Re: perf: bisected sampling bug in Linux 4.11-rc1

From	Vince Weaver <vincent.weaver@maine.edu>
Newsgroups	linux.kernel
Subject	Re: perf: bisected sampling bug in Linux 4.11-rc1
Date	2017-07-16 05:10 +0200
Message-ID	<u3I6t-1BN-1@gated-at.bofh.it> (permalink)
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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

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perf: bisected sampling bug in Linux 4.11-rc1 Vince Weaver <vincent.weaver@maine.edu> - 2017-07-14 20:10 +0200
  Re: perf: bisected sampling bug in Linux 4.11-rc1 Vince Weaver <vincent.weaver@maine.edu> - 2017-07-14 20:30 +0200
  Re: perf: bisected sampling bug in Linux 4.11-rc1 Alexander Shishkin <alexander.shishkin@linux.intel.com> - 2017-07-14 22:10 +0200
    Re: perf: bisected sampling bug in Linux 4.11-rc1 Vince Weaver <vincent.weaver@maine.edu> - 2017-07-14 22:20 +0200
  Re: perf: bisected sampling bug in Linux 4.11-rc1 Ingo Molnar <mingo@kernel.org> - 2017-07-15 13:10 +0200
    Re: perf: bisected sampling bug in Linux 4.11-rc1 Vince Weaver <vincent.weaver@maine.edu> - 2017-07-15 16:40 +0200
      Re: perf: bisected sampling bug in Linux 4.11-rc1 Vince Weaver <vincent.weaver@maine.edu> - 2017-07-16 05:10 +0200

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