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=-2.2 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_PASS,UNPARSEABLE_RELAY,URIBL_BLOCKED,USER_AGENT_MUTT autolearn=ham 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 E4A5FC4321E for ; Fri, 7 Sep 2018 05:08:17 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 901EE20869 for ; Fri, 7 Sep 2018 05:08:17 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 901EE20869 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=c-sky.com 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 S1727593AbeIGJrZ (ORCPT ); Fri, 7 Sep 2018 05:47:25 -0400 Received: from smtp2200-217.mail.aliyun.com ([121.197.200.217]:46629 "EHLO smtp2200-217.mail.aliyun.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725805AbeIGJrZ (ORCPT ); Fri, 7 Sep 2018 05:47:25 -0400 X-Alimail-AntiSpam: AC=CONTINUE;BC=0.07528035|-1;CH=green;FP=0|0|0|0|0|-1|-1|-1;HT=e02c03310;MF=ren_guo@c-sky.com;NM=1;PH=DS;RN=11;RT=11;SR=0;TI=SMTPD_---.CnYzP-y_1536296883; Received: from localhost(mailfrom:ren_guo@c-sky.com fp:SMTPD_---.CnYzP-y_1536296883) by smtp.aliyun-inc.com(10.147.41.138); Fri, 07 Sep 2018 13:08:03 +0800 Date: Fri, 7 Sep 2018 13:08:02 +0800 From: Guo Ren To: Arnd Bergmann Cc: linux-arch , Linux Kernel Mailing List , Thomas Gleixner , Daniel Lezcano , Jason Cooper , c-sky_gcc_upstream@c-sky.com, gnu-csky@mentor.com, Thomas Petazzoni , wbx@uclibc-ng.org, Greentime Hu Subject: Re: [PATCH V3 13/26] csky: Library functions Message-ID: <20180907050801.GA13356@guoren-Inspiron-7460> References: <37f9bd824ede529fdab291a40eef3415f99ec8aa.1536138304.git.ren_guo@c-sky.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.5.24 (2015-08-30) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, Sep 06, 2018 at 04:24:59PM +0200, Arnd Bergmann wrote: > On Wed, Sep 5, 2018 at 2:08 PM Guo Ren wrote: > > > --- /dev/null > > +++ b/arch/csky/abiv1/memset.c > > @@ -0,0 +1,38 @@ > > +// SPDX-License-Identifier: GPL-2.0 > > +// Copyright (C) 2018 Hangzhou C-SKY Microsystems co.,ltd. > > +#include > > + > > +void *memset(void *dest, int c, size_t l) > > +{ > > + char *d = dest; > > + int ch = c; > > + int tmp; > > + > > + if ((long)d & 0x3) > > + while (l--) *d++ = ch; > > + else { > > + ch &= 0xff; > > + tmp = (ch | ch << 8 | ch << 16 | ch << 24); > > + > > + while (l >= 16) { > > + *(((long *)d)) = tmp; > > + *(((long *)d)+1) = tmp; > > + *(((long *)d)+2) = tmp; > > + *(((long *)d)+3) = tmp; > > + l -= 16; > > + d += 16; > > + } > > + > > + while (l > 3) { > > + *(((long *)d)) = tmp; > > + d = d + 4; > > + l -= 4; > > + } > > + > > + while (l) { > > + *d++ = ch; > > + l--; > > + } > > + } > > + return dest; > > +} > > I see that we have a trivial memset() implementation in lib/string.c, but yours > seems to be better optimized. Where did you get it from? We write it for our ck610 to improve the performance, but I think a lot of other arch done it in asm style. > Is this a version > that works particularly well on C-Sky, or is this a generic optimized memset > that others could use as well? We only test it on C-SKY, but I think it will also work better on other arch CPU than current lib/string.c memset implement. I see that in lib/string.c: void *memset(void *s, int c, size_t count) { char *xs = s; while (count--) *xs++ = c; return s; } The most problem is "char *xs;" and it will cause "st.b" in asm. "st.b" is very slow. Our key improvement is: > > + *(((long *)d)) = tmp; > > + *(((long *)d)+1) = tmp; > > + *(((long *)d)+2) = tmp; > > + *(((long *)d)+3) = tmp; It will cause SOC AXI burst transfer. > In the latter case, we could add it to > lib/string.c and let architectures select it in place of the triivial version. Good idea. Guo Ren