linux-kernel - Re: [PATCH 2/6 -tip] perf stat: treat same behaviour for all CYCLES and CLOCKS

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Date:	Fri, 3 Jul 2009 18:18:04 +1000
From:	Paul Mackerras <paulus@...ba.org>
To:	Ingo Molnar <mingo@...e.hu>
Cc:	Jaswinder Singh Rajput <jaswinder@...nel.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	Peter Zijlstra <peterz@...radead.org>,
	x86 maintainers <x86@...nel.org>,
	LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 2/6 -tip] perf stat: treat same behaviour for all
	CYCLES and CLOCKS

Ingo Molnar writes:

> Other 'compound' events might be possible too: for example a new 
> cache-hits field could be is cache-refs minus cache-misses.

Hmmm, on the MPC7450 family there are events for cache-hits and
cache-misses, so there it would be nice to be able to ask for
cache-refs and have it compute cache-hits plus cache-misses.

> I.e. the simplest model for 'compound' events would be:
> 
>   X = A / B
>   X = A - B
>   X = A + B
> 
> We could list them in the event table, with a flag that specifies 
> which arithmetic operation connects two 'atomic' counters.
> 
> Then the adding of a new compound event would only be the matter of 
> adding one more line to the event table.

Sounds nice.  If we do this we should ensure that the two events
get put into one group if possible.

Paul.
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