From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1760265AbZELKox (ORCPT ); Tue, 12 May 2009 06:44:53 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1754572AbZELKon (ORCPT ); Tue, 12 May 2009 06:44:43 -0400 Received: from fgwmail6.fujitsu.co.jp ([192.51.44.36]:46564 "EHLO fgwmail6.fujitsu.co.jp" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754270AbZELKom (ORCPT ); Tue, 12 May 2009 06:44:42 -0400 From: KOSAKI Motohiro To: Ingo Molnar Subject: Re: [tip:sched/core] sched: cpuacct: Use bigger percpu counter batch values for stats counters Cc: kosaki.motohiro@jp.fujitsu.com, Balbir Singh , mingo@redhat.com, hpa@zytor.com, linux-kernel@vger.kernel.org, a.p.zijlstra@chello.nl, schwidefsky@de.ibm.com, balajirrao@gmail.com, dhaval@linux.vnet.ibm.com, bharata@linux.vnet.ibm.com, tglx@linutronix.de, kamezawa.hiroyu@jp.fujitsu.com, linux-tip-commits@vger.kernel.org In-Reply-To: <20090512102939.GB11714@elte.hu> References: <20090512102412.GG6351@balbir.in.ibm.com> <20090512102939.GB11714@elte.hu> Message-Id: <20090512193656.D647.A69D9226@jp.fujitsu.com> MIME-Version: 1.0 Content-Type: text/plain; charset="US-ASCII" Content-Transfer-Encoding: 7bit X-Mailer: Becky! ver. 2.50.07 [ja] Date: Tue, 12 May 2009 19:44:37 +0900 (JST) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org > > * Balbir Singh wrote: > > > * KOSAKI Motohiro [2009-05-12 19:13:42]: > > > > > > > +#ifdef CONFIGCONFIG_SMP > > > > > + cpuacct_batch = jiffies_to_cputime(percpu_counter_batch); > > > > > +#endif > > > > > > > > Slow down and compile patches before sending them out.. please. That > > > > is a basic expectation if you expect it to be merged. > > > > > > Unfortunately, this mistake pass test successfully ;) > > > it because cpuacct_batch=0 works even SMP. > > > > > > > OK, BTW, using an #ifdef right in the middle of a function makes > > the code harder to read, can't we use an inline function to > > abstract out SMP? > > or rather, to make cpuacct_batch have a sane value on UP too. (1? > 0?) umm.. I've reviewed my patch again. but sched_init() already has multiple #ifdef SMP. Thus I don't think cosmetic changing improve readability largely. ------------------------------------ Subject: [PATCH] sched: cpuacct: Use bigger percpu counter batch values for stats counters percpu counters used to accumulate statistics in cpuacct controller use the default batch value [max(2*nr_cpus, 32)] which can be too small for archs that define VIRT_CPU_ACCOUNTING. In such archs, a tick could result in cputime updates in the range of thousands. As a result, cpuacct_update_stats() would end up acquiring the percpu counter spinlock on every tick which is not good for performance. Let those architectures to have a bigger batch threshold so that percpu counter spinlock isn't taken on every tick. This change doesn't affect the archs which don't define VIRT_CPU_ACCOUNTING and they continue to have the default percpu counter batch value. v7: - fix typo and changelog v6: - fix build error when UP v5: - move cpuacct_batch initialization into sched_init() v4: - rewrite patch description (thanks Bharata!) - append read_mostly to cpuacct_batch - cpuacct_batch is initialized by sched_init_debug() v3: - revert using percpu_counter_sum() v2: - use percpu_counter_sum() instead percpu_counter_read() Cc: Balaji Rao Cc: Dhaval Giani Cc: KAMEZAWA Hiroyuki Cc: Peter Zijlstra Cc: Balbir Singh Cc: Ingo Molnar Cc: Martin Schwidefsky Signed-off-by: Bharata B Rao Signed-off-by: KOSAKI Motohiro --- kernel/sched.c | 9 ++++++++- 1 file changed, 8 insertions(+), 1 deletion(-) Index: b/kernel/sched.c =================================================================== --- a/kernel/sched.c 2009-05-12 13:12:59.000000000 +0900 +++ b/kernel/sched.c 2009-05-12 19:04:49.000000000 +0900 @@ -870,6 +870,8 @@ static __read_mostly int scheduler_runni */ int sysctl_sched_rt_runtime = 950000; +static __read_mostly s32 cpuacct_batch; + static inline u64 global_rt_period(void) { return (u64)sysctl_sched_rt_period * NSEC_PER_USEC; @@ -9284,6 +9286,10 @@ void __init sched_init(void) perf_counter_init(); +#ifdef CONFIG_SMP + cpuacct_batch = jiffies_to_cputime(percpu_counter_batch); +#endif + scheduler_running = 1; } @@ -10457,7 +10463,8 @@ static void cpuacct_update_stats(struct ca = task_ca(tsk); do { - percpu_counter_add(&ca->cpustat[idx], val); + __percpu_counter_add(&ca->cpustat[idx], val, cpuacct_batch); + ca = ca->parent; } while (ca); rcu_read_unlock();