From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1765050AbYDOOBh (ORCPT ); Tue, 15 Apr 2008 10:01:37 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1755216AbYDOOB3 (ORCPT ); Tue, 15 Apr 2008 10:01:29 -0400 Received: from netops-testserver-3-out.sgi.com ([192.48.171.28]:58782 "EHLO relay.sgi.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1752883AbYDOOB2 (ORCPT ); Tue, 15 Apr 2008 10:01:28 -0400 Date: Tue, 15 Apr 2008 09:01:27 -0500 From: Dimitri Sivanich To: linux-kernel@vger.kernel.org Cc: Thomas Gleixner , Peter Zijlstra , Ingo Molnar Subject: [PATCH] reduce calls to hrtimer_get_softirq_time Message-ID: <20080415140127.GA32476@sgi.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline User-Agent: Mutt/1.5.13 (2006-08-11) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org It seems that hrtimer_run_queues() is calling hrtimer_get_softirq_time() more often than it needs to. This can cause frequent contention on systems with large numbers of processors/cores. With this patch, hrtimer_run_queues only calls hrtimer_get_softirq_time() if there is a pending timer in one of the hrtimer bases, and only once. This also combines hrtimer_run_queues() and the inline run_hrtimer_queue() into one function. Signed-off-by: Dimitri Sivanich Index: linux/kernel/hrtimer.c =================================================================== --- linux.orig/kernel/hrtimer.c 2008-04-14 14:03:08.000000000 -0500 +++ linux/kernel/hrtimer.c 2008-04-14 15:35:19.594941220 -0500 @@ -1238,51 +1238,52 @@ void hrtimer_run_pending(void) /* * Called from hardirq context every jiffy */ -static inline void run_hrtimer_queue(struct hrtimer_cpu_base *cpu_base, - int index) +void hrtimer_run_queues(void) { struct rb_node *node; - struct hrtimer_clock_base *base = &cpu_base->clock_base[index]; + struct hrtimer_cpu_base *cpu_base = &__get_cpu_var(hrtimer_bases); + struct hrtimer_clock_base *base; + int index; + int gst = 1; - if (!base->first) + if (hrtimer_hres_active()) return; - if (base->get_softirq_time) - base->softirq_time = base->get_softirq_time(); + for (index = 0; index < HRTIMER_MAX_CLOCK_BASES; index++) { + base = &cpu_base->clock_base[index]; - spin_lock(&cpu_base->lock); - - while ((node = base->first)) { - struct hrtimer *timer; - - timer = rb_entry(node, struct hrtimer, node); - if (base->softirq_time.tv64 <= timer->expires.tv64) - break; - - if (timer->cb_mode == HRTIMER_CB_SOFTIRQ) { - __remove_hrtimer(timer, base, HRTIMER_STATE_PENDING, 0); - list_add_tail(&timer->cb_entry, - &base->cpu_base->cb_pending); + if (!base->first) continue; + + if (gst) { + hrtimer_get_softirq_time(cpu_base); + gst = 0; } - __run_hrtimer(timer); - } - spin_unlock(&cpu_base->lock); -} + if (base->get_softirq_time) + base->softirq_time = base->get_softirq_time(); -void hrtimer_run_queues(void) -{ - struct hrtimer_cpu_base *cpu_base = &__get_cpu_var(hrtimer_bases); - int i; + spin_lock(&cpu_base->lock); - if (hrtimer_hres_active()) - return; + while ((node = base->first)) { + struct hrtimer *timer; - hrtimer_get_softirq_time(cpu_base); + timer = rb_entry(node, struct hrtimer, node); + if (base->softirq_time.tv64 <= timer->expires.tv64) + break; + + if (timer->cb_mode == HRTIMER_CB_SOFTIRQ) { + __remove_hrtimer(timer, base, + HRTIMER_STATE_PENDING, 0); + list_add_tail(&timer->cb_entry, + &base->cpu_base->cb_pending); + continue; + } - for (i = 0; i < HRTIMER_MAX_CLOCK_BASES; i++) - run_hrtimer_queue(cpu_base, i); + __run_hrtimer(timer); + } + spin_unlock(&cpu_base->lock); + } } /*