From mboxrd@z Thu Jan 1 00:00:00 1970 From: Avi Kivity Subject: Re: IO on guest is 20 times slower than host Date: Wed, 25 Mar 2009 18:35:31 +0200 Message-ID: <49CA5D53.1080401@redhat.com> References: <49CA5825.7030201@redhat.com> <4AC00930-1EBB-4704-94CF-29478D07F03A@yoderhome.com> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Cc: kvm@vger.kernel.org To: Kurt Yoder Return-path: Received: from mx2.redhat.com ([66.187.237.31]:57667 "EHLO mx2.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752861AbZCYQff (ORCPT ); Wed, 25 Mar 2009 12:35:35 -0400 In-Reply-To: <4AC00930-1EBB-4704-94CF-29478D07F03A@yoderhome.com> Sender: kvm-owner@vger.kernel.org List-ID: Kurt Yoder wrote: >> >> I get 141 MB/s on the same test (it only copies to memory anyway). >> Is your VM under memory pressure? > > I don't think so. The host has 128 GB of memory, and even the > pre-emptive kernel caching doesn't come close to filling it: > > me@host:~$ free > total used free shared buffers cached > Mem: 132043960 1742480 130301480 0 84628 826040 > -/+ buffers/cache: 831812 131212148 > Swap: 1048568 0 1048568 > > My /tmp should be physical disk in both cases. To be thorough, I also > ran the test while writing the output file to /, and got the same > results (5.7 MB/s on guest, 144 MB/s on host). Your guest is only assigned 256MB though. -- error compiling committee.c: too many arguments to function