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 <[email protected]> > > Signed-off-by: Alexander Yarygin <[email protected]> > Cc: Arnaldo Carvalho de Melo <[email protected]> > Cc: Christian Borntraeger <[email protected]> > Cc: Frederic Weisbecker <[email protected]> > Cc: Ingo Molnar <[email protected]> > Cc: Jiri Olsa <[email protected]> > Cc: Mike Galbraith <[email protected]> > Cc: Namhyung Kim <[email protected]> > Cc: Peter Zijlstra <[email protected]> > Cc: Stephane Eranian <[email protected]> > --- > 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 <[email protected]> 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 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
