From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751300AbaJCHeY (ORCPT ); Fri, 3 Oct 2014 03:34:24 -0400 Received: from mx1.redhat.com ([209.132.183.28]:7396 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750731AbaJCHeW (ORCPT ); Fri, 3 Oct 2014 03:34:22 -0400 Date: Fri, 3 Oct 2014 09:33:54 +0200 From: Jiri Olsa To: Alexander Yarygin Cc: linux-kernel@vger.kernel.org, Arnaldo Carvalho de Melo , Christian Borntraeger , David Ahern , Frederic Weisbecker , Ingo Molnar , Mike Galbraith , Namhyung Kim , Paul Mackerras , Peter Zijlstra , Stephane Eranian Subject: Re: [PATCH 1/2] perf tools: Add option to copy events when queueing Message-ID: <20141003073354.GA19087@krava.brq.redhat.com> References: <1412267936-19827-1-git-send-email-yarygin@linux.vnet.ibm.com> <1412267936-19827-2-git-send-email-yarygin@linux.vnet.ibm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1412267936-19827-2-git-send-email-yarygin@linux.vnet.ibm.com> User-Agent: Mutt/1.5.23 (2014-03-12) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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 > > Signed-off-by: Alexander Yarygin > Cc: Arnaldo Carvalho de Melo > Cc: Christian Borntraeger > Cc: Frederic Weisbecker > Cc: Ingo Molnar > Cc: Jiri Olsa > Cc: Mike Galbraith > Cc: Namhyung Kim > Cc: Peter Zijlstra > Cc: Stephane Eranian > --- > 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 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