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    SubjectRe: [Patch][RFC] Disabling per-tgid stats on task exit in taskstats
    On Fri, 09 Jun 2006 16:21:46 +0530
    Balbir Singh <balbir@in.ibm.com> wrote:

    > Andrew Morton wrote:
    > > On Fri, 09 Jun 2006 03:41:04 -0400
    > > Shailabh Nagar <nagar@watson.ibm.com> wrote:
    > >
    > >
    > >>Hence, this patch introduces a configuration parameter
    > >> /sys/kernel/taskstats_tgid_exit
    > >>through which a privileged user can turn on/off sending of per-tgid stats on
    > >>task exit.
    > >
    > >
    > > That seems a bit clumsy. What happens if one consumer wants the per-tgid
    > > stats and another does not?
    >
    > For all subsystems that re-use the taskstats structure from the exit path,
    > we have the issue that you mentioned. Thats because several statistics co-exist
    > in the same structure. These subsystems can keep their tgid-stats empty by not
    > filling up anything in fill_tgid() or using this patch to selectively enable/disable
    > tgid stats.
    >
    > For other subsystems, they could pass tgidstats as NULL to taskstats_exit_send().
    >

    I don't understand. If a subsystem exists then it fills in its slots in
    the taskstats structure, doesn't it?

    No other subsystem needs a global knob, does it?

    You see the problem - if one userspace package wants the tgid-stats and
    another concurrently-running one does now, what do we do? Just leave it
    enabled and run a bit slower?

    If so, how much slower? Your changelog says some potential users don't
    need the tgid-stats, but so what? I assume this patch is a performance
    thing? If so, has it been quantified?

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