Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1757918Ab1EaF6F (ORCPT ); Tue, 31 May 2011 01:58:05 -0400 Received: from mail-pw0-f46.google.com ([209.85.160.46]:58582 "EHLO mail-pw0-f46.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751153Ab1EaF6E (ORCPT ); Tue, 31 May 2011 01:58:04 -0400 DomainKey-Signature: a=rsa-sha1; c=nofws; d=gmail.com; s=gamma; h=date:from:to:cc:subject:message-id:references:mime-version :content-type:content-disposition:in-reply-to:user-agent; b=YBWgW53bXvmQ5p8yu2opP/OfBJekQxYE9skJYTVQ69WBwSonFEhC7vurxziokSdGY7 QbsLt+CwrX3fbgV28Hx8exNODue5+wFhDsryvOTVVfVUzmI2FIamRlTB0d4sseR52Fyv l5TuDrCPy03urS4gWH1iOADX+zxjnIo2j0oAA= Date: Tue, 31 May 2011 14:57:57 +0900 From: Minchan Kim To: Rakib Mullick Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org, akpm@linux-foundation.org, Christoph Lameter , KAMEZAWA Hiroyuki , Mel Gorman , KOSAKI Motohiro Subject: Re: [PATCH] mm, vmstat: Use cond_resched only when !CONFIG_PREEMPT Message-ID: <20110531055756.GA2829@barrios-laptop> References: <1306774744.4061.5.camel@localhost.localdomain> <20110531055528.GB1519@barrios-laptop> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20110531055528.GB1519@barrios-laptop> User-Agent: Mutt/1.5.20 (2009-06-14) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1253 Lines: 26 On Tue, May 31, 2011 at 02:55:28PM +0900, Minchan Kim wrote: > On Mon, May 30, 2011 at 10:59:04PM +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 > > Let me ask questions. > > 1. What's bad if we call cond_resched on CONFIG_PREEMPT? > Is refresh_cpu_vm_stats a hot path? > 2. There is no help to call explicit scheduling point on CONFIG_PREEMPTION? > > We used cond_resched without any ifdef/endif of CONFIG_PREEMPT. > In addtion, cond_resched includes __might_sleep which is debugging help for lock. > So I hope let it be if you have a big concern. typo ^^ unless -- Kind regards Minchan Kim -- 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/