From mboxrd@z Thu Jan 1 00:00:00 1970 Message-ID: <478CAB25.30300@grupopie.com> Date: Tue, 15 Jan 2008 12:46:29 +0000 From: Paulo Marques MIME-Version: 1.0 Subject: Re: [RFC] mmaped copy too slow? References: <20080115100450.1180.KOSAKI.MOTOHIRO@jp.fujitsu.com> In-Reply-To: <20080115100450.1180.KOSAKI.MOTOHIRO@jp.fujitsu.com> Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org Return-Path: To: KOSAKI Motohiro Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org, Rik van Riel , Andrew Morton List-ID: KOSAKI Motohiro wrote: > Hi > > at one point, I found the large file copy speed was different depending on > the copy method. > > I compared below method > - read(2) and write(2). > - mmap(2) x2 and memcpy. > - mmap(2) and write(2). > > in addition, effect of fadvice(2) and madvice(2) is checked. > > to a strange thing, > - most faster method is read + write + fadvice. > - worst method is mmap + memcpy. One thing you could also try is to pass MAP_POPULATE to mmap so that the page tables are filled in at the time of the mmap, avoiding a lot of page faults later. Just my 2 cents, -- Paulo Marques - www.grupopie.com "All I ask is a chance to prove that money can't make me happy." -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org