From mboxrd@z Thu Jan 1 00:00:00 1970 From: Andi Kleen Subject: Re: Re: Reducing impact of save/restore/dump on Dom0 Date: Wed, 7 Feb 2007 13:58:27 +0100 Message-ID: <200702071358.27540.ak@suse.de> References: <342BAC0A5467384983B586A6B0B3767104A69BB9@EXNA.corp.stratus.com> <8A87A9A84C201449A0C56B728ACF491E04F480@liverpoolst.ad.cl.cam.ac.uk> Mime-Version: 1.0 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <8A87A9A84C201449A0C56B728ACF491E04F480@liverpoolst.ad.cl.cam.ac.uk> Content-Disposition: inline List-Unsubscribe: , List-Post: List-Help: List-Subscribe: , Sender: xen-devel-bounces@lists.xensource.com Errors-To: xen-devel-bounces@lists.xensource.com To: Ian Pratt Cc: "Graham, Simon" , xen-devel@lists.xensource.com List-Id: xen-devel@lists.xenproject.org > It's pretty easy for us to arrange that everything is page aligned. If > there was a measurable performance advantage using o_direct rather than > madvise/fadvise it probably makes sense to use it -- I can't see > o_direct going away any time soon. O_DIRECT won't do any write behind, so unless you do very aggressive IO (large IO requests, threads or aio so you do useful work during the disk write latency) it will be likely slower. Similar for read -- it won't do any readahead which you would need to do by yourself. It's really not a very good idea for most non database applications. -Andi