linux-kernel - Re: [PATCH] RAID: add tilegx SIMD implementation of raid6

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Message-ID: <20130808092707.7149ee90@notabene.brown>
Date:	Thu, 8 Aug 2013 09:27:07 +1000
From:	NeilBrown <neilb@...e.de>
To:	Ken Steele <ken@...era.com>
Cc:	<linux-kernel@...r.kernel.org>, <linux-raid@...r.kernel.org>
Subject: Re: [PATCH] RAID: add tilegx SIMD implementation of raid6

On Wed, 7 Aug 2013 12:39:56 -0400 Ken Steele <ken@...era.com> wrote:

> This change adds TILE-Gx SIMD instructions to the software raid
> (md), modeling the Altivec implementation. This is only for Syndrome
> generation; there is more that could be done to improve recovery,
> as in the recent Intel SSE3 recovery implementation.
> 
> The code unrolls 8 times; this turns out to be the best on tilegx
> hardware among the set 1, 2, 4, 8 or 16.  The code reads one
> cache-line of data from each disk, stores P and Q then goes to the
> next cache-line.
> 
> The test code in sys/linux/lib/raid6/test reports 2008 MB/s data
> read rate for syndrome generation using 18 disks (16 data and 2
> parity). It was 1512 MB/s before this SIMD optimizations. This is
> running on 1 core with all the data in cache.
> 
> This is based on the paper The Mathematics of RAID-6.
> (http://kernel.org/pub/linux/kernel/people/hpa/raid6.pdf).
> 
> Signed-off-by: Ken Steele <ken@...era.com>
> Signed-off-by: Chris Metcalf <cmetcalf@...era.com>

Thanks.  Looks credible and you've obviously tested it so I've added it to my
queue for the next merge window.

One tiny little change I made:

>  clean:
>  	rm -f *.o *.a mktables mktables.c *.uc int*.c altivec*.c tables.c raid6test
> +	rm tilegx*.c

I made that "rm -f" for consistency.

Thanks,
NeilBrown


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