIZE
|
|
available in ZONE_NORMAL, etc...
|
|
|
|
..............................................................................
|
|
|
|
meminfo:
|
|
|
|
Provides information about distribution and utilization of memory. This
|
|
varies by architecture and compile options. The following is from a
|
|
16GB PIII, which has highmem enabled. You may not have all of these fields.
|
|
|
|
> cat /proc/meminfo
|
|
|
|
|
|
MemTotal: 16344972 kB
|
|
MemFree: 13634064 kB
|
|
Buffers: 3656 kB
|
|
Cached: 1195708 kB
|
|
SwapCached: 0 kB
|
|
Active: 891636 kB
|
|
Inactive: 1077224 kB
|
|
HighTotal: 15597528 kB
|
|
HighFree: 13629632 kB
|
|
LowTotal: 747444 kB
|
|
LowFree: 4432 kB
|
|
SwapTotal: 0 kB
|
|
SwapFree: 0 kB
|
|
Dirty: 968 kB
|
|
Writeback: 0 kB
|
|
AnonPages: 861800 kB
|
|
Mapped: 280372 kB
|
|
Slab: 284364 kB
|
|
SReclaimable: 159856 kB
|
|
SUnreclaim: 124508 kB
|
|
PageTables: 24448 kB
|
|
NFS_Unstable: 0 kB
|
|
Bounce: 0 kB
|
|
WritebackTmp: 0 kB
|
|
CommitLimit: 7669796 kB
|
|
Committed_AS: 100056 kB
|
|
VmallocTotal: 112216 kB
|
|
VmallocUsed: 428 kB
|
|
VmallocChunk: 111088 kB
|
|
|
|
MemTotal: Total usable ram (i.e. physical ram minus a few reserved
|
|
bits and the kernel binary code)
|
|
MemFree: The sum of LowFree+HighFree
|
|
Buffers: Relatively temporary storage for raw disk blocks
|
|
shouldn't get tremendously large (20MB or so)
|
|
Cached: in-memory cache for files read from the disk (the
|
|
pagecache). Doesn't include SwapCached
|
|
SwapCached: Memory that once was swapped out, is swapped back in but
|
|
still also is in the swapfile (if memory is needed it
|
|
doesn't need to be swapped out AGAIN because it is already
|
|
in the swapfile. This saves I/O)
|
|
Active: Memory that has been used more recently and usually not
|
|
reclaimed unless absolutely necessary.
|
|
Inactive: Memory which has been less recently used. It is more
|
|
eligible to be reclaimed for other purposes
|
|
HighTotal:
|
|
HighFree: Highmem is all memory above ~860MB of physical memory
|
|
Highmem areas are for use by userspace programs, or
|
|
for the pagecache. The kernel must use tricks to access
|
|
this memory, making it slower to access than lowmem.
|
|
LowTotal:
|
|
LowFree: Lowmem is memory which can be used for everything that
|
|
highmem can be used for, but it is also available for the
|
|
kernel's use for its own data structures. Among many
|
|
other things, it is where everything from the Slab is
|
|
allocated. Bad things happen when you're out of lowmem.
|
|
SwapTotal: total amount of swap space available
|
|
SwapFree: Memory which has been evicted from RAM, and is temporarily
|
|
on the disk
|
|
Dirty: Memory which is waiting to get written back to the disk
|
|
Writeback: Memory which is actively being written back to the disk
|
|
AnonPages: Non-file backed pages mapped into userspace page tables
|
|
Mapped: files which have been mmaped, such as libraries
|
|
Slab: in-kernel data structures cache
|
|
SReclaimable: Part of Slab, that might be reclaimed, such as caches
|
|
SUnreclaim: Part of Slab, that cannot be reclaimed on memory pressure
|
|
PageTables: amount of memory dedicated to the lowest level of page
|
|
tables.
|
|
NFS_Unstable: NFS pages sent to the server, but not yet committed to stable
|
|
storage
|
|
Bounce: Memory used for block device "bounce buffers"
|
|
WritebackTmp: Memory used by FUSE for temporary writeback buffers
|
|
CommitLimit: Based on the overcommit ratio ('vm.overcommit_ratio'),
|
|
this is the total amount of memory currently available to
|
|
be allocated on the system. This limit is only adhered to
|
|
if strict overcommit accounting is enabled (mode 2 in
|
|
'vm.overcommit_memory').
|
|
The CommitLimit is calculated with the following formula:
|
|
CommitLimit = ('vm.overcommit_ratio' * Physical RAM) + Swap
|
|
For example, on a system with 1G of physical RAM and 7G
|
|
of swap with a `vm.overcommit_ratio` of 30 it would
|
|
yield a CommitLimit of 7.3G.
