From mboxrd@z Thu Jan 1 00:00:00 1970 From: Pekka Enberg Subject: Re: [PATCH v3] kvm tools: Add QCOW level2 caching support Date: Fri, 03 Jun 2011 00:07:59 +0300 Message-ID: <1307048879.27309.3.camel@jaguar> References: <1307044916-18109-1-git-send-email-prasadjoshi124@gmail.com> Mime-Version: 1.0 Content-Type: text/plain; charset="ISO-8859-1" Content-Transfer-Encoding: 7bit Cc: mingo@elte.hu, kvm@vger.kernel.org, asias.hejun@gmail.com, gorcunov@gmail.com, levinsasha928@gmail.com, chaitanyakulkarni15@gmail.com, ashwini.kulkarni@gmail.com, anupshendkar@gmail.com To: Prasad Joshi Return-path: Received: from filtteri5.pp.htv.fi ([213.243.153.188]:52290 "EHLO filtteri5.pp.htv.fi" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752080Ab1FBVIC (ORCPT ); Thu, 2 Jun 2011 17:08:02 -0400 In-Reply-To: Sender: kvm-owner@vger.kernel.org List-ID: On Thu, 2011-06-02 at 21:57 +0100, Prasad Joshi wrote: > > Assuming the data is just mixed up, I'm not completely happy that > > we're making random seeks almost 5% slower. Any ideas why that's > > happening? > > Yes they are mixed. > > I am assuming, probably delay while caching. That doesn't make sense to me. Why would "caching delay" be significantly slower than the non-cached version where we do full read all the time? Maybe I didn't quite understand the code but that sounds like a bug lurking somewhere in the caching code - maybe we cache too much or something? Pekka