Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752201AbZJXUGg (ORCPT ); Sat, 24 Oct 2009 16:06:36 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1752162AbZJXUGf (ORCPT ); Sat, 24 Oct 2009 16:06:35 -0400 Received: from casper.infradead.org ([85.118.1.10]:35622 "EHLO casper.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751939AbZJXUGe (ORCPT ); Sat, 24 Oct 2009 16:06:34 -0400 Date: Sat, 24 Oct 2009 12:58:53 -0700 From: Arjan van de Ven (by way of Arjan van de Ven ) To: Peter Zijlstra , mingo@elte.hu Message-ID: <20091024125853.35143117@infradead.org> Organization: Intel X-Mailer: Claws Mail 3.7.2 (GTK+ 2.16.6; i586-redhat-linux-gnu) Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Subject: [PATCH 1/3] sched: Enable wake balancing for the SMT/HT domain X-SRS-Rewrite: SMTP reverse-path rewritten from by casper.infradead.org See http://www.infradead.org/rpr.html Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1773 Lines: 45 Subject: sched: Enable wake balancing for the SMT/HT domain From: Arjan van de Ven Logical CPUs that are part of a hyperthreading/SMT set are equivalent in terms of where to execute a task; after all they share pretty much all resources including the L1 cache. This means that if task A wakes up task B, we should really consider all logical CPUs in the SMT/HT set to run task B, not just the CPU that task A is running on; in case task A keeps running, task B now gets to execute with no latency. In the case where task A then immediately goes to wait for a response from task B, nothing is lost due to the aforementioned equivalency. This patch turns on the "balance on wakup" and turns of "affine wakeups" for the SMT/HT scheduler domain to get this lower latency behavior. Signed-off-by: Arjan van de Ven diff --git a/include/linux/topology.h b/include/linux/topology.h index fc0bf3e..3665dc2 100644 --- a/include/linux/topology.h +++ b/include/linux/topology.h @@ -95,8 +95,8 @@ int arch_update_cpu_topology(void); | 1*SD_BALANCE_NEWIDLE \ | 1*SD_BALANCE_EXEC \ | 1*SD_BALANCE_FORK \ - | 0*SD_BALANCE_WAKE \ - | 1*SD_WAKE_AFFINE \ + | 1*SD_BALANCE_WAKE \ + | 0*SD_WAKE_AFFINE \ | 1*SD_SHARE_CPUPOWER \ | 0*SD_POWERSAVINGS_BALANCE \ | 0*SD_SHARE_PKG_RESOURCES \ -- Arjan van de Ven Intel Open Source Technology Centre For development, discussion and tips for power savings, visit http://www.lesswatts.org -- 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/