|
|
For more details, see the memory overcommit documentation
|
|
in vm/overcommit-accounting.
|
|
Committed_AS: The amount of memory presently allocated on the system.
|
|
The committed memory is a sum of all of the memory which
|
|
has been allocated by processes, even if it has not been
|
|
"used" by them as of yet. A process which malloc()'s 1G
|
|
of memory, but only touches 300M of it will only show up
|
|
as using 300M of memory even if it has the address space
|
|
allocated for the entire 1G. This 1G is memory which has
|
|
been "committed" to by the VM and can be used at any time
|
|
by the allocating application. With strict overcommit
|
|
enabled on the system (mode 2 in 'vm.overcommit_memory'),
|
|
allocations which would exceed the CommitLimit (detailed
|
|
above) will not be permitted. This is useful if one needs
|
|
to guarantee that processes will not fail due to lack of
|
|
memory once that memory has been successfully allocated.
|
|
VmallocTotal: total size of vmalloc memory area
|
|
VmallocUsed: amount of vmalloc area which is used
|
|
VmallocChunk: largest contiguous block of vmalloc area which is free
|
|
|
|
..............................................................................
|
|
|
|
vmallocinfo:
|
|
|
|
Provides information about vmalloced/vmaped areas. One line per area,
|
|
containing the virtual address range of the area, size in bytes,
|
|
caller information of the creator, and optional information depending
|
|
on the kind of area :
|
|
|
|
pages=nr number of pages
|
|
phys=addr if a physical address was specified
|
|
ioremap I/O mapping (ioremap() and friends)
|
|
vmalloc vmalloc() area
|
|
vmap vmap()ed pages
|
|
user VM_USERMAP area
|
|
vpages buffer for pages pointers was vmalloced (huge area)
|
|
N<node>=nr (Only on NUMA kernels)
|
|
Number of pages allocated on memory node <node>
|
|
|
|
> cat /proc/vmallocinfo
|
|
0xffffc20000000000-0xffffc20000201000 2101248 alloc_large_system_hash+0x204 ...
|
|
/0x2c0 pages=512 vmalloc N0=128 N1=128 N2=128 N3=128
|
|
0xffffc20000201000-0xffffc20000302000 1052672 alloc_large_system_hash+0x204 ...
|
|
/0x2c0 pages=256 vmalloc N0=64 N1=64 N2=64 N3=64
|
|
0xffffc20000302000-0xffffc20000304000 8192 acpi_tb_verify_table+0x21/0x4f...
|
|
phys=7fee8000 ioremap
|
|
0xffffc20000304000-0xffffc20000307000 12288 acpi_tb_verify_table+0x21/0x4f...
|
|
phys=7fee7000 ioremap
|
|
0xffffc2000031d000-0xffffc2000031f000 8192 init_vdso_vars+0x112/0x210
|
|
0xffffc2000031f000-0xffffc2000032b000 49152 cramfs_uncompress_init+0x2e ...
|
|
/0x80 pages=11 vmalloc N0=3 N1=3 N2=2 N3=3
|
|
0xffffc2000033a000-0xffffc2000033d000 12288 sys_swapon+0x640/0xac0 ...
|
|
pages=2 vmalloc N1=2
|
|
0xffffc20000347000-0xffffc2000034c000 20480 xt_alloc_table_info+0xfe ...
|
|
/0x130 [x_tables] pages=4 vmalloc N0=4
|
|
0xffffffffa0000000-0xffffffffa000f000 61440 sys_init_module+0xc27/0x1d00 ...
|
|
pages=14 vmalloc N2=14
|
|
0xffffffffa000f000-0xffffffffa0014000 20480 sys_init_module+0xc27/0x1d00 ...
|
|
pages=4 vmalloc N1=4
|
|
0xffffffffa0014000-0xffffffffa0017000 12288 sys_init_module+0xc27/0x1d00 ...
|
|
pages=2 vmalloc N1=2
|
|
0xffffffffa0017000-0xffffffffa0022000 45056 sys_init_module+0xc27/0x1d00 ...
|
|
pages=10 vmalloc N0=10
|
|
|
|
..............................................................................
|
|
|
|
softirqs:
|
|
|
|
Provides counts of softirq handlers serviced since boot time, for each cpu.
|
|
|
|
> cat /proc/softirqs
|
|
CPU0 CPU1 CPU2 CPU3
|
|
HI: 0 0 0 0
|
|
TIMER: 27166 27120 27097 27034
|
|
NET_TX: 0 0 0 17
|
|
NET_RX: 42 0 0 39
|
|
BLOCK: 0 0 107 1121
|
|
TASKLET: 0 0 0 290
|
|
SCHED: 27035 26983 26971 26746
|
|
HRTIMER: 0 0 0 0
|
|
RCU: 1678 1769 2178 2250
|
|
|
|
|
|
1.3 IDE devices in /proc/ide
|
|
----------------------------
|
|
|
|
The subdirectory /proc/ide contains information about all IDE devices of which
|
|
the kernel is aware. There is one subdirectory for each IDE controller, the
|
|
file drivers and a link for each IDE device, pointing to the device directory
|
|
in the controller specific subtree.
