From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from psmtp.com (na3sys010amx130.postini.com [74.125.245.130]) by kanga.kvack.org (Postfix) with SMTP id 519F06B0044 for ; Mon, 9 Apr 2012 17:23:14 -0400 (EDT) Received: by lbao2 with SMTP id o2so2766566lba.14 for ; Mon, 09 Apr 2012 14:23:12 -0700 (PDT) MIME-Version: 1.0 In-Reply-To: <20120409125055.c6f6fdf0.akpm@linux-foundation.org> References: <1334000524-23972-1-git-send-email-yinghan@google.com> <20120409125055.c6f6fdf0.akpm@linux-foundation.org> Date: Mon, 9 Apr 2012 14:23:11 -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 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 functio= n. 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 eac= h 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 page= s, the total >> =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0* freeing target can get unreasonably lar= ge. >> =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_reclaime= d; >> - >> - =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 && priorit= y < 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 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