linux-kernel - Re: [PATCH 4/4] perf script: Add script to collect and display IBS samples

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Date:	Fri, 23 Dec 2011 15:14:58 +0100
From:	Peter Zijlstra <peterz@...radead.org>
To:	Ingo Molnar <mingo@...e.hu>
Cc:	Robert Richter <robert.richter@....com>,
	Arnaldo Carvalho de Melo <acme@...hat.com>,
	Stephane Eranian <eranian@...gle.com>,
	LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 4/4] perf script: Add script to collect and display IBS
 samples

On Fri, 2011-12-23 at 14:53 +0100, Ingo Molnar wrote:
> * Robert Richter <robert.richter@....com> wrote:
> 
> > > Also, could you quote example output of "perf script report 
> > > ibs"?
> > 
> > IBS_FETCH sample on cpu6	IBS0: 0x00170003186a186a IBS1: 0x0000000000444780 IBS2:0x000000041af26780
> > IBS_FETCH sample on cpu6	IBS0: 0x00170003186a186a IBS1: 0x00007f5efb44e3b2 IBS2:0x000000042fcff3b2
> > IBS_FETCH sample on cpu6	IBS0: 0x01370003186a186a IBS1: 0xffffffff81065273 IBS2:0x0000000001065273
> > IBS_FETCH sample on cpu6	IBS0: 0x01370003186a186a IBS1: 0xffffffff811a6320 IBS2:0x00000000011a6320
> > IBS_FETCH sample on cpu6	IBS0: 0x01370003186a186a IBS1: 0xffffffff81065255 IBS2:0x0000000001065255
> > IBS_FETCH sample on cpu7	IBS0: 0x00170004186a186a IBS1: 0x00007fbf0c687ca0 IBS2:0x000000041d345ca0
> > IBS_FETCH sample on cpu7	IBS0: 0x00170003186a186a IBS1: 0x000000000043bb80 IBS2:0x000000041c351b80
> > IBS_FETCH sample on cpu7	IBS0: 0x01370003186a186a IBS1: 0xffffffff813d5790 IBS2:0x00000000013d5790
> > IBS_FETCH sample on cpu7	IBS0: 0x00030001186a186a IBS1: 0xffffffff8102bd00 IBS2:0x00000000013d5d00
> 
> That does not look very usable to users. So why should we merge 
> this new ABI in its incomplete form with no complete usecase? 
> Being usable is clearly not outside the scope of a new feature 
> ...
> 
> Integrating it into perf report should not be *that* hard, 
> you've done most of the hard work already. But without that step 
> we just don't know how complete and usable the whole thing is.

perf annotate like output might make more sense for IBS, maybe not
decode all the information that's in there, but at least a number of the
most useful measurements for each type and present multiple columns in
front of the instructions.

Ingo, the trouble with IBS is that it doesn't measure something, its a
measure everything together like thing, so what particular part of this
massive bulk data do you use to create your histograms?
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