linux-kernel - Re: [PATCH] perf_events: improve DS/BTS/PEBS buffer allocation

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Message-ID: <1284406463.2275.423.camel@laptop>
Date:	Mon, 13 Sep 2010 21:34:23 +0200
From:	Peter Zijlstra <peterz@...radead.org>
To:	Mathieu Desnoyers <mathieu.desnoyers@...icios.com>
Cc:	Stephane Eranian <eranian@...gle.com>,
	Frederic Weisbecker <fweisbec@...il.com>,
	linux-kernel@...r.kernel.org, mingo@...e.hu, paulus@...ba.org,
	davem@...emloft.net, perfmon2-devel@...ts.sf.net,
	eranian@...il.com, robert.richter@....com,
	"markus.t.metzger" <markus.t.metzger@...el.com>
Subject: Re: [PATCH] perf_events: improve DS/BTS/PEBS buffer allocation

On Mon, 2010-09-13 at 15:31 -0400, Mathieu Desnoyers wrote:
> > Ok, so can we play the same trick you're playing with the sampling
> > buffer, i.e., you use alloc_pages_node() for one page at a time, and
> > then you stitch them on demand via SW?
> 
> Well, a thought is striking me: it sounds like you are re-doing YAORB (short
> for Yet Another Ring Buffer, 

He's not.. the hardware needs a large (virtually) contiguous region to
poke data into, we need to read it out from NMI context.
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