linux-kernel - Re: x86, ptrace: support for branch trace store(BTS)

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Message-ID: <20071213102939.GS8977@elte.hu>
Date:	Thu, 13 Dec 2007 11:29:39 +0100
From:	Ingo Molnar <mingo@...e.hu>
To:	"Metzger, Markus T" <markus.t.metzger@...el.com>
Cc:	ak@...e.de, hpa@...or.com, linux-kernel@...r.kernel.org,
	tglx@...utronix.de, markus.t.metzger@...il.com,
	"Siddha, Suresh B" <suresh.b.siddha@...el.com>, roland@...hat.com,
	akpm@...ux-foundation.org, mtk.manpages@...il.com,
	Alan Stern <stern@...land.harvard.edu>
Subject: Re: x86, ptrace: support for branch trace store(BTS)


* Metzger, Markus T <markus.t.metzger@...el.com> wrote:

> Users who want to process that huge amount of data would be better off 
> using a file-based approach (well, if it cannot be held in physical 
> memory, they will spend most of their time swapping, anyway). Those 
> users would typically wait for the 'buffer full' event and drain the 
> buffer into a file - whether this is the real buffer or a bigger 
> virtual buffer.
> 
> The two-buffer approach would only benefit users who want to hold the 
> full profile in memory - or who want to stall the debuggee until they 
> processed or somehow compressed the data collected so far. Those 
> approaches would not scale for very big profiles. The small profile 
> cases would already be covered with a reasonably big real buffer.

well, the two-buffer approach would just be a general API with no 
limitations. It would make the internal buffer mostly a pure performance 
detail.

	Ingo
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