Messages in this thread | | | Date | Fri, 3 Oct 2014 09:33:54 +0200 | From | Jiri Olsa <> | Subject | Re: [PATCH 1/2] perf tools: Add option to copy events when queueing |
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On Thu, Oct 02, 2014 at 08:38:55PM +0400, Alexander Yarygin wrote: > When processing events the session code has an ordered samples queue which is > used to time-sort events coming in across multiple mmaps. At a later point in > time samples on the queue are flushed up to some timestamp at which point the > event is actually processed. > > When analyzing events live (ie., record/analysis path in the same command) > there is a race that leads to corrupted events and parse errors which cause > perf to terminate. The problem is that when the event is placed in the ordered > samples queue it is only a reference to the event which is really sitting in > the mmap buffer. Even though the event is queued for later processing the mmap > tail pointer is updated which indicates to the kernel that the event has been > processed. The race is flushing the event from the queue before it gets > overwritten by some other event. For commands trying to process events live > (versus just writing to a file) and processing a high rate of events this leads > to parse failures and perf terminates. > > Examples hitting this problem are 'perf kvm stat live', especially with nested > VMs which generate 100,000+ traces per second, and a command processing > scheduling events with a high rate of context switching -- e.g., running > 'perf bench sched pipe'. > > This patch offers live commands an option to copy the event when it is placed in > the ordered samples queue. > > Based on a patch from David Ahern <dsahern@gmail.com> > > Signed-off-by: Alexander Yarygin <yarygin@linux.vnet.ibm.com> > Cc: Arnaldo Carvalho de Melo <acme@kernel.org> > Cc: Christian Borntraeger <borntraeger@de.ibm.com> > Cc: Frederic Weisbecker <fweisbec@gmail.com> > Cc: Ingo Molnar <mingo@kernel.org> > Cc: Jiri Olsa <jolsa@redhat.com> > Cc: Mike Galbraith <efault@gmx.de> > Cc: Namhyung Kim <namhyung.kim@lge.com> > Cc: Peter Zijlstra <a.p.zijlstra@chello.nl> > Cc: Stephane Eranian <eranian@google.com> > --- > tools/perf/util/ordered-events.c | 51 ++++++++++++++++++++++++++++++++++++---- > tools/perf/util/ordered-events.h | 10 +++++++- > tools/perf/util/session.c | 5 ++-- > 3 files changed, 58 insertions(+), 8 deletions(-)
apart from extra whitespaces (below): Acked-by: Jiri Olsa <jolsa@kernel.org>
thanks, jirka
> > diff --git a/tools/perf/util/ordered-events.c b/tools/perf/util/ordered-events.c > index 706ce1a..06d53ee 100644 > --- a/tools/perf/util/ordered-events.c > +++ b/tools/perf/util/ordered-events.c
SNIP
> + } > > pr("alloc size %" PRIu64 "B (+%zu), max %" PRIu64 "B\n", > oe->cur_alloc_size, size, oe->max_alloc_size); > @@ -90,15 +127,19 @@ static struct ordered_event *alloc_event(struct ordered_events *oe) > pr("allocation limit reached %" PRIu64 "B\n", oe->max_alloc_size); > } > > + new->event = new_event; > + > return new;
^^^ here
> } > > struct ordered_event * > -ordered_events__new(struct ordered_events *oe, u64 timestamp) > +ordered_events__new(struct ordered_events *oe, u64 timestamp, > + union perf_event *event) > { > struct ordered_event *new; > > - new = alloc_event(oe); > + new = alloc_event(oe, event); > + > if (new) {
^^^ and here
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