linux-kernel - Re: [RFC PATCH 0/4] perf: Custom contexts

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Date:	Wed, 16 Mar 2011 14:53:15 +0100
From:	Frederic Weisbecker <fweisbec@...il.com>
To:	Peter Zijlstra <a.p.zijlstra@...llo.nl>
Cc:	LKML <linux-kernel@...r.kernel.org>,
	Arnaldo Carvalho de Melo <acme@...hat.com>,
	Paul Mackerras <paulus@...ba.org>,
	Stephane Eranian <eranian@...gle.com>,
	Steven Rostedt <rostedt@...dmis.org>,
	Masami Hiramatsu <masami.hiramatsu.pt@...achi.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	Hitoshi Mitake <mitake@....info.waseda.ac.jp>
Subject: Re: [RFC PATCH 0/4] perf: Custom contexts

On Tue, Mar 15, 2011 at 11:32:54PM +0100, Peter Zijlstra wrote:
> Right, so I don't much like the interface, two new ioctl()s and a flag
> of dubious use.

Do you think we need a new syscall for this new feature.
 
> How important is this recursive nature of the thing to you:
> 
> > It's supposed to support infinite combinations with starter having starters
> > themselves, plus filters, etc...
> 
> We've so far avoided recursion like that, we only have single level
> groups etc.

There is actually no recursivity of any sort that the kernel has to handle.
The starter/stopper links are never handled recursively. ie: there is no
loop walking through the entire chain of starter to starter to starter, etc...

It's always only handled between direct related event: starter and target, but
never further.

Only the final effect has recursion properties in the resulting count
or trace.
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