Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1750924AbaBPF0c (ORCPT ); Sun, 16 Feb 2014 00:26:32 -0500 Received: from mail-pb0-f44.google.com ([209.85.160.44]:59159 "EHLO mail-pb0-f44.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750714AbaBPF0a (ORCPT ); Sun, 16 Feb 2014 00:26:30 -0500 Date: Sat, 15 Feb 2014 21:25:39 -0800 (PST) From: Hugh Dickins X-X-Sender: hugh@eggly.anvils To: Weijie Yang cc: Hugh Dickins , Weijie Yang , riel@redhat.com, Mel Gorman , Andrew Morton , Minchan Kim , linux-kernel , Linux-MM Subject: Re: [RFC PATCH] mm/vmscan: remove two un-needed mem_cgroup_page_lruvec() call In-Reply-To: Message-ID: References: <000001cf2ac7$9abf23b0$d03d6b10$%yang@samsung.com> User-Agent: Alpine 2.11 (LSU 23 2013-08-11) MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Sun, 16 Feb 2014, Weijie Yang wrote: > On Sun, Feb 16, 2014 at 12:00 PM, Hugh Dickins wrote: > > On Sun, 16 Feb 2014, Weijie Yang wrote: > > > >> In putback_inactive_pages() and move_active_pages_to_lru(), > >> lruvec is already an input parameter and pages are all from this lruvec, > >> therefore there is no need to call mem_cgroup_page_lruvec() in loop. > >> > >> Signed-off-by: Weijie Yang > > > > Looks plausible but I believe it's incorrect. The lruvec passed in > > is the one we took the pages from, but there's a small but real chance > > that the page has become uncharged meanwhile, and should now be put back > > on the root_mem_cgroup's lruvec instead of the original memcg's lruvec. > > Hi Hugh, > > Thanks for your review. > Frankly speaking, I am not very sure about it, that is why I add a RFC tag here. > So, do we need update the reclaim_stat meanwhile as we change the lruvec? No, it's not worth bothering about, it's only for stats and this is an unlikely case; whereas wrong memcg can be a significant correctness issue. Hugh -- 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/