From: Vince Weaver <vincent.weaver@maine.edu>
To: Ingo Molnar <mingo@kernel.org>
Cc: linux-kernel@vger.kernel.org,
Alexander Shishkin <alexander.shishkin@linux.intel.com>,
Peter Zijlstra <peterz@infradead.org>,
Stephane Eranian <eranian@gmail.com>,
Jiri Olsa <jolsa@redhat.com>,
Arnaldo Carvalho de Melo <acme@infradead.org>,
Thomas Gleixner <tglx@linutronix.de>
Subject: Re: perf: bisected sampling bug in Linux 4.11-rc1
Date: Sat, 15 Jul 2017 23:03:06 -0400 (EDT) [thread overview]
Message-ID: <alpine.DEB.2.20.1707152259180.30679@macbook-air> (raw)
In-Reply-To: <alpine.DEB.2.20.1707151033130.29924@macbook-air>
On Sat, 15 Jul 2017, Vince Weaver wrote:
> Although there is a separate issue also introduced in 4.11-rc1 that still
> fails a different testcase. I'm in the middle of bisecting that one and
> probably won't have the result of the bisect until Monday.
I went and bisected the other issue anyway. It wasn't in 4.11-rc1, but in
4.12-rc4. Yes, I have a test that triggered the
c1582c231ea041 perf/core: Drop kernel samples even though :u is specified
issue.
The test was actually losing 7% of its samples, so not just a single
sample here or there. The test had two events sampling, one at 100k and
one at 200k so I guess every other sample would have two samples
immediately back-to-back which must make it more likely to stray into the
kernel.
Vince
next prev parent reply other threads:[~2017-07-16 3:03 UTC|newest]
Thread overview: 12+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-07-14 18:05 Vince Weaver
2017-07-14 18:25 ` Vince Weaver
2017-07-14 20:07 ` Alexander Shishkin
2017-07-14 20:14 ` Vince Weaver
2017-07-15 11:00 ` Ingo Molnar
2017-07-15 14:37 ` Vince Weaver
2017-07-16 3:03 ` Vince Weaver [this message]
2017-07-18 10:39 ` [tip:perf/urgent] Revert "perf/core: Optimize event rescheduling on active contexts" tip-bot for Ingo Molnar
2017-07-18 11:08 ` perf: bisected sampling bug in Linux 4.11-rc1 Alexander Shishkin
2017-07-18 12:13 ` Ingo Molnar
2017-07-20 3:30 ` Vince Weaver
2017-07-20 8:34 ` [tip:perf/urgent] perf/core: Fix scheduling regression of pinned groups tip-bot for Alexander Shishkin
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