Hi? Any idea what is the difference "cgroup.procs" entry and "tasks" entry of cgroup sysfs? both represent pid lists. I ran: cat /sys/fs/cgroup/cpuset/cgroup.procs and cat /sys/fs/cgroup/cpuset/tasks and entries of cgroup.procs appear in tasks. However there are many more tasks than cgroup.procs: cat /sys/fs/cgroup/cpuset/cgroup.procs | wc -l 153 cat /sys/fs/cgroup/cpuset/tasks | wc -l 383 Best Kevin
On Tue, Apr 02, 2013 at 05:54:56AM +0300, Kevin Wilson wrote:
Hi? Any idea what is the difference "cgroup.procs" entry and "tasks" entry of cgroup sysfs? both represent pid lists. I ran: cat /sys/fs/cgroup/cpuset/cgroup.procs and cat /sys/fs/cgroup/cpuset/tasks and entries of cgroup.procs appear in tasks.
However there are many more tasks than cgroup.procs:
cat /sys/fs/cgroup/cpuset/cgroup.procs | wc -l 153 cat /sys/fs/cgroup/cpuset/tasks | wc -l 383
The difference you are seeing is because there are some multithreaded processes in your cpuset. In the cgroup.procs file, each such process apears only once (listed by its TGID). In the tasks file, each thread appears once (listed by its PID). Check the pidlist_array_load function in kernel/cgroup.c. procs is a list of (unique) TGIDs, while tasks is a list of PIDs. Hope this helps, Vlad
Hi, Thanks a lot Vlad. This explains it. - Does anybody know of a ps command (or a filter to ps command) which will display only multithreaded processes (list processes by TGID) ? (I know now about the option of displaying cgroup.procs , but is something parallel can be done with ps ? ) rgs, Kevin On Tue, Apr 2, 2013 at 10:40 AM, Vlad Dogaru <ddvlad@herebedragons.ro> wrote:
On Tue, Apr 02, 2013 at 05:54:56AM +0300, Kevin Wilson wrote:
Hi? Any idea what is the difference "cgroup.procs" entry and "tasks" entry of cgroup sysfs? both represent pid lists. I ran: cat /sys/fs/cgroup/cpuset/cgroup.procs and cat /sys/fs/cgroup/cpuset/tasks and entries of cgroup.procs appear in tasks.
However there are many more tasks than cgroup.procs:
cat /sys/fs/cgroup/cpuset/cgroup.procs | wc -l 153 cat /sys/fs/cgroup/cpuset/tasks | wc -l 383
The difference you are seeing is because there are some multithreaded processes in your cpuset. In the cgroup.procs file, each such process apears only once (listed by its TGID). In the tasks file, each thread appears once (listed by its PID).
Check the pidlist_array_load function in kernel/cgroup.c. procs is a list of (unique) TGIDs, while tasks is a list of PIDs.
Hope this helps, Vlad
On Tue, 02 Apr 2013 16:46:24 +0300, Kevin Wilson said:
Hi, Thanks a lot Vlad. This explains it. - Does anybody know of a ps command (or a filter to ps command) which will display only multithreaded processes (list processes by TGID) ? (I know now about the option of displaying cgroup.procs , but is something parallel can be done with ps ? )
Have you tried 'ps -m' and friends? Though it doesn't do exactly what you wanted and *only* display multithreaded, you need to do some post-processing: $ ps max ... 928 ? - 0:00 /sbin/auditd -n - - S<sl 0:00 - - - S<sl 0:00 - 940 ? - 0:00 /sbin/audispd - - S<sl 0:00 - - - S<sl 0:00 - 951 ? - 0:00 /usr/sbin/abrtd -d -s - - Ss 0:00 - 960 ? - 0:00 /usr/bin/abrt-watch-log -F Backtrace /var/log/Xorg.0.log -- /usr/bin/abrt-dump-xorg -xD - - Ss 0:00 - If there's 2 or more '- -' after the process entry, it's multi=threaded. Note however that as far as the kernel is concerned, a single-threaded process is handled by the code as a multi-threaded that happens to have only one thread at the moment. In other words, thinking that single and multi threaded is different in some mystical way will probably end up causing trouble for you...
Hi, BTW, for a given thread group with a specified TGID, you can view all the threads PIDs in that thread group thus: pstree -p TGID and: pstree TGID will give one line; It visually merges identical branches by putting them in square brackets and prefixing them with the repetition count. Regards, Rami Rosen http://ramirose.wix.com/ramirosen On Tue, Apr 2, 2013 at 9:14 PM, <Valdis.Kletnieks@vt.edu> wrote:
On Tue, 02 Apr 2013 16:46:24 +0300, Kevin Wilson said:
Hi, Thanks a lot Vlad. This explains it. - Does anybody know of a ps command (or a filter to ps command) which will display only multithreaded processes (list processes by TGID) ? (I know now about the option of displaying cgroup.procs , but is something parallel can be done with ps ? )
Have you tried 'ps -m' and friends? Though it doesn't do exactly what you wanted and *only* display multithreaded, you need to do some post-processing:
$ ps max ... 928 ? - 0:00 /sbin/auditd -n - - S<sl 0:00 - - - S<sl 0:00 - 940 ? - 0:00 /sbin/audispd - - S<sl 0:00 - - - S<sl 0:00 - 951 ? - 0:00 /usr/sbin/abrtd -d -s - - Ss 0:00 - 960 ? - 0:00 /usr/bin/abrt-watch-log -F Backtrace /var/log/Xorg.0.log -- /usr/bin/abrt-dump-xorg -xD - - Ss 0:00 -
If there's 2 or more '- -' after the process entry, it's multi=threaded.
Note however that as far as the kernel is concerned, a single-threaded process is handled by the code as a multi-threaded that happens to have only one thread at the moment. In other words, thinking that single and multi threaded is different in some mystical way will probably end up causing trouble for you...
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participants (4)
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Kevin Wilson -
Rami Rosen -
Valdis.Kletnieks＠vt.edu -
Vlad Dogaru