Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932076AbVJ0BYq (ORCPT ); Wed, 26 Oct 2005 21:24:46 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S932619AbVJ0BYq (ORCPT ); Wed, 26 Oct 2005 21:24:46 -0400 Received: from fmr21.intel.com ([143.183.121.13]:5300 "EHLO scsfmr001.sc.intel.com") by vger.kernel.org with ESMTP id S932076AbVJ0BYp (ORCPT ); Wed, 26 Oct 2005 21:24:45 -0400 Message-Id: <200510270124.j9R1OPg27107@unix-os.sc.intel.com> From: "Chen, Kenneth W" To: "'Ingo Molnar'" , "Nick Piggin" , "Andrew Morton" Cc: Subject: better wake-balancing: respin Date: Wed, 26 Oct 2005 18:24:25 -0700 MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit X-Mailer: Microsoft Office Outlook, Build 11.0.6353 Thread-Index: AcXalSsjyf4J9a1rRVG4O3vn7bOx+Q== X-MimeOLE: Produced By Microsoft MimeOLE V6.00.2900.2180 Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1898 Lines: 50 Once upon a time, this patch was in -mm tree (2.6.13-mm1): http://marc.theaimsgroup.com/?l=linux-kernel&m=112265450426975&w=2 It is neither in Linus's official tree, nor it is in -mm anymore. I guess I missed the objection for dropping the patch. I'm bringing up this discussion again. The wake-up path is a lot hotter on numa system running database benchmark. Even on a moderate 8P numa box, __wake_up and try_to_wake_up is showing up as #1 and #4 hottest kernel functions. While on a comparable 4P smp box, these two functions are #5 and #9 respectively. I think situation will be worse on 32P numa box in the wake up path. I don't have any measurement on 32P setup yet, because 8P numa performance sucks at the moment and it is a blocker for us before proceed any bigger setup. Execution profile for 8P numa box [1]: Symbol Clockticks Inst. Retired L3 Misses #1 __wake_up 8.08% 1.88% 4.67% #2 finish_task_switch 7.53% 18.11% 5.82% #3 __make_request 6.87% 2.09% 4.35% #4 try_to_wake_up 5.57% 0.64% 3.10% Execution profile for 4P SMP box [2]: Symbol Clockticks #5 __wake_up 3.57% #9 try_to_wake_up 2.38% My question is: what was the reason this patch is dropped and what can we do to improve wake-up performance? In my opinion, we should simply put the task on the CPU it was previously ran and have rebalance_tick and load_balance_newidle to balance out the load. - Ken [1] 8 processor: 1.6 GHz Itanium2 processor, 9M L3. 256 GB memory [2] 4 processor: 1.6 GHz Itanium2 processor, 9M L3. 128 GB memory - 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/