From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=1.0 required=3.0 tests=DKIM_SIGNED,DKIM_VALID, DKIM_VALID_AU,FSL_HELO_FAKE,MAILING_LIST_MULTI,SPF_PASS,T_DKIMWL_WL_HIGH, USER_AGENT_MUTT autolearn=no autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id A7416C4646D for ; Fri, 10 Aug 2018 20:16:07 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 5D1922242A for ; Fri, 10 Aug 2018 20:16:07 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=kernel.org header.i=@kernel.org header.b="pppdjJNw" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 5D1922242A Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=kernel.org Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727427AbeHJWrZ (ORCPT ); Fri, 10 Aug 2018 18:47:25 -0400 Received: from mail.kernel.org ([198.145.29.99]:37670 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726834AbeHJWrZ (ORCPT ); Fri, 10 Aug 2018 18:47:25 -0400 Received: from gmail.com (unknown [104.132.51.88]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id 4250622429; Fri, 10 Aug 2018 20:16:03 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1533932163; bh=FR5Ywpe30dxkzAaniIGx8R0LRGRfGXpHYSDACxRskc0=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=pppdjJNwVFsJ9hQeXCZPRnQztzQHvXodcecKqVuVZBT2syg79WWxeWXypVlK8tDYm tjMT9s/B4kfFmSc8JHbgMtgu+zRYveg0AXzKhiiuEAi1/fI7OVXKoOCVnCL8Lt+G0t hJLxg3pBWLLYQQk3jrb3uSfKAPPz5uvt/4GcghK8= Date: Fri, 10 Aug 2018 13:16:02 -0700 From: Eric Biggers To: Jeff Lien 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 Subject: Re: [PATCH] Performance Improvement in CRC16 Calculations. Message-ID: <20180810201601.GA80850@gmail.com> References: <1533928331-21303-1-git-send-email-jeff.lien@wdc.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1533928331-21303-1-git-send-email-jeff.lien@wdc.com> User-Agent: Mutt/1.10.1+60 (20b17ca5) (2018-08-02) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, Aug 10, 2018 at 02:12:11PM -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. > > FIO Sequential Write, 64K Block Size, Queue Depth 64 > BE Base Kernel: bw=201.5 MiB/s > BE Modified CRC Calc: bw=968.1 MiB/s > 4.80x performance improvement > > LE Base Kernel: bw=357 MiB/s > LE Modified CRC Calc: bw=1964 MiB/s > 5.51x performance improvement > > FIO Sequential Read, 64K Block Size, Queue Depth 64 > BE Base Kernel: bw=611.2 MiB/s > BE Modified CRC calc: bw=684.9 MiB/s > 1.12x performance improvement > > LE Base Kernel: bw=797 MiB/s > LE Modified CRC Calc: bw=2730 MiB/s > 3.42x performance improvement Did you also test the slice-by-4 (requires 2048-byte table) and slice-by-8 (requires 4096-byte table) methods? Your proposal is slice-by-16 (requires 8192-byte table); the original was slice-by-1 (requires 512-byte table). > __u16 crc_t10dif_generic(__u16 crc, const unsigned char *buffer, size_t len) > { > - unsigned int i; > + const __u8 *i = (const __u8 *)buffer; > + const __u8 *i_end = i + len; > + const __u8 *i_last16 = i + (len / 16 * 16); 'i' is normally a loop counter, not a pointer. Use 'p', 'p_end', and 'p_last16'. > > - for (i = 0 ; i < len ; i++) > - crc = (crc << 8) ^ t10_dif_crc_table[((crc >> 8) ^ buffer[i]) & 0xff]; > + for (; i < i_last16; i += 16) { > + crc = t10_dif_crc_table[15][i[0] ^ (__u8)(crc >> 8)] ^ > + t10_dif_crc_table[14][i[1] ^ (__u8)(crc >> 0)] ^ > + t10_dif_crc_table[13][i[2]] ^ > + t10_dif_crc_table[12][i[3]] ^ > + t10_dif_crc_table[11][i[4]] ^ > + t10_dif_crc_table[10][i[5]] ^ > + t10_dif_crc_table[9][i[6]] ^ > + t10_dif_crc_table[8][i[7]] ^ > + t10_dif_crc_table[7][i[8]] ^ > + t10_dif_crc_table[6][i[9]] ^ > + t10_dif_crc_table[5][i[10]] ^ > + t10_dif_crc_table[4][i[11]] ^ > + t10_dif_crc_table[3][i[12]] ^ > + t10_dif_crc_table[2][i[13]] ^ > + t10_dif_crc_table[1][i[14]] ^ > + t10_dif_crc_table[0][i[15]]; > + } Please indent this properly. crc = t10_dif_crc_table[15][i[0] ^ (__u8)(crc >> 8)] ^ t10_dif_crc_table[14][i[1] ^ (__u8)(crc >> 0)] ^ t10_dif_crc_table[13][i[2]] ^ t10_dif_crc_table[12][i[3]] ^ t10_dif_crc_table[11][i[4]] ^ ... - Eric