Re: [patch] Performance Counters for Linux, v4

From: Paul Mackerras <paulus@samba.org>
To: Ingo Molnar <mingo@elte.hu>
Cc: linux-kernel@vger.kernel.org,
	Thomas Gleixner <tglx@linutronix.de>,
	Andrew Morton <akpm@linux-foundation.org>,
	Stephane Eranian <eranian@googlemail.com>,
	Eric Dumazet <dada1@cosmosbay.com>,
	Robert Richter <robert.richter@amd.com>,
	Arjan van de Ven <arjan@infradead.org>,
	Peter Anvin <hpa@zytor.com>,
	Peter Zijlstra <a.p.zijlstra@chello.nl>,
	"David S. Miller" <davem@davemloft.net>,
	perfctr-devel@lists.sourceforge.net
Subject: Re: [patch] Performance Counters for Linux, v4
Date: Mon, 15 Dec 2008 22:59:23 +1100	[thread overview]
Message-ID: <18758.18075.30744.666904@cargo.ozlabs.ibm.com> (raw)
In-Reply-To: <20081214212829.GA9435@elte.hu>

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.