Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752180AbaGaQJV (ORCPT ); Thu, 31 Jul 2014 12:09:21 -0400 Received: from usmamail.tilera.com ([12.216.194.151]:26294 "EHLO USMAMAIL.TILERA.COM" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750854AbaGaQJU (ORCPT ); Thu, 31 Jul 2014 12:09:20 -0400 X-CheckPoint: {53DA6A2F-C-2100090A-C0000000} Message-ID: <53DA6A2F.100@tilera.com> Date: Thu, 31 Jul 2014 12:09:19 -0400 From: Chris Metcalf User-Agent: Mozilla/5.0 (Windows NT 6.1; WOW64; rv:24.0) Gecko/20100101 Thunderbird/24.6.0 MIME-Version: 1.0 To: Michal Hocko , Lai Jiangshan CC: , , Mel Gorman , Tejun Heo , Christoph Lameter , Frederic Weisbecker , Andrea Arcangeli , Rik van Riel , Jianyu Zhan , Johannes Weiner , Khalid Aziz , , Gilad Ben-Yossef Subject: Re: [PATCH] swap: remove the struct cpumask has_work References: <1406777421-12830-3-git-send-email-laijs@cn.fujitsu.com> <20140731115137.GA20244@dhcp22.suse.cz> In-Reply-To: <20140731115137.GA20244@dhcp22.suse.cz> Content-Type: text/plain; charset="ISO-8859-1"; format=flowed Content-Transfer-Encoding: 7bit X-Originating-IP: [10.9.0.23] Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 7/31/2014 7:51 AM, Michal Hocko wrote: > 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. The code uses for_each_cpu with a cpumask to avoid waking cpus that don't need to do work. This is important for the nohz_full type functionality, power efficiency, etc. So, nack for this change. -- Chris Metcalf, Tilera Corp. http://www.tilera.com -- 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/