Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755359Ab0DOIAU (ORCPT ); Thu, 15 Apr 2010 04:00:20 -0400 Received: from mail-gy0-f174.google.com ([209.85.160.174]:56123 "EHLO mail-gy0-f174.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752362Ab0DOIAR convert rfc822-to-8bit (ORCPT ); Thu, 15 Apr 2010 04:00:17 -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=cGARbjFp9GqdOF4uaa3y5ByoFxicEmHkVP+2zUVW+MZzk9j/ho+vuCXY50LgvVCbwV q7l5bj/yOyuh3yaTl8sE1rJYbmmjdClrYIfigIqXDftrRqfgmN8zw1RhI9cEJBx8xCG1 cQbHvxK5O92eFcZhaiY9EKEjGrjP1Ek+3Yvx8= MIME-Version: 1.0 In-Reply-To: <4BC6BE78.1030503@kernel.org> References: <9918f566ab0259356cded31fd1dd80da6cae0c2b.1271171877.git.minchan.kim@gmail.com> <20100413154820.GC25756@csn.ul.ie> <4BC65237.5080408@kernel.org> <4BC6BE78.1030503@kernel.org> Date: Thu, 15 Apr 2010 17:00:15 +0900 Message-ID: Subject: Re: [PATCH 2/6] change alloc function in pcpu_alloc_pages From: Minchan Kim To: Tejun Heo Cc: Mel Gorman , Andrew Morton , KAMEZAWA Hiroyuki , Bob Liu , linux-kernel@vger.kernel.org, linux-mm@kvack.org, Christoph Lameter Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8BIT Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2037 Lines: 48 On Thu, Apr 15, 2010 at 4:21 PM, Tejun Heo wrote: > Hello, > > On 04/15/2010 10:31 AM, Minchan Kim wrote: >> Hi, Tejun. >>> This being a pretty cold path, I don't really see much benefit in >>> converting it to alloc_pages_node_exact().  It ain't gonna make any >>> difference.  I'd rather stay with the safer / boring one unless >>> there's a pressing reason to convert. >> >> Actually, It's to weed out not-good API usage as well as some >> performance gain.  But I don't think to need it strongly. >> Okay. Please keep in mind about this and correct it if you confirms >> it in future. :) > > Hmm... if most users are converting over to alloc_pages_node_exact(), > I think it would be better to convert percpu too.  I thought it was a > performance optimization (of rather silly kind too).  So, this is to > weed out -1 node id usage?  Wouldn't it be better to update > alloc_pages_node() such that it whines once per each caller if it's > called with -1 node id and after updating most users convert the > warning into WARN_ON_ONCE()?  Having two variants for this seems > rather extreme to me. Yes. I don't like it. With it, someone who does care about API usage uses alloc_pages_exact_node but someone who don't have a time or careless uses alloc_pages_node. It would make API fragmentation and not good. Maybe we can weed out -1 and make new API which is more clear. * struct page *alloc_pages_any_node(gfp_t gfp_mask, unsigned int order); * struct page *alloc_pages_exact_node(int nid, gfp_mask, unsigned int order); So firstly we have to make sure users who use alloc_pages_node can change alloc_pages_node with alloc_pages_exact_node. After all of it was weed out, I will change alloc_pages_node with alloc_pages_any_node. -- 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/