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Date:   Fri, 10 Aug 2018 16:02:23 -0400 (EDT)
From:   Nicolas Pitre <nicolas.pitre@linaro.org>
To:     Joe Perches <joe@perches.com>
cc:     Jeff Lien <jeff.lien@wdc.com>, linux-kernel@vger.kernel.org,
        linux-crypto@vger.kernel.org, linux-block@vger.kernel.org,
        linux-scsi@vger.kernel.org, herbert@gondor.apana.org.au,
        tim.c.chen@linux.intel.com, martin.petersen@oracle.com,
        david.darrington@wdc.com, jeff.furlong@wdc.com
Subject: Re: [PATCH] Performance Improvement in CRC16 Calculations.
In-Reply-To: <9b5b906f42dfab78f382c90f66851717d258a15d.camel@perches.com>
Message-ID: <nycvar.YSQ.7.76.1808101601110.13885@knanqh.ubzr>
References: <1533928331-21303-1-git-send-email-jeff.lien@wdc.com> <9b5b906f42dfab78f382c90f66851717d258a15d.camel@perches.com>
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On Fri, 10 Aug 2018, Joe Perches wrote:

> On Fri, 2018-08-10 at 14:12 -0500, Jeff Lien wrote:
> > This patch provides a performance improvement for the CRC16 calculations done in read/write
> > workloads using the T10 Type 1/2/3 guard field.  For example, today with sequential write
> > workloads (one thread/CPU of IO) we consume 100% of the CPU because of the CRC16 computation
> > bottleneck.  Today's block devices are considerably faster, but the CRC16 calculation prevents
> > folks from utilizing the throughput of such devices.  To speed up this calculation and expose
> > the block device throughput, we slice the old single byte for loop into a 16 byte for loop,
> > with a larger CRC table to match.  The result has shown 5x performance improvements on various
> > big endian and little endian systems running the 4.18.0 kernel version.
> 
> Thanks.
> 
> This seems a sensible tradeoff for the 4k text size increase.

More like 7.5KB.  Would be best if this was configurable so the small 
version remained available.


Nicolas