From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753169AbWKGUcq (ORCPT ); Tue, 7 Nov 2006 15:32:46 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1753185AbWKGUcq (ORCPT ); Tue, 7 Nov 2006 15:32:46 -0500 Received: from mx2.mail.elte.hu ([157.181.151.9]:17349 "EHLO mx2.mail.elte.hu") by vger.kernel.org with ESMTP id S1753169AbWKGUco (ORCPT ); Tue, 7 Nov 2006 15:32:44 -0500 Date: Tue, 7 Nov 2006 21:31:47 +0100 From: Ingo Molnar To: Christoph Lameter Cc: "Siddha, Suresh B" , akpm@osdl.org, mm-commits@vger.kernel.org, nickpiggin@yahoo.com.au, linux-kernel@vger.kernel.org Subject: Re: + sched-use-tasklet-to-call-balancing.patch added to -mm tree Message-ID: <20061107203147.GB4753@elte.hu> References: <200611032205.kA3M5wmJ003178@shell0.pdx.osdl.net> <20061107073248.GB5148@elte.hu> <20061107093112.A3262@unix-os.sc.intel.com> <20061107095049.B3262@unix-os.sc.intel.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.4.2.2i X-ELTE-SpamScore: -2.8 X-ELTE-SpamLevel: X-ELTE-SpamCheck: no X-ELTE-SpamVersion: ELTE 2.0 X-ELTE-SpamCheck-Details: score=-2.8 required=5.9 tests=ALL_TRUSTED,AWL,BAYES_50 autolearn=no SpamAssassin version=3.0.3 -3.3 ALL_TRUSTED Did not pass through any untrusted hosts 0.5 BAYES_50 BODY: Bayesian spam probability is 40 to 60% [score: 0.5000] -0.0 AWL AWL: From: address is in the auto white-list X-ELTE-VirusStatus: clean Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org * Christoph Lameter wrote: > Tasklets are scheduled on the same cpu that triggered the tasklet. > They are just moved to other processors if the processor goes down. So > that aspect is fine. We just need a tasklet struct per cpu. > > User a per cpu tasklet to schedule rebalancing > > Turns out that tasklets have a flag that only allows one instance to > run on all processors. So we need a tasklet structure for each > processor. Per-CPU tasklets are equivalent to softirqs, with extra complexity and overhead ontop of it :-) so please just introduce a rebalance softirq and attach the scheduling rebalance tick to it. But i'd suggest to re-test on the 4096-CPU box, maybe what 'fixed' your workload was the global serialization of the tasklet. With a per-CPU softirq approach we are i think back to the same situation that broke your system before. Ingo