linux-kernel - Re: [patch] Performance Counters for Linux, v4

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Message-ID: <18758.18075.30744.666904@cargo.ozlabs.ibm.com>
Date:	Mon, 15 Dec 2008 22:59:23 +1100
From:	Paul Mackerras <paulus@...ba.org>
To:	Ingo Molnar <mingo@...e.hu>
Cc:	linux-kernel@...r.kernel.org, Thomas Gleixner <tglx@...utronix.de>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Stephane Eranian <eranian@...glemail.com>,
	Eric Dumazet <dada1@...mosbay.com>,
	Robert Richter <robert.richter@....com>,
	Arjan van de Ven <arjan@...radead.org>,
	Peter Anvin <hpa@...or.com>,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	"David S. Miller" <davem@...emloft.net>,
	perfctr-devel@...ts.sourceforge.net
Subject: Re: [patch] Performance Counters for Linux, v4

Ingo Molnar writes:

> For example, a full kernel build's statistics on a 16-way x86 box are:
> 
>   $ timec -e -5,-4,-3,1,2,3,5 make -j32 bzImage
> 
>   Performance counter stats for 'make':
> 
>          142420.882  task clock ticks     (millisecs)
> 
>             9951033  pagefaults           (events)
>              302628  context switches     (events)
>               57810  CPU migrations       (events)
>        208439082509  instructions         (events)
>           657918810  cache references     (events)
>           120243697  cache misses         (events)
>          3134162468  branch misses        (events)

Does this machine have sufficient hardware counters to count those
four hardware events at the same time?  Or were those counters
timeshared onto 1 or 2 hardware counters?  If it's the latter, are
those counts from half or a quarter of the total execution?

Paul.
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