linux-kernel - Re: [PATCH v4 04/22] perf: Add a capability for AUX_NO

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Message-ID: <20140908113129.GC6758@twins.programming.kicks-ass.net>
Date:	Mon, 8 Sep 2014 13:31:29 +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 04/22] perf: Add a capability for AUX_NO_SG pmus to do
 software double buffering

On Mon, Sep 08, 2014 at 02:07:22PM +0300, Alexander Shishkin wrote:
> Peter Zijlstra <peterz@...radead.org> writes:
> > In particular this looks like it will allocate double the total amount
> > of pages and 'loose' half of them. There is no corresponding code in the
> > free path to collect them.
> 
> This code makes the biggest high order allocation no bigger than half of
> the total requested size. Then, when I allocate the high-order chunks, I
> do a split_page() on them and everywhere else in the code they are
> treated as individual pages, including the free path. So this patch has
> no implication on freeing. Is this your concern?

Ah right. I completely misread the patch. Sorry for the noise.

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