From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751716Ab3FDXcd (ORCPT ); Tue, 4 Jun 2013 19:32:33 -0400 Received: from lgeamrelo02.lge.com ([156.147.1.126]:45806 "EHLO LGEAMRELO02.lge.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751242Ab3FDXcb (ORCPT ); Tue, 4 Jun 2013 19:32:31 -0400 X-AuditID: 9c93017e-b7bd9ae000006882-db-51ae790dad6f Date: Wed, 5 Jun 2013 08:32:29 +0900 From: Minchan Kim To: Dave Hansen Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org, akpm@linux-foundation.org, mgorman@suse.de, tim.c.chen@linux.intel.com Subject: Re: [v5][PATCH 5/6] mm: vmscan: batch shrink_page_list() locking operations Message-ID: <20130604233229.GB31006@blaptop> References: <20130603200202.7F5FDE07@viggo.jf.intel.com> <20130603200208.6F71D31F@viggo.jf.intel.com> <20130604050103.GC14719@blaptop> <20130604060224.GE14719@blaptop> <51AE07CE.9040304@sr71.net> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <51AE07CE.9040304@sr71.net> User-Agent: Mutt/1.5.21 (2010-09-15) X-Brightmail-Tracker: AAAAAA== Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, Jun 04, 2013 at 08:29:18AM -0700, Dave Hansen wrote: > On 06/03/2013 11:02 PM, Minchan Kim wrote: > >> > Why do we need new lru list instead of using @free_pages? > > I got your point that @free_pages could have freed page by > > put_page_testzero of shrink_page_list and they don't have > > valid mapping so __remove_mapping_batch's mapping_release_page > > would access NULL pointer. > > > > I think it would be better to mention it in comment. :( > > Otherwise, I suggest we can declare another new LIST_HEAD to > > accumulate pages freed by put_page_testzero in shrink_page_list > > so __remove_mapping_batch don't have to declare temporal LRU list > > and can remove unnecessary list_move operation. > > If I respin them again, I'll add a comment. Thanks. it's enough for me. > > I guess we could splice the whole list over at once instead of moving > the pages individually. But, what are we trying to optimize here? > Saving a list_head worth of space on the stack? Never mind. At first, I thought we can simply use @free_pages instead of redundant new LRU list and it's *minor*. That's why I already gave my Reviewed-by. But you woke up my brain so I realized it so I don't have a concern any more about your patch. Thanks. -- Kind regards, Minchan Kim