|
|
|
|
The file drivers contains general information about the drivers used for the
|
|
IDE devices:
|
|
|
|
> cat /proc/ide/drivers
|
|
ide-cdrom version 4.53
|
|
ide-disk version 1.08
|
|
|
|
More detailed information can be found in the controller specific
|
|
subdirectories. These are named ide0, ide1 and so on. Each of these
|
|
directories contains the files shown in table 1-6.
|
|
|
|
|
|
Table 1-6: IDE controller info in /proc/ide/ide?
|
|
..............................................................................
|
|
File Content
|
|
channel IDE channel (0 or 1)
|
|
config Configuration (only for PCI/IDE bridge)
|
|
mate Mate name
|
|
model Type/Chipset of IDE controller
|
|
..............................................................................
|
|
|
|
Each device connected to a controller has a separate subdirectory in the
|
|
controllers directory. The files listed in table 1-7 are contained in these
|
|
directories.
|
|
|
|
|
|
Table 1-7: IDE device information
|
|
..............................................................................
|
|
File Content
|
|
cache The cache
|
|
capacity Capacity of the medium (in 512Byte blocks)
|
|
driver driver and version
|
|
geometry physical and logical geometry
|
|
identify device identify block
|
|
media media type
|
|
model device identifier
|
|
settings device setup
|
|
smart_thresholds IDE disk management thresholds
|
|
smart_values IDE disk management values
|
|
..............................................................................
|
|
|
|
The most interesting file is settings. This file contains a nice overview of
|
|
the drive parameters:
|
|
|
|
# cat /proc/ide/ide0/hda/settings
|
|
name value min max mode
|
|
---- ----- --- --- ----
|
|
bios_cyl 526 0 65535 rw
|
|
bios_head 255 0 255 rw
|
|
bios_sect 63 0 63 rw
|
|
breada_readahead 4 0 127 rw
|
|
bswap 0 0 1 r
|
|
file_readahead 72 0 2097151 rw
|
|
io_32bit 0 0 3 rw
|
|
keepsettings 0 0 1 rw
|
|
max_kb_per_request 122 1 127 rw
|
|
multcount 0 0 8 rw
|
|
nice1 1 0 1 rw
|
|
nowerr 0 0 1 rw
|
|
pio_mode write-only 0 255 w
|
|
slow 0 0 1 rw
|
|
unmaskirq 0 0 1 rw
|
|
using_dma 0 0 1 rw
|
|
|
|
|
|
1.4 Networking info in /proc/net
|
|
--------------------------------
|
|
|
|
The subdirectory /proc/net follows the usual pattern. Table 1-8 shows the
|
|
additional values you get for IP version 6 if you configure the kernel to
|
|
support this. Table 1-9 lists the files and their meaning.
|
|
|
|
|
|
Table 1-8: IPv6 info in /proc/net
|
|
..............................................................................
|
|
File Content
|
|
udp6 UDP sockets (IPv6)
|
|
tcp6 TCP sockets (IPv6)
|
|
raw6 Raw device statistics (IPv6)
|
|
igmp6 IP multicast addresses, which this host joined (IPv6)
|
|
if_inet6 List of IPv6 interface addresses
|
|
ipv6_route Kernel routing table for IPv6
|
|
rt6_stats Global IPv6 routing tables statistics
|
|
sockstat6 Socket statistics (IPv6)
|
|
snmp6 Snmp data (IPv6)
|
|
..............................................................................
|
|
|
|
|
|
Table 1-9: Network info in /proc/net
|
|
..............................................................................
|
|
File Content
|
|
arp Kernel ARP table
|
|
dev network devices with statistics
|
|
dev_mcast the Layer2 multicast groups a device is listening too
|
|
(interface index, label, number of references, number of bound
|
|
addresses).
|
|
dev_stat network device status
|
|
ip_fwchains Firewall chain linkage
|
|
ip_fwnames Firewall chain names
|
|
ip_masq Directory containing the masquerading tables
|
|
ip_masquerade Major masquerading table
|
|
netstat Network statistics
|
|
raw raw device statistics
|
|
route Kernel routing table
|
|
rpc Directory containing rpc info
|
|
rt_cache Routing cache
|
|
snmp SNMP data
|
|
sockstat Socket statistics
|
|
tcp TCP sockets
|
|
tr_rif Token ring RIF routing table
|
|
udp UDP sockets
|
|
unix UNIX domain sockets
|
|
wireless Wireless interface data (Wavelan etc)
|
|
igmp IP multicast addresses, which this host joined
|
|
psched Global packet scheduler parameters.
