Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751407AbaGaLvl (ORCPT ); Thu, 31 Jul 2014 07:51:41 -0400 Received: from cantor2.suse.de ([195.135.220.15]:57876 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750826AbaGaLvk (ORCPT ); Thu, 31 Jul 2014 07:51:40 -0400 Date: Thu, 31 Jul 2014 13:51:37 +0200 From: Michal Hocko To: Lai Jiangshan Cc: linux-kernel@vger.kernel.org, akpm@linux-foundation.org, Chris Metcalf , Mel Gorman , Tejun Heo , Christoph Lameter , Frederic Weisbecker , Andrea Arcangeli , Rik van Riel , Jianyu Zhan , Johannes Weiner , Khalid Aziz , linux-mm@kvack.org Subject: Re: [PATCH] swap: remove the struct cpumask has_work Message-ID: <20140731115137.GA20244@dhcp22.suse.cz> References: <1406777421-12830-3-git-send-email-laijs@cn.fujitsu.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1406777421-12830-3-git-send-email-laijs@cn.fujitsu.com> User-Agent: Mutt/1.5.23 (2014-03-12) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu 31-07-14 11:30:19, Lai Jiangshan wrote: > It is suggested that cpumask_var_t and alloc_cpumask_var() should be used > instead of struct cpumask. But I don't want to add this complicity nor > leave this unwelcome "static struct cpumask has_work;", so I just remove > it and use flush_work() to perform on all online drain_work. flush_work() > performs very quickly on initialized but unused work item, thus we don't > need the struct cpumask has_work for performance. Why? Just because there is general recommendation for using cpumask_var_t rather than cpumask? In this particular case cpumask shouldn't matter much as it is static. Your code will work as well, but I do not see any strong reason to change it just to get rid of cpumask which is not on stack. > CC: akpm@linux-foundation.org > CC: Chris Metcalf > CC: Mel Gorman > CC: Tejun Heo > CC: Christoph Lameter > CC: Frederic Weisbecker > Signed-off-by: Lai Jiangshan > --- > mm/swap.c | 11 ++++------- > 1 files changed, 4 insertions(+), 7 deletions(-) > > diff --git a/mm/swap.c b/mm/swap.c > index 9e8e347..bb524ca 100644 > --- a/mm/swap.c > +++ b/mm/swap.c > @@ -833,27 +833,24 @@ static DEFINE_PER_CPU(struct work_struct, lru_add_drain_work); > void lru_add_drain_all(void) > { > static DEFINE_MUTEX(lock); > - static struct cpumask has_work; > int cpu; > > mutex_lock(&lock); > get_online_cpus(); > - cpumask_clear(&has_work); > > for_each_online_cpu(cpu) { > struct work_struct *work = &per_cpu(lru_add_drain_work, cpu); > > + INIT_WORK(work, lru_add_drain_per_cpu); > + > if (pagevec_count(&per_cpu(lru_add_pvec, cpu)) || > pagevec_count(&per_cpu(lru_rotate_pvecs, cpu)) || > pagevec_count(&per_cpu(lru_deactivate_pvecs, cpu)) || > - need_activate_page_drain(cpu)) { > - INIT_WORK(work, lru_add_drain_per_cpu); > + need_activate_page_drain(cpu)) > schedule_work_on(cpu, work); > - cpumask_set_cpu(cpu, &has_work); > - } > } > > - for_each_cpu(cpu, &has_work) > + for_each_online_cpu(cpu) > flush_work(&per_cpu(lru_add_drain_work, cpu)); > > put_online_cpus(); > -- > 1.7.4.4 > > -- > 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/ -- Michal Hocko SUSE Labs -- 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/