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

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Date:	Fri, 17 Jun 2011 17:15:12 +0200
From:	Frederic Weisbecker <fweisbec@...il.com>
To:	David Ahern <dsahern@...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 Fri, Jun 17, 2011 at 08:23:01AM -0600, David Ahern wrote:
> 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?

This can make sense, I can figure out some cases where such granularity can be
useful. Branch recording doesn't care about recording period for example I think.

> 
> 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.

Thanks a lot :)
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