Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755078Ab1EaDNt (ORCPT ); Mon, 30 May 2011 23:13:49 -0400 Received: from mail-yi0-f46.google.com ([209.85.218.46]:51524 "EHLO mail-yi0-f46.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751407Ab1EaDNs convert rfc822-to-8bit (ORCPT ); Mon, 30 May 2011 23:13:48 -0400 DomainKey-Signature: a=rsa-sha1; c=nofws; d=gmail.com; s=gamma; h=mime-version:in-reply-to:references:date:message-id:subject:from:to :cc:content-type:content-transfer-encoding; b=WWnzLgNXL3PBZp3AzRlDVc2tTQjqsROXEXy98ujTgooT79cv+zBOOAP++tYGSH9dVJ XgTdq5oh5Ot/SWLQOvdumyS4qwsIL7Dv7GgH15dlBcq83tRjiRlraXbJHq3SxUj6q+D/ STlPQIwu7K/7tGRMaVnBvr1mOGc9a0Sa+CHW4= MIME-Version: 1.0 In-Reply-To: <20110531083859.98e4ff43.kamezawa.hiroyu@jp.fujitsu.com> References: <1306774744.4061.5.camel@localhost.localdomain> <20110531083859.98e4ff43.kamezawa.hiroyu@jp.fujitsu.com> Date: Tue, 31 May 2011 09:13:47 +0600 Message-ID: Subject: Re: [PATCH] mm, vmstat: Use cond_resched only when !CONFIG_PREEMPT From: Rakib Mullick To: KAMEZAWA Hiroyuki Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org, akpm@linux-foundation.org, Christoph Lameter , Mel Gorman , KOSAKI Motohiro Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 8BIT Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1839 Lines: 54 On Tue, May 31, 2011 at 5:38 AM, KAMEZAWA Hiroyuki wrote: > On Mon, 30 May 2011 22:59:04 +0600 > Rakib Mullick wrote: > >> commit 468fd62ed9 (vmstats: add cond_resched() to refresh_cpu_vm_stats()) added cond_resched() in refresh_cpu_vm_stats. Purpose of that patch was to allow other threads to run in non-preemptive case. This patch, makes sure that cond_resched() gets called when !CONFIG_PREEMPT is set. In a preemptiable kernel we don't need to call cond_resched(). >> >> Signed-off-by: Rakib Mullick > > Hmm, what benefit do we get by adding this extra #ifdef in the code directly ? > Other cond_resched() callers are not guilty in !CONFIG_PREEMPT ? > Well, in preemptible kernel this context will get preempted if requires, so we don't need cond_resched(). If you checkout the git log of the mentioned commit, you'll find the explanation. It says: "Adding a cond_resched() to allow other threads to run in the non-preemptive case." So, let cond_resched() be in non-preemptive case. Thanks, Rakib > Thanks, > -Kame > >> --- >> >> diff --git a/mm/vmstat.c b/mm/vmstat.c >> index 20c18b7..72cf857 100644 >> --- a/mm/vmstat.c >> +++ b/mm/vmstat.c >> @@ -461,7 +461,11 @@ void refresh_cpu_vm_stats(int cpu) >> ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? p->expire = 3; >> ?#endif >> ? ? ? ? ? ? ? ? ? ? ? } >> + >> +#ifndef CONFIG_PREEMPT >> ? ? ? ? ? ? ? cond_resched(); >> +#endif >> + >> ?#ifdef CONFIG_NUMA >> ? ? ? ? ? ? ? /* >> ? ? ? ? ? ? ? ?* Deal with draining the remote pageset of this >> >> > > -- 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/