|
|
netlink List of PF_NETLINK sockets
|
|
ip_mr_vifs List of multicast virtual interfaces
|
|
ip_mr_cache List of multicast routing cache
|
|
..............................................................................
|
|
|
|
You can use this information to see which network devices are available in
|
|
your system and how much traffic was routed over those devices:
|
|
|
|
> cat /proc/net/dev
|
|
Inter-|Receive |[...
|
|
face |bytes packets errs drop fifo frame compressed multicast|[...
|
|
lo: 908188 5596 0 0 0 0 0 0 [...
|
|
ppp0:15475140 20721 410 0 0 410 0 0 [...
|
|
eth0: 614530 7085 0 0 0 0 0 1 [...
|
|
|
|
...] Transmit
|
|
...] bytes packets errs drop fifo colls carrier compressed
|
|
...] 908188 5596 0 0 0 0 0 0
|
|
...] 1375103 17405 0 0 0 0 0 0
|
|
...] 1703981 5535 0 0 0 3 0 0
|
|
|
|
In addition, each Channel Bond interface has it's own directory. For
|
|
example, the bond0 device will have a directory called /proc/net/bond0/.
|
|
It will contain information that is specific to that bond, such as the
|
|
current slaves of the bond, the link status of the slaves, and how
|
|
many times the slaves link has failed.
|
|
|
|
1.5 SCSI info
|
|
-------------
|
|
|
|
If you have a SCSI host adapter in your system, you'll find a subdirectory
|
|
named after the driver for this adapter in /proc/scsi. You'll also see a list
|
|
of all recognized SCSI devices in /proc/scsi:
|
|
|
|
>cat /proc/scsi/scsi
|
|
Attached devices:
|
|
Host: scsi0 Channel: 00 Id: 00 Lun: 00
|
|
Vendor: IBM Model: DGHS09U Rev: 03E0
|
|
Type: Direct-Access ANSI SCSI revision: 03
|
|
Host: scsi0 Channel: 00 Id: 06 Lun: 00
|
|
Vendor: PIONEER Model: CD-ROM DR-U06S Rev: 1.04
|
|
Type: CD-ROM ANSI SCSI revision: 02
|
|
|
|
|
|
The directory named after the driver has one file for each adapter found in
|
|
the system. These files contain information about the controller, including
|
|
the used IRQ and the IO address range. The amount of information shown is
|
|
dependent on the adapter you use. The example shows the output for an Adaptec
|
|
AHA-2940 SCSI adapter:
|
|
|
|
> cat /proc/scsi/aic7xxx/0
|
|
|
|
Adaptec AIC7xxx driver version: 5.1.19/3.2.4
|
|
Compile Options:
|
|
TCQ Enabled By Default : Disabled
|
|
AIC7XXX_PROC_STATS : Disabled
|
|
AIC7XXX_RESET_DELAY : 5
|
|
Adapter Configuration:
|
|
SCSI Adapter: Adaptec AHA-294X Ultra SCSI host adapter
|
|
Ultra Wide Controller
|
|
PCI MMAPed I/O Base: 0xeb001000
|
|
Adapter SEEPROM Config: SEEPROM found and used.
|
|
Adaptec SCSI BIOS: Enabled
|
|
IRQ: 10
|
|
SCBs: Active 0, Max Active 2,
|
|
Allocated 15, HW 16, Page 255
|
|
Interrupts: 160328
|
|
BIOS Control Word: 0x18b6
|
|
Adapter Control Word: 0x005b
|
|
Extended Translation: Enabled
|
|
Disconnect Enable Flags: 0xffff
|
|
Ultra Enable Flags: 0x0001
|
|
Tag Queue Enable Flags: 0x0000
|
|
Ordered Queue Tag Flags: 0x0000
|
|
Default Tag Queue Depth: 8
|
|
Tagged Queue By Device array for aic7xxx host instance 0:
|
|
{255,255,255,255,255,255,255,255,255,255,255,255,255,255,255,255}
|
|
Actual queue depth per device for aic7xxx host instance 0:
|
|
{1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1}
|
|
Statistics:
|
|
(scsi0:0:0:0)
|
|
Device using Wide/Sync transfers at 40.0 MByte/sec, offset 8
|
|
Transinfo settings: current(12/8/1/0), goal(12/8/1/0), user(12/15/1/0)
|
|
Total transfers 160151 (74577 reads and 85574 writes)
|
|
(scsi0:0:6:0)
|
|
Device using Narrow/Sync transfers at 5.0 MByte/sec, offset 15
|
|
Transinfo settings: current(50/15/0/0), goal(50/15/0/0), user(50/15/0/0)
|
|
Total transfers 0 (0 reads and 0 writes)
|
|
|
|
|
|
1.6 Parallel port info in /proc/parport
|
|
---------------------------------------
|
|
|
|
The directory /proc/parport contains information about the parallel ports of
|
|
your system. It has one subdirectory for each port, named after the port
|
|
number (0,1,2,...).
