linux-kernel - RE: [patch v3 6/7] crc32: add-slicing-by-8.diff

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Date:	Wed, 10 Aug 2011 11:32:58 +0200
From:	Joakim Tjernlund <joakim.tjernlund@...nsmode.se>
To:	"Bob Pearson" <rpearson@...temfabricworks.com>
Cc:	akpm@...ux-foundation.org, fzago@...temfabricworks.com,
	linux@...izon.com, linux-kernel@...r.kernel.org
Subject: RE: [patch v3 6/7] crc32: add-slicing-by-8.diff

"Bob Pearson" <rpearson@...temfabricworks.com> wrote on 2011/08/09 22:52:34:

> From: "Bob Pearson" <rpearson@...temfabricworks.com>
> To: "'Joakim Tjernlund'" <joakim.tjernlund@...nsmode.se>
> Cc: <akpm@...ux-foundation.org>, <fzago@...temfabricworks.com>, <linux@...izon.com>, <linux-kernel@...r.kernel.org>
> Date: 2011/08/09 22:52
> Subject: RE: [patch v3 6/7] crc32: add-slicing-by-8.diff
>
> > >    - extend largest BITS size from 32 to 64
> > >    - extend table from tab[4][256] to tab[8][256]
> > >    - change algorithm to align on 8 byte boundary
> > >      (it was noted that all that is really required
> > >      is that the inner loop must comsume 8 bytes.
> > >      As written it can start on even or odd 4 byte
> > >      boundary.)
> > So why not do that in the code too?
> >
>
> I did the experiment with the random test set and it is a couple of % faster
> so I made the change. I had thought that it wouldn't make a measurable
> difference.

That could depend on how the test data table is aligned. What if you change
the alignment of the table?

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