Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752913AbYKGKTH (ORCPT ); Fri, 7 Nov 2008 05:19:07 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1751510AbYKGKSy (ORCPT ); Fri, 7 Nov 2008 05:18:54 -0500 Received: from bombadil.infradead.org ([18.85.46.34]:47109 "EHLO bombadil.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751497AbYKGKSy (ORCPT ); Fri, 7 Nov 2008 05:18:54 -0500 Subject: Re: [PATCH] revert: timers: fix itimer/many thread hang From: Peter Zijlstra To: Christoph Lameter Cc: Ingo Molnar , Frank Mayhar , Doug Chapman , roland@redhat.com, adobriyan@gmail.com, akpm@linux-foundation.org, linux-kernel In-Reply-To: References: <1224694989.8431.23.camel@oberon> <1225132746.14792.13.camel@bobble.smo.corp.google.com> <1225219114.24204.37.camel@oberon> <1225936715.27507.44.camel@bobble.smo.corp.google.com> <1225969420.7803.4366.camel@twins> <1225989102.7803.4749.camel@twins> <20081106214434.GA5999@elte.hu> Content-Type: text/plain Content-Transfer-Encoding: 7bit Date: Fri, 07 Nov 2008 11:19:32 +0100 Message-Id: <1226053172.7803.5832.camel@twins> Mime-Version: 1.0 X-Mailer: Evolution 2.24.1 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1147 Lines: 25 On Thu, 2008-11-06 at 15:53 -0600, Christoph Lameter wrote: > On Thu, 6 Nov 2008, Ingo Molnar wrote: > > > That loop could _perhaps_ be avoided by maintaining the sums from the > > scheduler tick: by just adding the latest delta values for the current > > task to times->*time. Plus at exit time cleaning up the remaining > > delta. That would be a far smaller patch. > > That is a similar scheme to the ZVC (see mm/vmstat.c). Peter: Dont you > have an implementation of a ZVC like scheme for you dirty throttling > patchset that may be useful here? Sure, we can do something similar to that, but mind you, that's an approximation. Approximations work just fine for vmstats and dirty balancing, I'm just not sure its something people appreciate wrt timers :-) The trick is to only update the sum when a per-cpu delta overflows, which means the sum will have an error in the order of cpus*delta/2. -- 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/