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    SubjectRe: [patch v2 4/4] taskstats: Export "cdata_wait" CPU times with taskstats
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    Hello Balbir,

    On Fri, 2010-12-03 at 13:03 +0530, Balbir Singh wrote:
    > * Oleg Nesterov <oleg@redhat.com> [2010-12-01 19:51:28]:
    >
    > > On 11/29, Michael Holzheu wrote:
    [snip]
    > > Say, taskstats_exit()->fill_stats()->bacct_add_tsk(). Every thread
    > > does this, including the group_leader. But, it is possible that
    > > group_leader exits first, before other threads. IOW, what
    > > stats->ac_cXtime actually mean?
    > >
    >
    > stats->ac_* time was designed only for tgid's to begin with,

    You mean for tids (threads/tasks), no? stats->ac_* time is only reported
    for threads in bacct_add_tsk() and not for tgids.

    > so I am
    > not sure if ac_cXtime makes sense for threads

    I would suggest to do it the same way as /proc/<tgid>/tasks/<tid>/stat.
    It reports the (same) cumulative time for each thread. See
    do_task_stat() in fs/proc/array.c. So IMHO also for taskstats it makes
    sense to include the cXtime for all threads and not only for the thread
    group leader.

    Also I would include tgid in taskstats so that userspace can group the
    tasks into thread groups.

    I am not sure regarding the aggregation for tgids in
    TASKSTATS_CMD_ATTR_TGID and exit events with group_dead=1. Currently
    only the delay accounting numbers are aggregated. If we would do it
    like /proc/<tgid>/stat (do_task_stat() with whole=1) we also could
    aggregate also the other values e.g. the CPU time.

    I think the following tgid data would make sense to be returned for
    TASKSTATS_CMD_ATTR_TGID and exit events with group_dead=1:

    bacct_add_tsk():
    ----------------
    ac_pid thread group leader (tsk->tgid)
    ac_etime thread group leader
    ac_btime thread group leader
    ac_nice thread group leader
    ac_sched thread group leader
    ac_uid thread group leader
    ac_gid thread group leader
    ac_ppid thread group leader
    ac_comm thread group leader
    ac_exit_code thread group leader
    ac_flags thread group leader
    ac_utimescaled ??
    ac_stimescaled ??
    ac_utime sum for all live threads + cdata_threads
    ac_stime sum for all live threads + cdata_threads
    ac_minflt sum for all live threads + cdata_threads
    ac_majflt sum for all live threads + cdata_threads

    new:
    ac_cutime cdata_wait
    ac_cstime cdata_wait
    ac_tgid thread group leader

    xacct_add_tsk():
    ----------------
    coremem ?
    virtmem ?
    hiwater_rss thread group leader
    hiwater_vm thread group leader
    read_char sum for all live threads + tsk->signal.ioac
    write_char sum for all live threads + tsk->signal.ioac
    read_syscalls sum for all live threads + tsk->signal.ioac
    write_syscalls sum for all live threads + tsk->signal.ioac
    read_bytes sum for all live threads + tsk->signal.ioac
    write bytes sum for all live threads + tsk->signal.ioac
    cancelled_write_bytes sum for all live threads + tsk->signal.ioac

    If we leave everything as it currently is for tgid accounting, we
    probably should also not include the cXtime for tgids and just include
    the data for threads (TASKSTATS_CMD_ATTR_PID and task exit events).

    What do you think?

    Michael






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