|
|
|
|
These directories contain the four files shown in Table 1-10.
|
|
|
|
|
|
Table 1-10: Files in /proc/parport
|
|
..............................................................................
|
|
File Content
|
|
autoprobe Any IEEE-1284 device ID information that has been acquired.
|
|
devices list of the device drivers using that port. A + will appear by the
|
|
name of the device currently using the port (it might not appear
|
|
against any).
|
|
hardware Parallel port's base address, IRQ line and DMA channel.
|
|
irq IRQ that parport is using for that port. This is in a separate
|
|
file to allow you to alter it by writing a new value in (IRQ
|
|
number or none).
|
|
..............................................................................
|
|
|
|
1.7 TTY info in /proc/tty
|
|
-------------------------
|
|
|
|
Information about the available and actually used tty's can be found in the
|
|
directory /proc/tty.You'll find entries for drivers and line disciplines in
|
|
this directory, as shown in Table 1-11.
|
|
|
|
|
|
Table 1-11: Files in /proc/tty
|
|
..............................................................................
|
|
File Content
|
|
drivers list of drivers and their usage
|
|
ldiscs registered line disciplines
|
|
driver/serial usage statistic and status of single tty lines
|
|
..............................................................................
|
|
|
|
To see which tty's are currently in use, you can simply look into the file
|
|
/proc/tty/drivers:
|
|
|
|
> cat /proc/tty/drivers
|
|
pty_slave /dev/pts 136 0-255 pty:slave
|
|
pty_master /dev/ptm 128 0-255 pty:master
|
|
pty_slave /dev/ttyp 3 0-255 pty:slave
|
|
pty_master /dev/pty 2 0-255 pty:master
|
|
serial /dev/cua 5 64-67 serial:callout
|
|
serial /dev/ttyS 4 64-67 serial
|
|
/dev/tty0 /dev/tty0 4 0 system:vtmaster
|
|
/dev/ptmx /dev/ptmx 5 2 system
|
|
/dev/console /dev/console 5 1 system:console
|
|
/dev/tty /dev/tty 5 0 system:/dev/tty
|
|
unknown /dev/tty 4 1-63 console
|
|
|
|
|
|
1.8 Miscellaneous kernel statistics in /proc/stat
|
|
-------------------------------------------------
|
|
|
|
Various pieces of information about kernel activity are available in the
|
|
/proc/stat file. All of the numbers reported in this file are aggregates
|
|
since the system first booted. For a quick look, simply cat the file:
|
|
|
|
> cat /proc/stat
|
|
cpu 2255 34 2290 22625563 6290 127 456 0
|
|
cpu0 1132 34 1441 11311718 3675 127 438 0
|
|
cpu1 1123 0 849 11313845 2614 0 18 0
|
|
intr 114930548 113199788 3 0 5 263 0 4 [... lots more numbers ...]
|
|
ctxt 1990473
|
|
btime 1062191376
|
|
processes 2915
|
|
procs_running 1
|
|
procs_blocked 0
|
|
softirq 183433 0 21755 12 39 1137 231 21459 2263
|
|
|
|
The very first "cpu" line aggregates the numbers in all of the other "cpuN"
|
|
lines. These numbers identify the amount of time the CPU has spent performing
|
|
different kinds of work. Time units are in USER_HZ (typically hundredths of a
|
|
second). The meanings of the columns are as follows, from left to right:
|
|
|
|
- user: normal processes executing in user mode
|
|
- nice: niced processes executing in user mode
|
|
- system: processes executing in kernel mode
|
|
- idle: twiddling thumbs
|
|
- iowait: waiting for I/O to complete
|
|
- irq: servicing interrupts
|
|
- softirq: servicing softirqs
|
|
- steal: involuntary wait
|
|
|
|
The "intr" line gives counts of interrupts serviced since boot time, for each
|
|
of the possible system interrupts. The first column is the total of all
|
|
interrupts serviced; each subsequent column is the total for that particular
|
|
interrupt.
|
|
|
|
The "ctxt" line gives the total number of context switches across all CPUs.
|
|
|
|
The "btime" line gives the time at which the system booted, in seconds since
|
|
the Unix epoch.
|
|
|
|
The "processes" line gives the number of processes and threads created, which
|
|
includes (but is not limited to) those created by calls to the fork() and
|
|
clone() system calls.
