From: Joe Perches Subject: Re: [PATCH] Performance Improvement in CRC16 Calculations. Date: Fri, 10 Aug 2018 12:23:06 -0700 Message-ID: <9b5b906f42dfab78f382c90f66851717d258a15d.camel@perches.com> References: <1533928331-21303-1-git-send-email-jeff.lien@wdc.com> Mime-Version: 1.0 Content-Type: text/plain; charset="ISO-8859-1" Content-Transfer-Encoding: 7bit Cc: herbert@gondor.apana.org.au, tim.c.chen@linux.intel.com, martin.petersen@oracle.com, david.darrington@wdc.com, jeff.furlong@wdc.com To: Jeff Lien , linux-kernel@vger.kernel.org, linux-crypto@vger.kernel.org, linux-block@vger.kernel.org, linux-scsi@vger.kernel.org Return-path: In-Reply-To: <1533928331-21303-1-git-send-email-jeff.lien@wdc.com> Sender: linux-kernel-owner@vger.kernel.org List-Id: linux-crypto.vger.kernel.org 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. > diff --git a/crypto/crct10dif_common.c b/crypto/crct10dif_common.c [] trivia: > +static const __u16 t10_dif_crc_table[16][256] = { > + { > + 0x0000u, 0x8BB7u, 0x9CD9u, 0x176Eu, 0xB205u, 0x39B2u, 0x2EDCu, 0xA56Bu, All the 'u's are unnecessary visual noise.