linux-kernel - Re: [generalized cache events] Re: [PATCH 1/1] perf tools: Add missing user space support for config1/config2

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Date:	Fri, 22 Apr 2011 22:32:22 +0200
From:	Ingo Molnar <mingo@...e.hu>
To:	arun@...rma-home.net
Cc:	Stephane Eranian <eranian@...gle.com>,
	Arnaldo Carvalho de Melo <acme@...radead.org>,
	linux-kernel@...r.kernel.org, Andi Kleen <ak@...ux.intel.com>,
	Peter Zijlstra <peterz@...radead.org>,
	Lin Ming <ming.m.lin@...el.com>,
	Arnaldo Carvalho de Melo <acme@...hat.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>, eranian@...il.com,
	Arun Sharma <asharma@...com>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Andrew Morton <akpm@...ux-foundation.org>
Subject: Re: [generalized cache events] Re: [PATCH 1/1] perf tools: Add
 missing user space support for config1/config2


* Ingo Molnar <mingo@...e.hu> wrote:

> * arun@...rma-home.net <arun@...rma-home.net> wrote:
> 
> > On Fri, Apr 22, 2011 at 12:52:11PM +0200, Ingo Molnar wrote:
> > > 
> > > Using the generalized cache events i can run:
> > > 
> > >  $ perf stat --repeat 10 -e cycles:u -e instructions:u -e l1-dcache-loads:u -e l1-dcache-load-misses:u ./array
> > > 
> > >  Performance counter stats for './array' (10 runs):
> > > 
> > >          6,719,130 cycles:u                   ( +-   0.662% )
> > >          5,084,792 instructions:u           #      0.757 IPC     ( +-   0.000% )
> > >          1,037,032 l1-dcache-loads:u          ( +-   0.009% )
> > >          1,003,604 l1-dcache-load-misses:u    ( +-   0.003% )
> > > 
> > >         0.003802098  seconds time elapsed   ( +-  13.395% )
> > > 
> > > I consider that this is 'bad', because for almost every dcache-load there's a 
> > > dcache-miss - a 99% L1 cache miss rate!
> > 
> > One could argue that all you need is cycles and instructions. [...]
> 
> Yes, and note that with instructions events we even have skid-less PEBS 
> profiling so seeing the precise .
                                  - location of instructions is possible.

[ An email gremlin ate that part of the sentence. ]

Thanks,

	Ingo
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