Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751771AbXAZXhs (ORCPT ); Fri, 26 Jan 2007 18:37:48 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1751778AbXAZXhs (ORCPT ); Fri, 26 Jan 2007 18:37:48 -0500 Received: from ug-out-1314.google.com ([66.249.92.174]:17137 "EHLO ug-out-1314.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751771AbXAZXhr (ORCPT ); Fri, 26 Jan 2007 18:37:47 -0500 DomainKey-Signature: a=rsa-sha1; c=nofws; d=googlemail.com; s=beta; h=received:from:to:subject:date:user-agent:cc:references:in-reply-to:mime-version:content-type:content-transfer-encoding:content-disposition:message-id; b=FCPAa5lhAk4HI1kEihJRkQQgcRCSE5EcGeKWFeBByn0GkApm4Cw3trsjE1t/dlnkR0sg56HMP8kWWZ8PoyDiOp4tyDtRdlSTC6r1Q3vtkTCn1RHiOVMWDn5hL96E/7OXd3NVoDS64OuOaSmAmj9QYnQ0hpuFbmXcQs37QiwmtLw= From: Denis Vlasenko To: Bill Davidsen Subject: Re: O_DIRECT question Date: Sat, 27 Jan 2007 00:35:31 +0100 User-Agent: KMail/1.8.2 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 References: <6d6a94c50701101857v2af1e097xde69e592135e54ae@mail.gmail.com> <200701252211.39017.vda.linux@googlemail.com> <45BA4720.5010406@tmr.com> In-Reply-To: <45BA4720.5010406@tmr.com> MIME-Version: 1.0 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: 7bit Content-Disposition: inline Message-Id: <200701270035.31285.vda.linux@googlemail.com> Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1157 Lines: 28 On Friday 26 January 2007 19:23, Bill Davidsen wrote: > 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. It is not required by any standard that I know. Kernel can be smarter and avoid that if it can. -- vda - 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/