linux-kernel - Re: [PATCH v6 00/10] crc32

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Message-ID: <OFF9DA484B.B301BBA9-ONC1257900.0033D34C-C1257900.00346FEF@transmode.se>
Date:	Sat, 3 Sep 2011 11:32:45 +0200
From:	Joakim Tjernlund <joakim.tjernlund@...nsmode.se>
To:	Andrew Morton <akpm@...ux-foundation.org>
Cc:	fzago@...temfabricworks.com, George Spelvin <linux@...izon.com>,
	linux-kernel@...r.kernel.org,
	Bob Pearson <rpearson@...temfabricworks.com>
Subject: Re: [PATCH v6 00/10] crc32


Andrew Morton <akpm@...ux-foundation.org> wrote on 2011/09/03 01:50:20:
>
> On Wed, 31 Aug 2011 17:29:32 -0500
> Bob Pearson <rpearson@...temfabricworks.com> wrote:
>
> > This is an attempt to resolve all the issues that were left in the last review.
> > There is one proposed change that is still causing a difference of opinion
> > which has to do with the form of the loops and their performance on x86 and ppc
> > This version has the change to the form that runs faster on x86 as an ifdef.
> >
> > This patch series provides improved performance for computing the crc32
> > polynomial on common hardware by adding the Slicing-by-8 algorithm to the
> > existing algorithms already included. The new algorithm is very closely
> > related to the existing algorithm so the extension requires small changes
> > to implement.  Additionally it cleans up some warnings in the existing
> > code and adds a kernel mode optional self test to replace the existing
> > user mode self test.
> >
> > A description of the existing and new algorithm is included in
> > Documentation/crc32.txt.
>
> So...  are the crc wars over yet?  I hope it's safe to look at the
> patches now ;)

Hehe, not sure :) I got side tracked with other things and haven't had time
to look into this last series.

>
> Please see Documentation/SubmittingPatches Section 15's discussion of
> patch Subject: lines.
>
> Is there any code in the kernel which uses the crc code so much that we
> actually care about its performance?

Sure, JFFS2/UBIFS/LogFS uses it heavily. SCTP too although it uses CRC32c, the
SW impl. of CRC32c should be moved to the same place as crc32.c

 Jocke

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