|
|
|
|
The "procs_running" line gives the number of processes currently running on
|
|
CPUs.
|
|
|
|
The "procs_blocked" line gives the number of processes currently blocked,
|
|
waiting for I/O to complete.
|
|
|
|
The "softirq" line gives counts of softirqs serviced since boot time, for each
|
|
of the possible system softirqs. The first column is the total of all
|
|
softirqs serviced; each subsequent column is the total for that particular
|
|
softirq.
|
|
|
|
|
|
1.9 Ext4 file system parameters
|
|
------------------------------
|
|
|
|
Information about mounted ext4 file systems can be found in
|
|
/proc/fs/ext4. Each mounted filesystem will have a directory in
|
|
/proc/fs/ext4 based on its device name (i.e., /proc/fs/ext4/hdc or
|
|
/proc/fs/ext4/dm-0). The files in each per-device directory are shown
|
|
in Table 1-12, below.
|
|
|
|
Table 1-12: Files in /proc/fs/ext4/<devname>
|
|
..............................................................................
|
|
File Content
|
|
mb_groups details of multiblock allocator buddy cache of free blocks
|
|
mb_history multiblock allocation history
|
|
..............................................................................
|
|
|
|
|
|
------------------------------------------------------------------------------
|
|
Summary
|
|
------------------------------------------------------------------------------
|
|
The /proc file system serves information about the running system. It not only
|
|
allows access to process data but also allows you to request the kernel status
|
|
by reading files in the hierarchy.
|
|
|
|
The directory structure of /proc reflects the types of information and makes
|
|
it easy, if not obvious, where to look for specific data.
|
|
------------------------------------------------------------------------------
|
|
|
|
------------------------------------------------------------------------------
|
|
CHAPTER 2: MODIFYING SYSTEM PARAMETERS
|
|
------------------------------------------------------------------------------
|
|
|
|
------------------------------------------------------------------------------
|
|
In This Chapter
|
|
------------------------------------------------------------------------------
|
|
* Modifying kernel parameters by writing into files found in /proc/sys
|
|
* Exploring the files which modify certain parameters
|
|
* Review of the /proc/sys file tree
|
|
------------------------------------------------------------------------------
|
|
|
|
|
|
A very interesting part of /proc is the directory /proc/sys. This is not only
|
|
a source of information, it also allows you to change parameters within the
|
|
kernel. Be very careful when attempting this. You can optimize your system,
|
|
but you can also cause it to crash. Never alter kernel parameters on a
|
|
production system. Set up a development machine and test to make sure that
|
|
everything works the way you want it to. You may have no alternative but to
|
|
reboot the machine once an error has been made.
|
|
|
|
To change a value, simply echo the new value into the file. An example is
|
|
given below in the section on the file system data. You need to be root to do
|
|
this. You can create your own boot script to perform this every time your
|
|
system boots.
|
|
|
|
The files in /proc/sys can be used to fine tune and monitor miscellaneous and
|
|
general things in the operation of the Linux kernel. Since some of the files
|
|
can inadvertently disrupt your system, it is advisable to read both
|
|
documentation and source before actually making adjustments. In any case, be
|
|
very careful when writing to any of these files. The entries in /proc may
|
|
change slightly between the 2.1.* and the 2.2 kernel, so if there is any doubt
|
|
review the kernel documentation in the directory /usr/src/linux/Documentation.
|
|
This chapter is heavily based on the documentation included in the pre 2.2
|
|
kernels, and became part of it in version 2.2.1 of the Linux kernel.
|
|
|
|
Please see: Documentation/sysctls/ directory for descriptions of these
|
|
entries.
|
|
|
|
------------------------------------------------------------------------------
|
|
Summary
|
|
------------------------------------------------------------------------------
|
|
Certain aspects of kernel behavior can be modified at runtime, without the
|
|
need to recompile the kernel, or even to reboot the system. The files in the
|
|
/proc/sys tree can not only be read, but also modified. You can use the echo
|
|
command to write value into these files, thereby changing the default settings
|
|
of the kernel.
|
|
------------------------------------------------------------------------------
|
|
|
|
------------------------------------------------------------------------------
|
|
CHAPTER 3: PER-PROCESS PARAMETERS
|
|
------------------------------------------------------------------------------
|
|
|
|
3.1 /proc/<pid>/oom_adj - Adjust the oom-killer score
|
|
------------------------------------------------------
|
|
|
|
This file can be used to adjust the score used to select which processes should
|
|
be killed in an out-of-memory situation. The oom_adj value is a characteristic
|
|
of the task's mm, so all threads that share an mm with pid will have the same
|
|
oom_adj value. A high value will increase the likelihood of this process being
|
|
killed by the oom-killer. Valid values are in the range -16 to +15 as
|
|
explained below and a special value of -17, which disables oom-killing
|
|
altogether for threads sharing pid's mm.
