linux-kernel - Re: [LKP] [lkp] [xfs] 68a9f5e700: aim7.jobs-per-min -13.6% regression

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Date:	Mon, 15 Aug 2016 07:03:00 +0200
From:	Ingo Molnar <mingo@...nel.org>
To:	Linus Torvalds <torvalds@...ux-foundation.org>
Cc:	Dave Chinner <david@...morbit.com>, Tejun Heo <tj@...nel.org>,
	Wu Fengguang <fengguang.wu@...el.com>,
	"Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>,
	Christoph Hellwig <hch@....de>,
	"Huang, Ying" <ying.huang@...el.com>,
	LKML <linux-kernel@...r.kernel.org>,
	Bob Peterson <rpeterso@...hat.com>, LKP <lkp@...org>,
	Arnaldo Carvalho de Melo <acme@...radead.org>,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>
Subject: Re: [LKP] [lkp] [xfs] 68a9f5e700: aim7.jobs-per-min -13.6% regression


* Linus Torvalds <torvalds@...ux-foundation.org> wrote:

> Make sure you actually use "perf record -e cycles:pp" or something
> that uses PEBS to get real profiles using CPU performance counters.

Btw., 'perf record -e cycles:pp' is the default now for modern versions
of perf tooling (on most x86 systems) - if you do 'perf record' it will
just use the most precise profiling mode available on that particular
CPU model.

If unsure you can check the event that was used, via:

  triton:~> perf report --stdio 2>&1 | grep '# Samples'
  # Samples: 27K of event 'cycles:pp'

Thanks,

	Ingo