lkml.org 
[lkml]   [2006]   [Oct]   [30]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
    /
    Date
    From
    SubjectRe: [PATCH] taskstats: fix sub-threads accounting

    Oleg Nesterov wrote:
    > If there are no listeners, taskstats_exit_send() just returns because
    > taskstats_exit_alloc() didn't allocate *tidstats. This is wrong, each
    > sub-thread should do fill_tgid_exit() on exit, otherwise its ->delays
    > is not recorded in ->signal->stats and lost.

    Good catch. Thanks for the detailed look at the delay accounting code.



    >
    > Q: We don't send TASKSTATS_TYPE_AGGR_TGID when single-threaded process
    > exits. Is it good? How can the listener figure out that it was actually
    > a process exit, not sub-thread?

    We had a detailed discussion on this on lkml earlier. The overhead of
    sending essentially the same data twice (once as AGGR_TGID and once as
    PID) was deemed too heavy esp. as the taskstats structure size grew.
    Also, single threaded exit is a common case.

    Using process events, its possible for user space to distinguish single
    threaded process exits.

    >
    > Signed-off-by: Oleg Nesterov <oleg@tv-sign.ru>

    Acked-by: Shailabh Nagar <nagar@watson.ibm.com>

    >
    > --- STATS/kernel/taskstats.c~2_send 2006-10-30 23:47:46.000000000 +0300
    > +++ STATS/kernel/taskstats.c 2006-10-31 00:14:42.000000000 +0300
    > @@ -446,10 +446,9 @@ void taskstats_exit_send(struct task_str
    > int is_thread_group;
    > struct nlattr *na;
    >
    > - if (!family_registered || !tidstats)
    > + if (!family_registered)
    > return;
    >
    > - rc = 0;
    > /*
    > * Size includes space for nested attributes
    > */
    > @@ -457,8 +456,15 @@ void taskstats_exit_send(struct task_str
    > nla_total_size(sizeof(struct taskstats)) + nla_total_size(0);
    >
    > is_thread_group = (tsk->signal->stats != NULL);
    > - if (is_thread_group)
    > - size = 2 * size; /* PID + STATS + TGID + STATS */
    > + if (is_thread_group) {
    > + /* PID + STATS + TGID + STATS */
    > + size = 2 * size;
    > + /* fill the tsk->signal->stats structure */
    > + fill_tgid_exit(tsk);
    > + }
    > +
    > + if (!tidstats)
    > + return;
    >
    > rc = prepare_reply(NULL, TASKSTATS_CMD_NEW, &rep_skb, &reply, size);
    > if (rc < 0)
    > @@ -478,11 +484,8 @@ void taskstats_exit_send(struct task_str
    > goto send;
    >
    > /*
    > - * tsk has/had a thread group so fill the tsk->signal->stats structure
    > * Doesn't matter if tsk is the leader or the last group member leaving
    > */
    > -
    > - fill_tgid_exit(tsk);
    > if (!group_dead)
    > goto send;
    >
    >

    -
    To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
    the body of a message to majordomo@vger.kernel.org
    More majordomo info at http://vger.kernel.org/majordomo-info.html
    Please read the FAQ at http://www.tux.org/lkml/

    \
     
     \ /
      Last update: 2006-10-31 04:05    [W:0.035 / U:29.996 seconds]
    ©2003-2016 Jasper Spaans. hosted at Digital OceanAdvertise on this site