From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932203AbeCKMAT (ORCPT ); Sun, 11 Mar 2018 08:00:19 -0400 Received: from mail-wm0-f67.google.com ([74.125.82.67]:34756 "EHLO mail-wm0-f67.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932126AbeCKMAR (ORCPT ); Sun, 11 Mar 2018 08:00:17 -0400 X-Google-Smtp-Source: AG47ELv1GerVbOz7Q6JTHWpdLALfdiRKKxNNSr9Uf8CRWEoUOXeITKt/7JEPC1IpYWixDgy7SfJqgg== Subject: Re: [RFC v2 05/83] Add NOVA filesystem definitions and useful helper routines. To: Andiry Xu , linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org, linux-nvdimm@lists.01.org Cc: dan.j.williams@intel.com, andy.rudoff@intel.com, coughlan@redhat.com, swanson@cs.ucsd.edu, david@fromorbit.com, jack@suse.com, swhiteho@redhat.com, miklos@szeredi.hu, andiry.xu@gmail.com, Andiry Xu , herbert@gondor.apana.org.au References: <1520705944-6723-1-git-send-email-jix024@eng.ucsd.edu> <1520705944-6723-6-git-send-email-jix024@eng.ucsd.edu> From: Nikolay Borisov Message-ID: <0924a2b3-6f21-4aaf-224d-2f5accc21d10@gmail.com> Date: Sun, 11 Mar 2018 14:00:13 +0200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101 Thunderbird/52.6.0 MIME-Version: 1.0 In-Reply-To: <1520705944-6723-6-git-send-email-jix024@eng.ucsd.edu> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org [Adding Herbert Xu to CC since he is the maintainer of the crypto subsys maintainer] On 10.03.2018 20:17, Andiry Xu wrote: > +static inline u32 nova_crc32c(u32 crc, const u8 *data, size_t len) > +{ > + u8 *ptr = (u8 *) data; > + u64 acc = crc; /* accumulator, crc32c value in lower 32b */ > + u32 csum; > + > + /* x86 instruction crc32 is part of SSE-4.2 */ > + if (static_cpu_has(X86_FEATURE_XMM4_2)) { > + /* This inline assembly implementation should be equivalent > + * to the kernel's crc32c_intel_le_hw() function used by > + * crc32c(), but this performs better on test machines. > + */ > + while (len > 8) { > + asm volatile(/* 64b quad words */ > + "crc32q (%1), %0" > + : "=r" (acc) > + : "r" (ptr), "0" (acc) > + ); > + ptr += 8; > + len -= 8; > + } > + > + while (len > 0) { > + asm volatile(/* trailing bytes */ > + "crc32b (%1), %0" > + : "=r" (acc) > + : "r" (ptr), "0" (acc) > + ); > + ptr++; > + len--; > + } > + > + csum = (u32) acc; > + } else { > + /* The kernel's crc32c() function should also detect and use the > + * crc32 instruction of SSE-4.2. But calling in to this function > + * is about 3x to 5x slower than the inline assembly version on > + * some test machines. That is really odd. Did you try to characterize why this is the case? Is it purely the overhead of dispatching to the correct backend function? That's a rather big performance hit. > + */ > + csum = crc32c(crc, data, len); > + } > + > + return csum; > +} > +