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

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Message-ID: <877hip4et0.fsf@basil.nowhere.org>
Date:	Mon, 13 Sep 2010 21:35:39 +0200
From:	Andi Kleen <andi@...stfloor.org>
To:	eranian@...gle.com
Cc:	linux-kernel@...r.kernel.org, peterz@...radead.org, mingo@...e.hu,
	paulus@...ba.org, davem@...emloft.net, fweisbec@...il.com,
	perfmon2-devel@...ts.sf.net, eranian@...il.com,
	robert.richter@....com, markus.t.metzger@...el.com
Subject: Re: [PATCH] perf_events: improve DS/BTS/PEBS buffer allocation

Stephane Eranian <eranian@...gle.com> writes:

> The DS, BTS, and PEBS memory regions were allocated using kzalloc(), i.e.,
> requesting contiguous physical memory. There is no such restriction on
> DS, PEBS and BTS buffers. Using kzalloc() could lead to error in case
> no contiguous physical memory is available. BTS is requesting 64KB,
> thus it can cause issues. PEBS is currently only requesting one page.
> Both PEBS and BTS are static buffers allocated for each CPU at the
> first user. When the last user exists, the buffers are released.

DS supports page tables, but I have some doubts it really 
supports page faults. vmalloc today does page faults. 

I think the change is a good idea, but it will need vmalloc_sync_all()
everywhere.

-Andi

-- 
ak@...ux.intel.com -- Speaking for myself only.
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