From: Andrew Morton <akpm@zip.com.au>
To: Mala Anand <manand@us.ibm.com>
Cc: Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
lse-tech@lists.sourceforge.net
Subject: Re: efficient copy_to_user and copy_from_user routines in Linux Kernel
Date: Tue, 25 Jun 2002 10:03:38 -0700 [thread overview]
Message-ID: <3D18A26A.73E6DD07@zip.com.au> (raw)
In-Reply-To: OFCB119CD8.D6AE7B3D-ON85256BE2.006AC911@raleigh.ibm.com
Mala Anand wrote:
>
> Here is a 2.5.19 patch that improves the performance of IA32 copy_to_user
> and copy_from_user routines used by :
>
> (1) tcpip protocol stack
> (2) file systems
>
This came up about a year back when zerocopy networking was merged.
Intel boxes started running more slowly purely because of the 8+8
alignment thing.
I changed tcp to use a different copy if either source or dest were
not eight-byte aligned, and found that the resulting improvement
across a mixed networking load was only 1%. Your numbers are higher,
so perhaps there are different alignments in the mix...
One question: have you tested on other CPU types? This problem is
very specific to Intel hardware. On AMD, the eight-byte alignement
artifact does not exist at all. It could be that your patch is not
desirable on such CPUs?
-
next prev parent reply other threads:[~2002-06-25 17:05 UTC|newest]
Thread overview: 14+ messages / expand[flat|nested] mbox.gz Atom feed top
2002-06-24 19:34 efficient copy_to_user and copy_from_user routines in Linux Kernel Mala Anand
2002-06-24 19:33 ` David S. Miller
2002-06-24 20:24 ` [Lse-tech] " Niels Christiansen
2002-06-25 17:03 ` Andrew Morton [this message]
2002-06-25 17:43 ` kuznet
2002-06-25 19:47 ` Andrew Morton
2002-06-25 21:46 ` Chris Friesen
2002-06-26 13:54 ` Hirokazu Takahashi
2002-06-25 18:58 ` [Lse-tech] " Niels Christiansen
2002-06-25 19:11 ` Dave Jones
2002-06-26 12:58 ` Andi Kleen
2002-06-26 14:50 ` Bill Hartner
-- strict thread matches above, loose matches on Subject: below --
2002-06-28 11:50 Mala Anand
2002-06-28 12:35 Mala Anand
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