Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1762147AbXK2Lue (ORCPT ); Thu, 29 Nov 2007 06:50:34 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1755355AbXK2LuZ (ORCPT ); Thu, 29 Nov 2007 06:50:25 -0500 Received: from mx2.mail.elte.hu ([157.181.151.9]:60744 "EHLO mx2.mail.elte.hu" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754320AbXK2LuY (ORCPT ); Thu, 29 Nov 2007 06:50:24 -0500 Date: Thu, 29 Nov 2007 12:50:11 +0100 From: Ingo Molnar To: Miklos Szeredi Cc: jdike@addtoit.com, user-mode-linux-devel@lists.sourceforge.net, linux-kernel@vger.kernel.org Subject: Re: scheduling anomaly on uml (was: -rt doesn't compile for UML) Message-ID: <20071129115011.GA30208@elte.hu> References: <20071128150637.GA5518@c2.user-mode-linux.org> <20071128182935.GA8048@c2.user-mode-linux.org> <20071129105744.GI10577@elte.hu> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.5.17 (2007-11-01) X-ELTE-VirusStatus: clean X-ELTE-SpamScore: -1.5 X-ELTE-SpamLevel: X-ELTE-SpamCheck: no X-ELTE-SpamVersion: ELTE 2.0 X-ELTE-SpamCheck-Details: score=-1.5 required=5.9 tests=BAYES_00 autolearn=no SpamAssassin version=3.2.3 -1.5 BAYES_00 BODY: Bayesian spam probability is 0 to 1% [score: 0.0000] Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1127 Lines: 29 * Miklos Szeredi wrote: > > how come UML idled for 30 msecs here, while the workload was > > supposed to be CPU-bound? It's not IO bound anywhere, right? No SMP > > artifacts either, right? > > Yes. The UML kernel is UP, and I don't think 'date' or 'bash' want to > do any disk I/O. > > Could disk I/O be blocking the tty? I think UML uses separate threads > for these, but I don't know the details. even if the workload is fully CPU bound externally - internally a request to the external (CPU-bound) thread will look like an asynchonous request - so small amounts of idle time can be within UML, legitimately. (for the amount of time it takes for the external thread to service the request) 30 msecs already sounds a bit excessive (this is on your T60 with Core2Duo, right?), and 1-2 seconds noticeable latency is definitely excessive. Ingo - 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/