Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1161151AbXAZSYu (ORCPT ); Fri, 26 Jan 2007 13:24:50 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1161150AbXAZSYu (ORCPT ); Fri, 26 Jan 2007 13:24:50 -0500 Received: from main.gmane.org ([80.91.229.2]:41554 "EHLO ciao.gmane.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1161149AbXAZSYs (ORCPT ); Fri, 26 Jan 2007 13:24:48 -0500 X-Injected-Via-Gmane: http://gmane.org/ To: linux-kernel@vger.kernel.org From: Bill Davidsen Subject: Re: O_DIRECT question Date: Fri, 26 Jan 2007 13:23:28 -0500 Message-ID: <45BA4720.5010406@tmr.com> References: <6d6a94c50701101857v2af1e097xde69e592135e54ae@mail.gmail.com> <45B90D19.60106@cfl.rr.com> <45B916F2.4070906@tls.msk.ru> <200701252211.39017.vda.linux@googlemail.com> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit X-Complaints-To: usenet@sea.gmane.org Cc: Michael Tokarev , Phillip Susi , Linus Torvalds , Viktor , Aubrey , Hua Zhong , Hugh Dickins , linux-kernel@vger.kernel.org, hch@infradead.org, kenneth.w.chen@in X-Gmane-NNTP-Posting-Host: mail.tmr.com User-Agent: Mozilla/5.0 (X11; U; Linux i686; en-US; rv:1.8.0.8) Gecko/20061105 SeaMonkey/1.0.6 In-Reply-To: <200701252211.39017.vda.linux@googlemail.com> Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1126 Lines: 22 Denis Vlasenko wrote: > On Thursday 25 January 2007 21:45, Michael Tokarev wrote: >> Phillip Susi wrote: >>> Denis Vlasenko wrote: >>>> You mean "You can use aio_write" ? >>> Exactly. You generally don't use O_DIRECT without aio. Combining the >>> two is what gives the big win. >> Well, it's not only aio. Multithreaded I/O also helps alot -- all this, >> say, to utilize a raid array with many spindles. >> >> But even single-threaded I/O but in large quantities benefits from O_DIRECT >> significantly, and I pointed this out before. > > Which shouldn't be true. There is no fundamental reason why > ordinary writes should be slower than O_DIRECT. > Other than the copy to buffer taking CPU and memory resources. -- Bill Davidsen "We have more to fear from the bungling of the incompetent than from the machinations of the wicked." - from Slashdot - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/