Linux Process Information

Internal

• Linux
• Java Linux Memory
• Process Management Concepts

Overview

Consolidated information about all processes running on the system can be found in /proc/stat.

Information about an individual process can be found in /proc/<PID>/.

For system-level and user-level limits, see:

Linux Process Management Concepts

/proc/stat

This file contains consolidated information about all processes running on the system: counters for the total number of processes in the system, the number of running processes, number of blocked processes, etc.

cat /proc/stat
cpu  39570 0 ...
cpu0 10155 0 ...
cpu1 10019 0 ...
cpu2 9738 0 1...
cpu3 9656 0 ...
intr 2896032 82 ...
ctxt 4297127
btime 1492812098
processes 8713
procs_running 1
procs_blocked 0
softirq 1172895 0 ...

/proc/<PID>

/proc/<PID>/status

Contains synthetic information about the process:

Threads

Number of threads in process containing this thread.

...
Threads:	25
...

This is a script that reports the number of threads for a Java process:

bash script that reports the number of threads of a Java process

VmPeak

Peak virtual memory size.

VmSize

Virtual memory size.

VmLck

Locked memory size.

VmHWM

Peak resident set size ("high water mark").

VmRSS

Resident set size.

VmData, VmStk, VmExe

Size of data, stack, and text segments.

VmLib

Shared library code size.

VmPTE

Page table entries size (since Linux 2.6.10).

/proc/<PID>/stat

More details about the type of information found there can be obtained with man proc.

Also see:

Java Linux Memory

Contains status information about the process, on a single line. It is defined in /usr/src/linux/fs/proc/array.c.

Fields, in order, with their proper scanf(3) format specifiers:

1. pid %d

The process ID.

2. comm %s

The filename of the executable, in parentheses. This is visible whether or not the executable is swapped out.

3. state %c

One character from the string "RSDZTW" where R is running, S is sleeping in an interruptible wait, D is waiting in uninterruptible disk sleep, Z is zombie, T is traced or stopped (on a signal), and W is paging.

4. ppid %d

The PID of the parent.

5. pgrp %d

The process group ID of the process.

6. session %d

The session ID of the process.

7. tty_nr %d

The controlling terminal of the process. (The minor device number is contained in the combination of bits 31 to 20 and 7 to 0; the major device number is in bits 15 t0 8.)

8. tpgid %d

The ID of the foreground process group of the controlling terminal of the process.

9. flags %u (%lu before Linux 2.6.22)

The kernel flags word of the process. For bit meanings, see the PF_* defines in <linux/sched.h>. Details depend on the kernel version.

10. minflt %lu

The number of minor faults the process has made which have not required loading a memory page from disk.

11. cminflt %lu

The number of minor faults that the process's waited-for children have made.

12. majflt %lu

The number of major faults the process has made which have required loading a memory page from disk.

13. cmajflt %lu

The number of major faults that the process's waited-for children have made.

14. utime %lu

Amount of time that this process has been scheduled in user mode, measured in clock ticks (divide by sysconf(_SC_CLK_TCK). This includes guest time, guest_time (time spent running a virtual CPU, see below), so that applications that are not aware of the guest time field do not lose that time from their calculations.

15. stime %lu

Amount of time that this process has been scheduled in kernel mode, measured in clock ticks (divide by sysconf(_SC_CLK_TCK).

16. cutime %ld

Amount of time that this process's waited-for children have been scheduled in user mode, measured in clock ticks (divide by sysconf(_SC_CLK_TCK). (See also times(2).) This includes guest time, cguest_time (time spent running a virtual CPU, see below).

17. cstime %ld

Amount of time that this process's waited-for children have been scheduled in kernel mode, measured in clock ticks (divide by sysconf(_SC_CLK_TCK).

