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Date: Mon, 31 Dec 2001 20:47:43 +0100 (CET)
From: Dave Jones <davej@suse.de>
To: Andrew Morton <akpm@zip.com.au>
Cc: Manfred Spraul <manfred@colorfullife.com>,
        Linux Kernel <linux-kernel@vger.kernel.org>
Subject: Re: [patch] Prefetching file_read_actor()
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On Mon, 31 Dec 2001, Andrew Morton wrote:

> Looks like you'll need to do a __get_user() against the page to
> populate the tlb.  We're going to need it in the copy_to_user()
> anyway, so the cost is negligible.

Completly puzzled right now. Moving the prefetching to copy_to_user
(and doing the tlb preload & prefetching the whole chunk to be copied
(or cachesize if smaller)) results in a performance drop instead of a win.

My initial guess is that some of the callers of copy_to_user are
doing something that is harmed the prefetching.
(Maybe they are doing additional prefetch() calls)

Dave

-- 
| Dave Jones.        http://www.codemonkey.org.uk
| SuSE Labs

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