linux-kernel - Re: [PATCH v4 02/22] perf: Add AUX area to ring buffer for raw data streams

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Message-ID: <20141007151515.GA5850@twins.programming.kicks-ass.net>
Date:	Tue, 7 Oct 2014 17:15:15 +0200
From:	Peter Zijlstra <peterz@...radead.org>
To:	Alexander Shishkin <alexander.shishkin@...ux.intel.com>
Cc:	Ingo Molnar <mingo@...hat.com>, linux-kernel@...r.kernel.org,
	Robert Richter <rric@...nel.org>,
	Frederic Weisbecker <fweisbec@...il.com>,
	Mike Galbraith <efault@....de>,
	Paul Mackerras <paulus@...ba.org>,
	Stephane Eranian <eranian@...gle.com>,
	Andi Kleen <ak@...ux.intel.com>, kan.liang@...el.com
Subject: Re: [PATCH v4 02/22] perf: Add AUX area to ring buffer for raw data
 streams

On Tue, Oct 07, 2014 at 12:52:49AM +0300, Alexander Shishkin wrote:
> Peter Zijlstra <peterz@...radead.org> writes:

> > No, and I think I realized this after sending that email, but at the
> > time I figured there was another way to do it. Of course, now that
> > several weeks have passed I cannot for the life of me remember what it
> > was.
> >
> > Lemme go over these patches again to refresh my mind and maybe I'll
> > remember.
> 
> Yes, ring buffer can keep a refcount for the aux_priv object, which is
> grabbed once at mmap and once at perf_aux_output_begin() and released
> accordingly and whichever drops the refcount to zero calls
> pmu::free_aux. No need to grab page->_count and driver is a bit simpler.

Yes, I suppose that'll work just fine.
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