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    SubjectRe: [Patch][RFC] Disabling per-tgid stats on task exit in taskstats
    Andrew Morton wrote:
    > On Thu, 29 Jun 2006 09:44:08 -0700
    > Paul Jackson <pj@sgi.com> wrote:
    >
    >
    >>>You're probably correct on that model. However, it all depends on the actual
    >>>workload. Are people who actually have large-CPU (>256) systems actually
    >>>running fork()-heavy things like webservers on them, or are they running things
    >>>like database servers and computations, which tend to have persistent
    >>>processes?
    >>
    >>It may well be mostly as you say - the large-CPU systems not running
    >>the fork() heavy jobs.
    >>
    >>Sooner or later, someone will want to run a fork()-heavy job on a
    >>large-CPU system. On a 1024 CPU system, it would apparently take
    >>just 14 exits/sec/CPU to hit this bottleneck, if Jay's number of
    >>14000 applied.
    >>
    >>Chris Sturdivant's reply is reasonable -- we'll hit it sooner or later,
    >>and deal with it then.
    >>
    >
    >
    > I agree, and I'm viewing this as blocking the taskstats merge. Because if
    > this _is_ a problem then it's a big one because fixing it will be
    > intrusive, and might well involve userspace-visible changes.
    >
    > The only ways I can see of fixing the problem generally are to either
    >
    > a) throw more CPU(s) at stats collection: allow userspace to register for
    > "stats generated by CPU N", then run a stats collection daemon on each
    > CPU or

    Clearly this approach (or the per-cpuset as Paul suggested) can solve
    large-CPU system issues. As technology advances, this _WILL_ become a
    problem sooner or later.

    However, taskstats header carries a version number. Would a change like
    this too intrusive to add to a later version?

    Regards,
    - jay


    >
    > b) make the kernel recognise when it's getting overloaded and switch to
    > some degraded mode where it stops trying to send all the data to
    > userspace - just send a summary, or a "we goofed" message or something.

    -
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