Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754117Ab0LJKIr (ORCPT ); Fri, 10 Dec 2010 05:08:47 -0500 Received: from canuck.infradead.org ([134.117.69.58]:58385 "EHLO canuck.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753963Ab0LJKIp convert rfc822-to-8bit (ORCPT ); Fri, 10 Dec 2010 05:08:45 -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> <1291917330.6803.7.camel@twins> <1291920939.6803.38.camel@twins> <1291936593.13513.3.camel@laptop> Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: 8BIT Date: Fri, 10 Dec 2010 11:08:24 +0100 Message-ID: <1291975704.6803.59.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: 956 Lines: 23 On Thu, 2010-12-09 at 15:35 -0800, Venkatesh Pallipadi wrote: > > Just to make sure, update_rq_clock() always gets called on current > CPU. Right? No, specifically not. If that were the case we wouldn't need the cross-cpu synced timestamp. Things like load-balancing and remote-wakeups need to update a remote CPUs clock. > The pending patches I have optimizes > account_system_vtime() to use this_cpu_write and friends. Want to make > sure this change will still keep that optimization relevant. Ah, good point, remote CPUs updating that will mess with the consistency of the per-cpu timestamps due to non atomic updates :/ Bugger.. making them atomics will make it even more expensive. /me goes ponder. -- 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/