linux-kernel - Re: [RFC] perf tool improvement requests

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Message-ID: <20180904071049.GY24124@hirez.programming.kicks-ass.net>
Date:   Tue, 4 Sep 2018 09:10:49 +0200
From:   Peter Zijlstra <peterz@...radead.org>
To:     Stephane Eranian <eranian@...gle.com>
Cc:     Arnaldo Carvalho de Melo <acme@...nel.org>,
        Jiri Olsa <jolsa@...hat.com>, Jiri Olsa <jolsa@...nel.org>,
        LKML <linux-kernel@...r.kernel.org>,
        Namhyung Kim <namhyung@...nel.org>
Subject: Re: [RFC] perf tool improvement requests

On Mon, Sep 03, 2018 at 07:45:48PM -0700, Stephane Eranian wrote:
> Hi Arnaldo, Jiri,
> 
> A few weeks ago, you had asked if I had more requests for the perf tool.

I have one long standing one; that is IP based data structure
annotation.

When we get an exact IP (using PEBS) and were sampling a data related
event (say L1 misses), we can get the data type from the instruction
itself; that is, through DWARF. We _know_ what type (structure::member)
is read/written to.

I would love to get that in a pahole style output.

Better yet, when you measure both hits and misses, you can get a
structure usage overview, and see what lines are used lots and what
members inside that line are rarely used. Ideal information for data
structure layout optimization.

1000x more useful than that c2c crap.

Can we please get that?