From: Nicolas Pitre Subject: Re: [PATCH] Performance Improvement in CRC16 Calculations. Date: Fri, 10 Aug 2018 16:00:12 -0400 (EDT) Message-ID: References: <1533928331-21303-1-git-send-email-jeff.lien@wdc.com> Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Cc: 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 To: Jeff Lien 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, 10 Aug 2018, 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. You are nevertheless increasing the kernel size by 7.5 KB. Could the small table still be preserved with a config option for those who require small more than fast? That could look like: static const __u16 t10_dif_crc_table[][256] = { { [...] }, #ifndef CONFIG_CRC16_SMALL { [...] [...] }, #endif }; and the code to suit. Nicolas