|
|
|
|
The process to be killed in an out-of-memory situation is selected among all others
|
|
based on its badness score. This value equals the original memory size of the process
|
|
and is then updated according to its CPU time (utime + stime) and the
|
|
run time (uptime - start time). The longer it runs the smaller is the score.
|
|
Badness score is divided by the square root of the CPU time and then by
|
|
the double square root of the run time.
|
|
|
|
Swapped out tasks are killed first. Half of each child's memory size is added to
|
|
the parent's score if they do not share the same memory. Thus forking servers
|
|
are the prime candidates to be killed. Having only one 'hungry' child will make
|
|
parent less preferable than the child.
|
|
|
|
/proc/<pid>/oom_adj cannot be changed for kthreads since they are immune from
|
|
oom-killing already.
|
|
|
|
/proc/<pid>/oom_score shows process' current badness score.
|
|
|
|
The following heuristics are then applied:
|
|
* if the task was reniced, its score doubles
|
|
* superuser or direct hardware access tasks (CAP_SYS_ADMIN, CAP_SYS_RESOURCE
|
|
or CAP_SYS_RAWIO) have their score divided by 4
|
|
* if oom condition happened in one cpuset and checked task does not belong
|
|
to it, its score is divided by 8
|
|
* the resulting score is multiplied by two to the power of oom_adj, i.e.
|
|
points <<= oom_adj when it is positive and
|
|
points >>= -(oom_adj) otherwise
|
|
|
|
The task with the highest badness score is then selected and its children
|
|
are killed, process itself will be killed in an OOM situation when it does
|
|
not have children or some of them disabled oom like described above.
|
|
|
|
3.2 /proc/<pid>/oom_score - Display current oom-killer score
|
|
-------------------------------------------------------------
|
|
|
|
This file can be used to check the current score used by the oom-killer is for
|
|
any given <pid>. Use it together with /proc/<pid>/oom_adj to tune which
|
|
process should be killed in an out-of-memory situation.
|
|
|
|
|
|
3.3 /proc/<pid>/io - Display the IO accounting fields
|
|
-------------------------------------------------------
|
|
|
|
This file contains IO statistics for each running process
|
|
|
|
Example
|
|
-------
|
|
|
|
test:/tmp # dd if=/dev/zero of=/tmp/test.dat &
|
|
[1] 3828
|
|
|
|
test:/tmp # cat /proc/3828/io
|
|
rchar: 323934931
|
|
wchar: 323929600
|
|
syscr: 632687
|
|
syscw: 632675
|
|
read_bytes: 0
|
|
write_bytes: 323932160
|
|
cancelled_write_bytes: 0
|
|
|
|
|
|
Description
|
|
-----------
|
|
|
|
rchar
|
|
-----
|
|
|
|
I/O counter: chars read
|
|
The number of bytes which this task has caused to be read from storage. This
|
|
is simply the sum of bytes which this process passed to read() and pread().
|
|
It includes things like tty IO and it is unaffected by whether or not actual
|
|
physical disk IO was required (the read might have been satisfied from
|
|
pagecache)
|
|
|
|
|
|
wchar
|
|
-----
|
|
|
|
I/O counter: chars written
|
|
The number of bytes which this task has caused, or shall cause to be written
|
|
to disk. Similar caveats apply here as with rchar.
|
|
|
|
|
|
syscr
|
|
-----
|
|
|
|
I/O counter: read syscalls
|
|
Attempt to count the number of read I/O operations, i.e. syscalls like read()
|
|
and pread().
|
|
|
|
|
|
syscw
|
|
-----
|
|
|
|
I/O counter: write syscalls
|
|
Attempt to count the number of write I/O operations, i.e. syscalls like
|
|
write() and pwrite().
|
|
|
|
|
|
read_bytes
|
|
----------
|
|
|
|
I/O counter: bytes read
|
|
Attempt to count the number of bytes which this process really did cause to
|
|
be fetched from the storage layer. Done at the submit_bio() level, so it is
|
|
accurate for block-backed filesystems. <please add status regarding NFS and
|
|
CIFS at a later time>
|
|
|
|
|
|
write_bytes
|
|
-----------
|
|
|
|
I/O counter: bytes written
|
|
Attempt to count the number of bytes which this process caused to be sent to
|
|
the storage layer. This is done at page-dirtying time.
|
|
|
|
|
|
cancelled_write_bytes
|
|
---------------------
|
|
|
|
The big inaccuracy here is truncate. If a process writes 1MB to a file and
|
|
then deletes the file, it will in fact perform no writeout. But it will have
|
|
been accounted as having caused 1MB of write.
