linux-kernel - Re: [PATCH 16/29] perf, tools: Add support for weight v7

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Message-ID: <CABPqkBQvh5R32mxvLsaN2+YmBhxcoRmUYUZeQju4kBDnHB4s5A@mail.gmail.com>
Date:	Wed, 23 Jan 2013 18:25:04 +0100
From:	Stephane Eranian <eranian@...gle.com>
To:	Andi Kleen <andi@...stfloor.org>
Cc:	"mingo@...e.hu" <mingo@...e.hu>,
	LKML <linux-kernel@...r.kernel.org>,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Arnaldo Carvalho de Melo <acme@...hat.com>,
	Jiri Olsa <jolsa@...hat.com>,
	Namhyung Kim <namhyung@...nel.org>,
	Andi Kleen <ak@...ux.intel.com>
Subject: Re: [PATCH 16/29] perf, tools: Add support for weight v7

On Wed, Jan 23, 2013 at 6:13 PM, Andi Kleen <andi@...stfloor.org> wrote:
>> For PEBS-LL and possibly other special cases, it is important to remember
>> that perf report always end up sorting by period (hist_collapse_resort). But
>> for PEBS-LL we want to sort on nr_events * weight. Thus, with your patch,
>> the only way, I found, to achieve this is by passing:
>>
>>        add_hist_entry(self, &entry, al, weight, weight);
>
> Seems like a hack. IMHO it should always sort by all the keys
> i specified with --sort in exactly that order I specified
>
Well, it does except for the "implicit" column which uses period, see
hists__collapse_resort().
And that function is hardcoded to only look at period.

As for the hack, I did not put in in my hist__add_mem_entry() but
rather in the caller.
For PEBS-LL, the period is not important. I think it counts the number
of loads/stores
and not just the qualifying ones. For loads, that means it counts all
loads and not just
the ones above the threshold, but I may be wrong.

> I had a similar thing in a really old version of my patches,
> but I gave it up because it was too unintuitive.
>
Well, but then it does not present a sensible view of the samples when weight is
more important than period.

> -Andi
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