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Re: copy_from_user_page/copy_to_user_page fix

To: Atsushi Nemoto <anemo@mba.ocn.ne.jp>
Subject: Re: copy_from_user_page/copy_to_user_page fix
From: Ralf Baechle <ralf@linux-mips.org>
Date: Wed, 9 Feb 2005 19:10:44 +0100
Cc: linux-mips@linux-mips.org
In-reply-to: <20050209.225256.92587183.anemo@mba.ocn.ne.jp>
Original-recipient: rfc822;linux-mips@linux-mips.org
References: <20050209.184947.30439119.nemoto@toshiba-tops.co.jp> <20050209125105.GA27875@linux-mips.org> <20050209.225256.92587183.anemo@mba.ocn.ne.jp>
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On Wed, Feb 09, 2005 at 10:52:56PM +0900, Atsushi Nemoto wrote:

> ralf> I'm going to apply this because it's a correct fix; the
> ralf> temporary mapping strategy as we've discussed for the dup_mmap
> ralf> problem would be preferable.
> 
> Thank you.  I agree that the temporary mapping will be more efficient
> though I chose a simple fix.  I suppose a performance requirement for
> ptrace() would be less than the dup_mmap (fork()).

People have come up with creative abuses for ptrace which actually make
it a performance critical path.  Especially UML should be mentioned in
this cathegory.  And we're talkign about a few thousand cycles differences
per ptrace invocation.

  Ralf

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