From: Miao Xie Subject: Re: [PATCH V2 1/3] lib: introduce some memory copy macros and functions Date: Wed, 08 Sep 2010 21:32:42 +0800 Message-ID: <4C87907A.2040500@cn.fujitsu.com> References: <46238.91.60.152.217.1283948365.squirrel@www.firstfloor.org> <4C878823.60709@cn.fujitsu.com> <20100908150519.2f9fe283@basil.nowhere.org> Reply-To: miaox@cn.fujitsu.com Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Cc: Peter Zijlstra , Ingo Molnar , Andrew Morton , "Theodore Ts'o" , Linux Kernel , Linux Ext4 , Linux Btrfs To: Andi Kleen Return-path: In-Reply-To: <20100908150519.2f9fe283@basil.nowhere.org> Sender: linux-btrfs-owner@vger.kernel.org List-Id: linux-ext4.vger.kernel.org On Wed, 8 Sep 2010 15:05:19 +0200, Andi Kleen wrote: > On Wed, 08 Sep 2010 20:57:07 +0800 > Miao Xie wrote: > >> On Wed, 8 Sep 2010 14:19:25 +0200 (cest), Andi Kleen wrote: >>> >>>> According to the data, the length of the most copies is>=128. >>> >>> Thanks for the data. Large is easier to optimize than small, that's >>> good. >>> >>> Could you also measure how many memsets need the backwards copy? ^^^^^^^ :-) >>> (should be easy to add) >> >> I think memset doesn't need the backwards copy. > > I meant for memmove of course. Obviously memset doesn't need a backwards > copy. That was just the only thing the script didn't measure because > the original version didn't have memmove support. memmove total 5224252 [snip] forward copy value |-------------------------------------------------- count 0 |@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@ 980253 backward copy value |-------------------------------------------------- count 0 |@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@ 4243999 the backward copy is much more than the forward copy. Thanks Miao