Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753680AbYLRRyx (ORCPT ); Thu, 18 Dec 2008 12:54:53 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1753112AbYLRRx1 (ORCPT ); Thu, 18 Dec 2008 12:53:27 -0500 Received: from E23SMTP03.au.ibm.com ([202.81.18.172]:57373 "EHLO e23smtp03.au.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753063AbYLRRxZ (ORCPT ); Thu, 18 Dec 2008 12:53:25 -0500 From: Vaidyanathan Srinivasan Subject: [PATCH v7 6/8] sched: activate active load balancing in new idle cpus To: Linux Kernel , Suresh B Siddha , Venkatesh Pallipadi , Peter Zijlstra Cc: Ingo Molnar , Dipankar Sarma , Balbir Singh , Vatsa , Gautham R Shenoy , Andi Kleen , David Collier-Brown , Tim Connors , Max Krasnyansky , Gregory Haskins , Pavel Machek , Andrew Morton , Vaidyanathan Srinivasan Date: Thu, 18 Dec 2008 23:26:36 +0530 Message-ID: <20081218175635.29812.82242.stgit@drishya.in.ibm.com> In-Reply-To: <20081218175313.29812.4781.stgit@drishya.in.ibm.com> References: <20081218175313.29812.4781.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 Active load balancing is a process by which migration thread is woken up on the target CPU in order to pull current running task on another package into this newly idle package. This method is already in use with normal load_balance(), this patch introduces this method to new idle cpus when sched_mc is set to POWERSAVINGS_BALANCE_WAKEUP. This logic provides effective consolidation of short running daemon jobs in a almost idle system The side effect of this patch may be ping-ponging of tasks if the system is moderately utilised. May need to adjust the iterations before triggering. Signed-off-by: Vaidyanathan Srinivasan --- kernel/sched.c | 54 ++++++++++++++++++++++++++++++++++++++++++++++++++++++ 1 files changed, 54 insertions(+), 0 deletions(-) diff --git a/kernel/sched.c b/kernel/sched.c index 3415fa3..f82a7a0 100644 --- a/kernel/sched.c +++ b/kernel/sched.c @@ -3692,10 +3692,64 @@ redo: } if (!ld_moved) { + int active_balance; + schedstat_inc(sd, lb_failed[CPU_NEWLY_IDLE]); if (!sd_idle && sd->flags & SD_SHARE_CPUPOWER && !test_sd_parent(sd, SD_POWERSAVINGS_BALANCE)) return -1; + + if (sched_mc_power_savings < POWERSAVINGS_BALANCE_WAKEUP) + return -1; + + if (sd->nr_balance_failed++ < 2) + return -1; + + /* + * The only task running in a non-idle cpu can be moved to this + * cpu in an attempt to completely freeup the other CPU + * package. The same method used to move task in load_balance() + * have been extended for load_balance_newidle() to speedup + * consolidation at sched_mc=POWERSAVINGS_BALANCE_WAKEUP (2) + * + * The package power saving logic comes from + * find_busiest_group(). If there are no imbalance, then + * f_b_g() will return NULL. However when sched_mc={1,2} then + * f_b_g() will select a group from which a running task may be + * pulled to this cpu in order to make the other package idle. + * If there is no opportunity to make a package idle and if + * there are no imbalance, then f_b_g() will return NULL and no + * action will be taken in load_balance_newidle(). + * + * Under normal task pull operation due to imbalance, there + * will be more than one task in the source run queue and + * move_tasks() will succeed. ld_moved will be true and this + * active balance code will not be triggered. + */ + + /* Lock busiest in correct order while this_rq is held */ + double_lock_balance(this_rq, busiest); + + /* + * don't kick the migration_thread, if the curr + * task on busiest cpu can't be moved to this_cpu + */ + if (!cpu_isset(this_cpu, busiest->curr->cpus_allowed)) { + double_unlock_balance(this_rq, busiest); + all_pinned = 1; + return ld_moved; + } + + if (!busiest->active_balance) { + busiest->active_balance = 1; + busiest->push_cpu = this_cpu; + active_balance = 1; + } + + double_unlock_balance(this_rq, busiest); + if (active_balance) + wake_up_process(busiest->migration_thread); + } else sd->nr_balance_failed = 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/