linux-kernel - Re: [PATCH 4/6] perf record: add time-of-day option

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Date:	Fri, 17 Jun 2011 08:23:01 -0600
From:	David Ahern <dsahern@...il.com>
To:	Frederic Weisbecker <fweisbec@...il.com>
CC:	linux-perf-users@...r.kernel.org, linux-kernel@...r.kernel.org,
	acme@...stprotocols.net, mingo@...e.hu, peterz@...radead.org,
	paulus@...ba.org, tglx@...utronix.de
Subject: Re: [PATCH 4/6] perf record: add time-of-day option

On 06/17/2011 08:14 AM, Frederic Weisbecker wrote:
> 
> So I feel uncomfortable with this tod_sample_type hack. I think we can't really continue
> with this fixed sample_type per session given the kind of hacks that involves.
> 
> One thing we could do is to split session->sample_type into an array with one sample
> type per event type (hardware, breakpoint, software, tracepoint).
> 
> And then each builtin tool can provide their constraints on top of these values:
> 
> - builtin-report wants sample_type[HARDWARE] == sample_type[SOFTWARE] == sample_type[TRACEPOINT] == sample_type[BREAKPOINT]
>   although that may be tunable by the time but we can start with that.
> - builtin-script has no specific constraints, except that sample_type[i] meets what the user passed as a parameter
> - etc..
> 
> Constraints can probably default to sample_type[i] == sample_type[i+1] to mimic the current behaviour. Then tools
> can override that.
> 
> What do you think?

I started working on sample_type refactoring right after sending this
patchset (though I got sidetracked). Each evsel in the list has a
perf_attr struct which has a sample_type. Why not use that which allows
events to have their own sample type - versus a type per event type?

I'll see if I can get back to it in the next few days and get a better
idea of the pain involved with the refactoring.

David
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