Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754254AbZDNEz7 (ORCPT ); Tue, 14 Apr 2009 00:55:59 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1753109AbZDNEzl (ORCPT ); Tue, 14 Apr 2009 00:55:41 -0400 Received: from e28smtp06.in.ibm.com ([59.145.155.6]:56976 "EHLO e28smtp06.in.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752754AbZDNEzk (ORCPT ); Tue, 14 Apr 2009 00:55:40 -0400 From: Gautham R Shenoy Subject: [RFC PATCH 2 2/2] sched: Nominate a power-efficient ilb in select_nohz_balancer() To: "Ingo Molnar" , Peter Zijlstra , "Vaidyanathan Srinivasan" Cc: linux-kernel@vger.kernel.org, "Balbir Singh" , Suresh Siddha , "Andi Kleen" , Randy Dunlap , Gautham R Shenoy Date: Tue, 14 Apr 2009 10:25:35 +0530 Message-ID: <20090414045535.7645.31641.stgit@sofia.in.ibm.com> In-Reply-To: <20090414045356.7645.33369.stgit@sofia.in.ibm.com> References: <20090414045356.7645.33369.stgit@sofia.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 Content-Length: 1676 Lines: 51 The CPU that first goes idle becomes the idle-load-balancer and remains that until either it picks up a task or till all the CPUs of the system goes idle. Optimize this further to allow it to relinquish it's post once all it's siblings in the power-aware sched_domain go idle, thereby allowing the whole package-core to go idle. While relinquising the post, nominate another an idle-load balancer from a semi-idle core/package. Signed-off-by: Gautham R Shenoy --- kernel/sched.c | 18 +++++++++++++++++- 1 files changed, 17 insertions(+), 1 deletions(-) diff --git a/kernel/sched.c b/kernel/sched.c index d702be7..bbf367d 100644 --- a/kernel/sched.c +++ b/kernel/sched.c @@ -4402,8 +4402,24 @@ int select_nohz_load_balancer(int stop_tick) /* make me the ilb owner */ if (atomic_cmpxchg(&nohz.load_balancer, -1, cpu) == -1) return 1; - } else if (atomic_read(&nohz.load_balancer) == cpu) + } else if (atomic_read(&nohz.load_balancer) == cpu) { + int new_ilb; + + if (!(sched_smt_power_savings || + sched_mc_power_savings)) + return 1; + /* + * Check to see if there is a more power-efficient + * ilb. + */ + new_ilb = find_new_ilb(cpu); + if (new_ilb < nr_cpu_ids && new_ilb != cpu) { + atomic_set(&nohz.load_balancer, -1); + resched_cpu(new_ilb); + return 0; + } return 1; + } } else { if (!cpumask_test_cpu(cpu, nohz.cpu_mask)) return 0; -- 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/