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    SubjectRe: [PATCH] perf tools: Do not fail on processing out of order event

    * Arnaldo Carvalho de Melo <acme@redhat.com> wrote:

    > Em Wed, Nov 26, 2014 at 04:39:31PM +0100, Jiri Olsa escreveu:
    > > Linus reported perf report command being interrupted due to
    > > processing of 'out of order' event, with following error:
    > >
    > > Timestamp below last timeslice flush
    > > 0x5733a8 [0x28]: failed to process type: 3
    > >
    > > I could reproduce the issue and in my case it was caused by one
    > > CPU (mmap) being behind during record and userspace mmap reader
    > > seeing the data after other CPUs data were already stored.
    > >
    > > It'd be nice to find the source of this hiccup, meanwhile I'm
    > > submitting change that does not kill the processing, but only
    > > tracks the number of out of order events and warn user.
    >
    > Works, for me, thanks for the fast response!

    Thanks Jiri!

    > > --- a/tools/perf/util/session.c
    > > +++ b/tools/perf/util/session.c
    > > @@ -533,15 +533,11 @@ int perf_session_queue_event(struct perf_session *s, union perf_event *event,
    > > return -ETIME;
    > >
    > > if (timestamp < oe->last_flush) {
    > > - WARN_ONCE(1, "Timestamp below last timeslice flush\n");
    > > -
    > > - pr_oe_time(timestamp, "out of order event");
    > > + pr_oe_time(timestamp, "out of order event\n");
    > > pr_oe_time(oe->last_flush, "last flush, last_flush_type %d\n",
    > > oe->last_flush_type);
    > >
    > > - /* We could get out of order messages after forced flush. */
    > > - if (oe->last_flush_type != OE_FLUSH__HALF)
    > > - return -EINVAL;
    > > + s->stats.nr_unordered_events++;

    Btw., in the forced flush case we'll get out of order events that
    are 'expected'. Shouldn't we count them separately and not warn
    about them, or so?

    > > + if (session->stats.nr_unordered_events != 0) {
    > > + ui__warning("%u out of order events recorded.\n",
    > > + session->stats.nr_unordered_events);
    > > + }

    Nit: I'd suggest keeping the message printout on a single line:

    if (session->stats.nr_unordered_events != 0) {
    ui__warning("%u out of order events recorded.\n", session->stats.nr_unordered_events);

    as IMHO the cure for this col80 linebreak checkpatch warning is
    worse than the disease! :-)

    Barring those details:

    Acked-by: Ingo Molnar <mingo@kernel.org>

    Arnaldo, I suppose the fix will go upstream via your tree, as a
    pull request for v3.18 fixes?

    Thanks,

    Ingo


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