From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753448AbYIHNSe (ORCPT ); Mon, 8 Sep 2008 09:18:34 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1751968AbYIHNS0 (ORCPT ); Mon, 8 Sep 2008 09:18:26 -0400 Received: from e28smtp06.in.ibm.com ([59.145.155.6]:52593 "EHLO e28esmtp06.in.ibm.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1751938AbYIHNSZ (ORCPT ); Mon, 8 Sep 2008 09:18:25 -0400 From: Vaidyanathan Srinivasan Subject: [RFC PATCH v2 5/7] sched: nominate preferred wakeup cpu To: Linux Kernel , Suresh B Siddha , Venkatesh Pallipadi Cc: Ingo Molnar , Peter Zijlstra , Dipankar Sarma , Balbir Singh , Vatsa , Gautham R Shenoy , Andi Kleen , David Collier-Brown , Tim Connors , Max Krasnyansky , Vaidyanathan Srinivasan Date: Mon, 08 Sep 2008 18:51:32 +0530 Message-ID: <20080908132132.3221.6102.stgit@drishya.in.ibm.com> In-Reply-To: <20080908131334.3221.61302.stgit@drishya.in.ibm.com> References: <20080908131334.3221.61302.stgit@drishya.in.ibm.com> User-Agent: StGIT/0.14.2 MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org When the system utilisation is low and more cpus are idle, then the process waking up from sleep should prefer to wakeup an idle cpu from semi-idle cpu package (multi core package) rather than a completely idle cpu package which would waste power. Use the sched_mc balance logic in find_busiest_group() to nominate a preferred wakeup cpu. This info can be sored in appropriate sched_domain, but updating this info in all copies of sched_domain is not practical. For now lets try with a global variable. Signed-off-by: Vaidyanathan Srinivasan --- kernel/sched.c | 10 ++++++++++ 1 files changed, 10 insertions(+), 0 deletions(-) diff --git a/kernel/sched.c b/kernel/sched.c index 569fc8d..4ae79f5 100644 --- a/kernel/sched.c +++ b/kernel/sched.c @@ -3380,6 +3380,9 @@ out_balanced: if (this == group_leader && group_leader != group_min) { *imbalance = min_load_per_task; + if (sched_mc_power_savings >= POWERSAVINGS_BALANCE_WAKEUP) + sched_mc_preferred_wakeup_cpu = + first_cpu(group_leader->cpumask); return group_min; } #endif @@ -6911,6 +6914,13 @@ static void sched_domain_node_span(int node, cpumask_t *span) int sched_smt_power_savings = 0, sched_mc_power_savings = 0; /* + * Preferred wake up cpu nominated by sched_mc balance that will be used when + * most cpus are idle in the system indicating overall very low system + * utilisation. Triggered at POWERSAVINGS_BALANCE_WAKEUP (2). + */ +unsigned int sched_mc_preferred_wakeup_cpu; + +/* * SMT sched-domains: */ #ifdef CONFIG_SCHED_SMT