From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932472AbZBEBjE (ORCPT ); Wed, 4 Feb 2009 20:39:04 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1761968AbZBEBi2 (ORCPT ); Wed, 4 Feb 2009 20:38:28 -0500 Received: from yx-out-2324.google.com ([74.125.44.29]:53488 "EHLO yx-out-2324.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1762154AbZBEBi0 (ORCPT ); Wed, 4 Feb 2009 20:38:26 -0500 DomainKey-Signature: a=rsa-sha1; c=nofws; d=gmail.com; s=gamma; h=message-id:date:from:user-agent:mime-version:newsgroups:to:cc :subject:references:in-reply-to:content-type :content-transfer-encoding; b=snasCPMnCu4OXVb4wANZJHpqI/aYkr0P8veoIYLrt9YBPsYqMiWomXKserbsw5w/dx 3zJOhY/HLh0vOyTd9a/xsVw5geDzIVE8mDq/zcIVOqbQILmgEypWKEfNPXbwCgAUbqO3 vXyIYL3KEMkwuJmSCGtl/e68ox0pe1mghVEcU= Message-ID: <498A430E.1040809@gmail.com> Date: Wed, 04 Feb 2009 19:38:22 -0600 From: Robert Hancock User-Agent: Thunderbird 2.0.0.19 (X11/20090105) MIME-Version: 1.0 Newsgroups: gmane.linux.kernel To: Michael Monnerie CC: linux-kernel@vger.kernel.org Subject: Re: Poor performance on cp on kernel 2.6.27.7-9-xen (openSUSE 11.1) References: <200902050208.50490@zmi.at> In-Reply-To: <200902050208.50490@zmi.at> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Michael Monnerie wrote: > And one last thing: > rsync -aPv /disk1/bigfile /disk2/xxx > That copies at max. 50MB/s, because 2 rsync tasks are started each > taking 50% of 1 CPU - why doesn't the kernel switch the 2nd task to > another CPU? There are 8 cpus in that system - 7 of them idle. Usually in such cases it's because the tasks are piping data to each other in such a way that they can't both run at the same time. In this situation there is no point in moving one to another CPU because they're not executing concurrently anyway.