From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from psmtp.com (na3sys010amx151.postini.com [74.125.245.151]) by kanga.kvack.org (Postfix) with SMTP id 6194B6B004A for ; Mon, 9 Apr 2012 18:29:55 -0400 (EDT) Received: by lagz14 with SMTP id z14so4985358lag.14 for ; Mon, 09 Apr 2012 15:29:53 -0700 (PDT) MIME-Version: 1.0 In-Reply-To: References: <1334000524-23972-1-git-send-email-yinghan@google.com> <20120409125055.c6f6fdf0.akpm@linux-foundation.org> Date: Mon, 9 Apr 2012 15:29:52 -0700 Message-ID: Subject: Re: [PATCH] Revert "mm: vmscan: fix misused nr_reclaimed in shrink_mem_cgroup_zone()" From: Ying Han Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: quoted-printable Sender: owner-linux-mm@kvack.org List-ID: To: Andrew Morton Cc: Rik van Riel , Hillf Danton , Hugh Dickins , linux-mm@kvack.org, Mel Gorman On Mon, Apr 9, 2012 at 2:23 PM, Ying Han wrote: > On Mon, Apr 9, 2012 at 12:50 PM, Andrew Morton > wrote: >> On Mon, =A09 Apr 2012 12:42:04 -0700 >> Ying Han wrote: >> >>> This reverts commit c38446cc65e1f2b3eb8630c53943b94c4f65f670. >>> >>> Before the commit, the code makes senses to me but not after the commit= . The >>> "nr_reclaimed" is the number of pages reclaimed by scanning through the= memcg's >>> lru lists. The "nr_to_reclaim" is the target value for the whole functi= on. For >>> example, we like to early break the reclaim if reclaimed 32 pages under= direct >>> reclaim (not DEF_PRIORITY). >>> >>> After the reverted commit, the target "nr_to_reclaim" is decremented ea= ch time >>> by "nr_reclaimed" but we still use it to compare the "nr_reclaimed". It= just >>> doesn't make sense to me... >>> >>> Signed-off-by: Ying Han >>> --- >>> =A0mm/vmscan.c | =A0 =A07 +------ >>> =A01 files changed, 1 insertions(+), 6 deletions(-) >>> >>> diff --git a/mm/vmscan.c b/mm/vmscan.c >>> index 33c332b..1a51868 100644 >>> --- a/mm/vmscan.c >>> +++ b/mm/vmscan.c >>> @@ -2107,12 +2107,7 @@ restart: >>> =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0* with multiple processes reclaiming pag= es, the total >>> =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0* freeing target can get unreasonably la= rge. >>> =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0*/ >>> - =A0 =A0 =A0 =A0 =A0 =A0 if (nr_reclaimed >=3D nr_to_reclaim) >>> - =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 nr_to_reclaim =3D 0; >>> - =A0 =A0 =A0 =A0 =A0 =A0 else >>> - =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 nr_to_reclaim -=3D nr_reclaim= ed; >>> - >>> - =A0 =A0 =A0 =A0 =A0 =A0 if (!nr_to_reclaim && priority < DEF_PRIORITY= ) >>> + =A0 =A0 =A0 =A0 =A0 =A0 if (nr_reclaimed >=3D nr_to_reclaim && priori= ty < DEF_PRIORITY) >>> =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 break; >>> =A0 =A0 =A0 } >>> =A0 =A0 =A0 blk_finish_plug(&plug); >> >> This code is all within a loop: the "goto restart" thing. =A0We reset >> nr_reclaimed to zero each time around that loop. =A0nr_to_reclaim is (or >> rather, was) constant throughout the entire function. >> >> Comparing nr_reclaimed (whcih is reset each time around the loop) to >> nr_to_reclaim made no sense. >> >> I think the code as it stands is ugly. =A0It would be better to make >> nr_to_reclaim a const and to add another local total_reclaimed, and >> compare that with nr_to_reclaim. > > Ok, I will resend the patch w/ the "total_reclaimed" change. > > --Ying I have the patch ready but I am not sure if that is what we want. If we use total_reclaimed to compare w/ nr_to_reclaim, we end up reducing the amount of work to reclaim before compaction(should_continue_reclaim() is true case). --Ying > > Or just stop resetting nr_reclaimed >> each time around the loop. >> -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Fight unfair telecom internet charges in Canada: sign http://stopthemeter.ca/ Don't email: email@kvack.org