linux-kernel - Re: [PATCH -tip v3 3/6] perf branch trace: print pid and command

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Message-ID: <4D96072E.4060902@gmail.com>
Date:	Fri, 01 Apr 2011 11:11:10 -0600
From:	David Ahern <dsahern@...il.com>
To:	Frederic Weisbecker <fweisbec@...il.com>
CC:	Akihiro Nagai <akihiro.nagai.hw@...achi.com>,
	Arnaldo Carvalho de Melo <acme@...radead.org>,
	Ingo Molnar <mingo@...e.hu>,
	Peter Zijlstra <peterz@...radead.org>,
	linux-kernel@...r.kernel.org,
	Masami Hiramatsu <masami.hiramatsu.pt@...achi.com>,
	2nddept-manager@....hitachi.co.jp,
	Paul Mackerras <paulus@...ba.org>
Subject: Re: [PATCH -tip v3 3/6] perf branch trace: print pid and command



On 04/01/11 09:13, Frederic Weisbecker wrote:
> On Mon, Mar 28, 2011 at 08:31:23AM -0600, David Ahern wrote:
>> On 03/28/11 04:34, Akihiro Nagai wrote:
>>>> from is sample->ip? to is sample->addr? In the above example
>>>> 0x39d3015260 is the value from sample->addr, 1526f is sample->ip which
>>>> resolves to _dl_next_ld_env_entry from /lib64/ld-2.13.so.
>>> Yes.
>>> In this example, resolved address is only sample->ip (branch from).
>>> We need the resolved address of sample->addr (branch to) too, because
>>> both of them are addresses of execution code.
>>
>> Ok, now I understand. In that case add conversion of sample->addr to
>> symbols to perf-script.
> 
> I agree that we should rather use perf script for branch dumps.
> Sorry Akihiro, I think we suggested you to create this dedicated
> perf branch by the past. But then perf script became the vanilla dump
> tool in the middle and it seems more suitable today.
> 
> We can still create a perf branch later in order to produce some more
> advanced post-processing tools. But for sample dumps perf script (which starts
> to show itself as a misnomer BTW) seems to be the right place.

perf-dump?

> 
> So, in this context, if we have PERF_SAMPLE_ADDR, we are going to always
> follow the ip with a "=>" and then resolve the address, etc...
> 
> Yeah it makes sense for this default mode. But what about when we'll want
> a function graph kind of output? This will require a totally different
> layout. Also PERF_SAMPLE_ADDR may be used for different context in the
> future.
> 
> Perhaps we want a kind of per evsel callback that makes its own
> interpretation of the pid/tid/dso/sym/etc... options asked by the
> user?

The print addr function can take the evsel as an input. It includes the
event type which can be used to decide what the address means.

> 
> But well, we can start simple and make and just do the => trick
> if we have PERF_SAMPLE_ADDR and resolve addr if the user asked
> the sym. Then when we have the graph output, have these per evsel
> display callbacks.

There is another email thread about page faults. The user wants sample
address resolved to symbols. I was going to look into it next week when
I get back from vacation.
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