Re: [PATCH] Performance Improvement in CRC16 Calculations.

From: Nicolas Pitre
Date: Fri Aug 10 2018 - 16:02:30 EST

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.