|
|
In other words: The number of bytes which this process caused to not happen,
|
|
by truncating pagecache. A task can cause "negative" IO too. If this task
|
|
truncates some dirty pagecache, some IO which another task has been accounted
|
|
for (in it's write_bytes) will not be happening. We _could_ just subtract that
|
|
from the truncating task's write_bytes, but there is information loss in doing
|
|
that.
|
|
|
|
|
|
Note
|
|
----
|
|
|
|
At its current implementation state, this is a bit racy on 32-bit machines: if
|
|
process A reads process B's /proc/pid/io while process B is updating one of
|
|
those 64-bit counters, process A could see an intermediate result.
|
|
|
|
|
|
More information about this can be found within the taskstats documentation in
|
|
Documentation/accounting.
|
|
|
|
3.4 /proc/<pid>/coredump_filter - Core dump filtering settings
|
|
---------------------------------------------------------------
|
|
When a process is dumped, all anonymous memory is written to a core file as
|
|
long as the size of the core file isn't limited. But sometimes we don't want
|
|
to dump some memory segments, for example, huge shared memory. Conversely,
|
|
sometimes we want to save file-backed memory segments into a core file, not
|
|
only the individual files.
|
|
|
|
/proc/<pid>/coredump_filter allows you to customize which memory segments
|
|
will be dumped when the <pid> process is dumped. coredump_filter is a bitmask
|
|
of memory types. If a bit of the bitmask is set, memory segments of the
|
|
corresponding memory type are dumped, otherwise they are not dumped.
|
|
|
|
The following 7 memory types are supported:
|
|
- (bit 0) anonymous private memory
|
|
- (bit 1) anonymous shared memory
|
|
- (bit 2) file-backed private memory
|
|
- (bit 3) file-backed shared memory
|
|
- (bit 4) ELF header pages in file-backed private memory areas (it is
|
|
effective only if the bit 2 is cleared)
|
|
- (bit 5) hugetlb private memory
|
|
- (bit 6) hugetlb shared memory
|
|
|
|
Note that MMIO pages such as frame buffer are never dumped and vDSO pages
|
|
are always dumped regardless of the bitmask status.
|
|
|
|
Note bit 0-4 doesn't effect any hugetlb memory. hugetlb memory are only
|
|
effected by bit 5-6.
|
|
|
|
Default value of coredump_filter is 0x23; this means all anonymous memory
|
|
segments and hugetlb private memory are dumped.
|
|
|
|
If you don't want to dump all shared memory segments attached to pid 1234,
|
|
write 0x21 to the process's proc file.
|
|
|
|
$ echo 0x21 > /proc/1234/coredump_filter
|
|
|
|
When a new process is created, the process inherits the bitmask status from its
|
|
parent. It is useful to set up coredump_filter before the program runs.
|
|
For example:
|
|
|
|
$ echo 0x7 > /proc/self/coredump_filter
|
|
$ ./some_program
|
|
|
|
3.5 /proc/<pid>/mountinfo - Information about mounts
|
|
--------------------------------------------------------
|
|
|
|
This file contains lines of the form:
|
|
|
|
36 35 98:0 /mnt1 /mnt2 rw,noatime master:1 - ext3 /dev/root rw,errors=continue
|
|
(1)(2)(3) (4) (5) (6) (7) (8) (9) (10) (11)
|
|
|
|
(1) mount ID: unique identifier of the mount (may be reused after umount)
|
|
(2) parent ID: ID of parent (or of self for the top of the mount tree)
|
|
(3) major:minor: value of st_dev for files on filesystem
|
|
(4) root: root of the mount within the filesystem
|
|
(5) mount point: mount point relative to the process's root
|
|
(6) mount options: per mount options
|
|
(7) optional fields: zero or more fields of the form "tag[:value]"
|
|
(8) separator: marks the end of the optional fields
|
|
(9) filesystem type: name of filesystem of the form "type[.subtype]"
|
|
(10) mount source: filesystem specific information or "none"
|
|
(11) super options: per super block options
|
|
|
|
Parsers should ignore all unrecognised optional fields. Currently the
|
|
possible optional fields are:
|
|
|
|
shared:X mount is shared in peer group X
|
|
master:X mount is slave to peer group X
|
|
propagate_from:X mount is slave and receives propagation from peer group X (*)
|
|
unbindable mount is unbindable
|
|
|
|
(*) X is the closest dominant peer group under the process's root. If
|
|
X is the immediate master of the mount, or if there's no dominant peer
|
|
group under the same root, then only the "master:X" field is present
|
|
and not the "propagate_from:X" field.
|
|
|
|
For more information on mount propagation see:
|
|
|
|
Documentation/filesystems/sharedsubtree.txt
|
|
|