linux-kernel - Re: [PATCH 1/2] perf: Add persistent event facilities

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Date:	Fri, 18 May 2012 13:24:23 +0200
From:	Peter Zijlstra <peterz@...radead.org>
To:	Borislav Petkov <bp@...64.org>
Cc:	Frederic Weisbecker <fweisbec@...il.com>,
	Ingo Molnar <mingo@...e.hu>,
	Steven Rostedt <rostedt@...dmis.org>,
	LKML <linux-kernel@...r.kernel.org>,
	Borislav Petkov <borislav.petkov@....com>
Subject: Re: [PATCH 1/2] perf: Add persistent event facilities

On Fri, 2012-05-18 at 13:03 +0200, Borislav Petkov wrote:
> >  - you allow an arbitrary place in debugfs; this might make finding
> > them 'interesting'. Should we put them all in the same place?
> 
> My take on this is that we want to be able to make the same events we
> have now, persistent. Basically not trace for the duration of a child
> process but in a process-agnostic way, system-wide.

This would argue against per-task persistent events.. 

> In that case, we probably want to be able to mark events as persistent,
> maybe add another node in debugfs:
> 
> (debugfs)/tracing/events/mce/mce_record/attr
> 
> which can be used for flags or whatever, or something to that effect... 

( while mce is a user of persistent events, it seems to me in general
persistent events should not be related to mce )

However you raise a valid point about keeping track of what events are
spooled into that buffer.

Note the plural there, it might be very desirable to allow multiple
events into a single persistent buffer.


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