From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755512Ab3AEIhg (ORCPT ); Sat, 5 Jan 2013 03:37:36 -0500 Received: from mga11.intel.com ([192.55.52.93]:44979 "EHLO mga11.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755331Ab3AEIhP (ORCPT ); Sat, 5 Jan 2013 03:37:15 -0500 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="4.84,415,1355126400"; d="scan'208";a="270210066" From: Alex Shi To: mingo@redhat.com, peterz@infradead.org, tglx@linutronix.de, akpm@linux-foundation.org, arjan@linux.intel.com, bp@alien8.de, pjt@google.com, namhyung@kernel.org, efault@gmx.de Cc: vincent.guittot@linaro.org, gregkh@linuxfoundation.org, preeti@linux.vnet.ibm.com, linux-kernel@vger.kernel.org, alex.shi@intel.com Subject: [PATCH v3 05/22] sched: remove domain iterations in fork/exec/wake Date: Sat, 5 Jan 2013 16:37:34 +0800 Message-Id: <1357375071-11793-6-git-send-email-alex.shi@intel.com> X-Mailer: git-send-email 1.7.12 In-Reply-To: <1357375071-11793-1-git-send-email-alex.shi@intel.com> References: <1357375071-11793-1-git-send-email-alex.shi@intel.com> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Guess the search cpu from bottom to up in domain tree come from commit 3dbd5342074a1e sched: multilevel sbe sbf, the purpose is balancing over tasks on all level domains. This balancing cost much if there has many domain/groups in a large system. And force spreading task among different domains may cause performance issue due to bad locality. If we remove this code, we will get quick fork/exec/wake, plus better balancing among whole system, that also reduce migrations in future load balancing. This patch increases 10+% performance of hackbench on my 4 sockets NHM and SNB machines. Signed-off-by: Alex Shi --- kernel/sched/fair.c | 20 +------------------- 1 file changed, 1 insertion(+), 19 deletions(-) diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c index ecfbf8e..895a3f4 100644 --- a/kernel/sched/fair.c +++ b/kernel/sched/fair.c @@ -3364,15 +3364,9 @@ select_task_rq_fair(struct task_struct *p, int sd_flag, int wake_flags) goto unlock; } - while (sd) { + if (sd) { int load_idx = sd->forkexec_idx; struct sched_group *group; - int weight; - - if (!(sd->flags & sd_flag)) { - sd = sd->child; - continue; - } if (sd_flag & SD_BALANCE_WAKE) load_idx = sd->wake_idx; @@ -3382,18 +3376,6 @@ select_task_rq_fair(struct task_struct *p, int sd_flag, int wake_flags) goto unlock; new_cpu = find_idlest_cpu(group, p, cpu); - - /* Now try balancing at a lower domain level of new_cpu */ - cpu = new_cpu; - weight = sd->span_weight; - sd = NULL; - for_each_domain(cpu, tmp) { - if (weight <= tmp->span_weight) - break; - if (tmp->flags & sd_flag) - sd = tmp; - } - /* while loop will break here if sd == NULL */ } unlock: rcu_read_unlock(); -- 1.7.12