Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756326Ab0LISAx (ORCPT ); Thu, 9 Dec 2010 13:00:53 -0500 Received: from canuck.infradead.org ([134.117.69.58]:47763 "EHLO canuck.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755749Ab0LISAw convert rfc822-to-8bit (ORCPT ); Thu, 9 Dec 2010 13:00:52 -0500 Subject: Re: [BUG] 2.6.37-rc3 massive interactivity regression on ARM From: Peter Zijlstra To: Venkatesh Pallipadi Cc: Russell King - ARM Linux , Mikael Pettersson , Ingo Molnar , linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org, John Stultz In-Reply-To: References: <20101208142814.GE9777@n2100.arm.linux.org.uk> <1291851079-27061-1-git-send-email-venki@google.com> <1291899120.29292.7.camel@twins> Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: 8BIT Date: Thu, 09 Dec 2010 18:55:30 +0100 Message-ID: <1291917330.6803.7.camel@twins> Mime-Version: 1.0 X-Mailer: Evolution 2.30.3 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 796 Lines: 18 On Thu, 2010-12-09 at 09:43 -0800, Venkatesh Pallipadi wrote: > > The same problem will be there with below code, with irq_delta > > delta, clock_task can go backwards which is not good. > + delta -= irq_delta; > + rq->clock_task += delta; > > The reason for this is rq->clock and irqtime updates kind of happen > independently and specifically, if a rq->clock update happens while we > are in a softirq, we may have this case of going backwards on the next > update. But how can irq_delta > delta?, we measure it using the same clock. -- 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/