From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752857Ab0AaS16 (ORCPT ); Sun, 31 Jan 2010 13:27:58 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1752201Ab0AaS15 (ORCPT ); Sun, 31 Jan 2010 13:27:57 -0500 Received: from casper.infradead.org ([85.118.1.10]:50456 "EHLO casper.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751228Ab0AaS15 (ORCPT ); Sun, 31 Jan 2010 13:27:57 -0500 Date: Sun, 31 Jan 2010 10:28:46 -0800 From: Arjan van de Ven To: Shawn Bohrer Cc: linux-kernel@vger.kernel.org, Ingo Molnar , Peter Zijlstra Subject: Re: High scheduler wake up times Message-ID: <20100131102846.4d1e18aa@infradead.org> In-Reply-To: <20100131034718.GE27390@mediacenter.gateway.2wire.net> References: <20100130234551.GA27390@mediacenter.gateway.2wire.net> <20100130161114.07278221@infradead.org> <20100131003549.GC27390@mediacenter.gateway.2wire.net> <20100130164716.230dfe31@infradead.org> <20100131034718.GE27390@mediacenter.gateway.2wire.net> Organization: Intel X-Mailer: Claws Mail 3.7.3 (GTK+ 2.16.6; i586-redhat-linux-gnu) Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit X-SRS-Rewrite: SMTP reverse-path rewritten from by casper.infradead.org See http://www.infradead.org/rpr.html Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Sat, 30 Jan 2010 21:47:18 -0600 Shawn Bohrer wrote: > > Of course that patch makes my situation worse, which was my point. We > are depending on the _current_ epoll_wait() implementation which calls > schedule_timeout(1). > You do agree that the current epoll_wait() > implementation sleeps less than 1 msec with HZ == 1000 correct? I agree with your hypothesis, but I wouldn't call the behavior correct ;-) First of all, jiffies based timeouts are supposed to round *up*, not down, and second.. it should really be just 1 msec. > With the old kernel I can run 500 of these processes, and I'm hoping > that I'm simply missing the knob I need to tweak to achieve similar > performance on a recent kernel. can you run powertop during your workload? maybe you're getting hit by some C state exit latencies tilting the rounding over the top just too many times... -- Arjan van de Ven Intel Open Source Technology Centre For development, discussion and tips for power savings, visit http://www.lesswatts.org