18. priority %ld

(Explanation for Linux 2.6) For processes running a real-time scheduling policy (policy below; see sched_setscheduler(2)), this is the negated scheduling priority, minus one; that is, a number in the range -2 to -100, corresponding to real-time priorities 1 to 99. For processes running under a non-real-time scheduling policy, this is the raw nice value (setpriority(2)) as represented in the kernel. The kernel stores nice values as numbers in the range 0 (high) to 39 (low), corresponding to the user-visible nice range of -20 to 19. Before Linux 2.6, this was a scaled value based on the scheduler weighting given to this process.

19. nice %ld

The nice value (see setpriority(2)), a value in the range 19 (low priority) to -20 (high priority).

20. num_threads %ld

Number of threads in this process (since Linux 2.6). Before kernel 2.6, this field was hard coded to 0 as a placeholder for an earlier removed field.

21. itrealvalue %ld

The time in jiffies before the next SIGALRM is sent to the process due to an interval timer. Since kernel 2.6.17, this field is no longer maintained, and is hard coded as 0.

22. starttime %llu (was %lu before Linux 2.6)

The time in jiffies the process started after system boot.

23. vsize %lu

Virtual memory size in bytes.

24. rss %ld

Resident Set Size: number of pages the process has in real memory. This is just the pages which count towards text, data, or stack space. This does not include pages which have not been demand-loaded in, or which are swapped out.

25. rsslim %lu

Current soft limit in bytes on the rss of the process; see the description of RLIMIT_RSS in getpriority(2).

26. startcode %lu

The address above which program text can run.

27. endcode %lu

The address below which program text can run.

28. startstack %lu

The address of the start (i.e., bottom) of the stack.

29. kstkesp %lu

The current value of ESP (stack pointer), as found in the kernel stack page for the process.

30. kstkeip %lu

The current EIP (instruction pointer).

31. signal %lu

The bitmap of pending signals, displayed as a decimal number. Obsolete, because it does not provide information on real-time signals; use /proc/[pid]/status instead.

32. blocked %lu

The bitmap of blocked signals, displayed as a decimal number. Obsolete, because it does not provide information on real-time signals; use /proc/[pid]/status instead.

33. sigignore %lu

The bitmap of ignored signals, displayed as a decimal number. Obsolete, because it does not provide information on real-time signals; use /proc/[pid]/status instead.

34. sigcatch %lu

The bitmap of caught signals, displayed as a decimal number. Obsolete, because it does not provide information on real-time signals; use /proc/[pid]/status instead.

35. wchan %lu

This is the "channel" in which the process is waiting. It is the address of a system call, and can be looked up in a namelist if you need a textual name. (If you have an up-to-date /etc/psdatabase, then try ps -l to see the WCHAN field in action.)

36. nswap %lu

Number of pages swapped (not maintained).

37. cnswap %lu

Cumulative nswap for child processes (not maintained).

38. exit_signal %d (since Linux 2.1.22)

Signal to be sent to parent when we die.

39. processor %d (since Linux 2.2.8)

CPU number last executed on.

40. rt_priority %u (since Linux 2.5.19; was %lu before Linux 2.6.22)

Real-time scheduling priority, a number in the range 1 to 99 for processes scheduled under a real-time policy, or 0, for non-real-time processes (see sched_setscheduler(2)).

41. policy %u (since Linux 2.5.19; was %lu before Linux 2.6.22)

Scheduling policy (see sched_setscheduler(2)). Decode using the SCHED_* constants in linux/sched.h.

42. delayacct_blkio_ticks %llu (since Linux 2.6.18)

Aggregated block I/O delays, measured in clock ticks (centiseconds).

43. guest_time %lu (since Linux 2.6.24)

Guest time of the process (time spent running a virtual CPU for a guest operating system), measured in clock ticks (divide by sysconf(_SC_CLK_TCK).

44. cguest_time %ld (since Linux 2.6.24)

Guest time of the process's children, measured in clock ticks (divide by sysconf(_SC_CLK_TCK).