From: Vince Weaver <vincent.weaver@maine.edu>
To: linux-kernel@vger.kernel.org
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>,
Ingo Molnar <mingo@kernel.org>,
Peter Zijlstra <peterz@infradead.org>,
Stephane Eranian <eranian@gmail.com>
Subject: Re: perf: bisected sampling bug in Linux 4.11-rc1
Date: Fri, 14 Jul 2017 14:25:56 -0400 (EDT) [thread overview]
Message-ID: <alpine.DEB.2.20.1707141425030.28006@macbook-air> (raw)
In-Reply-To: <alpine.DEB.2.20.1707141332050.27846@macbook-air>
On Fri, 14 Jul 2017, Vince Weaver wrote:
> On a good kernel you get the following:
> Event perf::instructions with period 1000000
> Event perf::instructions with period 2000000
> fd 3 overflows: 946 (perf::instructions/1000000)
> fd 4 overflows: 473 (perf::instructions/2000000)
> Ending counts:
> Count 0: 946379875
> Count 1: 946365218
>
> With the broken kernels you get:
> Event perf::instructions with period 1000000
> Event perf::instructions with period 2000000
> fd 3 overflows: 938 (perf::instructions/1000000)
> fd 4 overflows: 318 (perf::instructions/2000000)
> Ending counts:
> Count 0: 946373080
> Count 1: 653373058
additional relevant detail:
in the failing case, the group leader of the event set has
.pinned=1
If I change that to .pinned=0 then the test passes.
Vince
next prev parent reply other threads:[~2017-07-14 18:26 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 [this message]
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
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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