linux-kernel - Re: [patch] x86, perf_counter, bts: add bts to perf

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Date:	Fri, 7 Aug 2009 13:26:34 +0200
From:	Ingo Molnar <mingo@...e.hu>
To:	"Metzger, Markus T" <markus.t.metzger@...el.com>
Cc:	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	"tglx@...utronix.de" <tglx@...utronix.de>,
	"hpa@...or.com" <hpa@...or.com>,
	"markus.t.metzger@...il.com" <markus.t.metzger@...il.com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [patch] x86, perf_counter, bts: add bts to perf_counter


btw., the number of samples seems to be varying too widely:

titan:~> for ((i=0;i<10;i++)); do perf record -f -e branches:u -c 1 true 2>/dev/null; perf report | head -1; done
# Samples: 28784
# Samples: 24063
# Samples: 22788
# Samples: 30449
# Samples: 15335
# Samples: 30557
# Samples: 24010
# Samples: 23866
# Samples: 24877
# Samples: 24330

compared to the branch-stat itself:

titan:~> perf stat -v --repeat 10 -e branches:u true
[ perf stat: executing run #1 ... ]
[ perf stat: executing run #2 ... ]
[ perf stat: executing run #3 ... ]
[ perf stat: executing run #4 ... ]
[ perf stat: executing run #5 ... ]
[ perf stat: executing run #6 ... ]
[ perf stat: executing run #7 ... ]
[ perf stat: executing run #8 ... ]
[ perf stat: executing run #9 ... ]
[ perf stat: executing run #10 ... ]

 Performance counter stats for 'true' (10 runs):

          23851  branches                   ( +-   0.000% )

    0.000639653  seconds time elapsed   ( +-   2.474% )

do we lose records in the recording?

	Ingo
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