From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-oa0-f52.google.com (mail-oa0-f52.google.com [209.85.219.52]) by kanga.kvack.org (Postfix) with ESMTP id 1B5216B0035 for ; Fri, 6 Jun 2014 09:49:21 -0400 (EDT) Received: by mail-oa0-f52.google.com with SMTP id n16so868602oag.25 for ; Fri, 06 Jun 2014 06:49:20 -0700 (PDT) Received: from mail-pb0-x230.google.com (mail-pb0-x230.google.com [2607:f8b0:400e:c01::230]) by mx.google.com with ESMTPS id eb4si19633502pbb.113.2014.06.06.06.49.20 for (version=TLSv1 cipher=ECDHE-RSA-RC4-SHA bits=128/128); Fri, 06 Jun 2014 06:49:20 -0700 (PDT) Received: by mail-pb0-f48.google.com with SMTP id rr13so2501512pbb.7 for ; Fri, 06 Jun 2014 06:49:20 -0700 (PDT) Message-ID: <1402062463.15497.7.camel@debian> Subject: Re: [PATCH] mm/vmscan.c: avoid scanning the whole targets[*] when scan_balance equals SCAN_FILE/SCAN_ANON From: Chen Yucong Date: Fri, 06 Jun 2014 21:47:43 +0800 In-Reply-To: <20140606131251.GB2878@cmpxchg.org> References: <1402044866-15313-1-git-send-email-slaoub@gmail.com> <20140606131251.GB2878@cmpxchg.org> Content-Type: text/plain; charset="UTF-8" Mime-Version: 1.0 Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org List-ID: To: Johannes Weiner Cc: mgorman@suse.de, mhocko@suse.cz, akpm@linux-foundation.org, linux-mm@kvack.org On Fri, 2014-06-06 at 09:12 -0400, Johannes Weiner wrote: > Hi Chen, > > On Fri, Jun 06, 2014 at 04:54:26PM +0800, Chen Yucong wrote: > > If (scan_balance == SCAN_FILE) is true for shrink_lruvec, then the value of > > targets[LRU_INACTIVE_ANON] and targets[LRU_ACTIVE_ANON] will be zero. As a result, > > the value of 'percentage' will also be zero, and the *whole* targets[LRU_INACTIVE_FILE] > > and targets[LRU_ACTIVE_FILE] will be scanned. > > > > For (scan_balance == SCAN_ANON), there is the same conditions stated above. > > > > But via https://lkml.org/lkml/2013/4/10/334, we can find that the kernel does not prefer > > reclaiming too many pages from the other LRU. So before recalculating the other LRU scan > > count based on its original scan targets and the percentage scanning already complete, we > > should need to check whether 'scan_balance' equals SCAN_FILE/SCAN_ANON. > > > > Signed-off-by: Chen Yucong > > --- > > mm/vmscan.c | 3 +++ > > 1 file changed, 3 insertions(+) > > > > diff --git a/mm/vmscan.c b/mm/vmscan.c > > index d51f7e0..ca3f5f1 100644 > > --- a/mm/vmscan.c > > +++ b/mm/vmscan.c > > @@ -2120,6 +2120,9 @@ static void shrink_lruvec(struct lruvec *lruvec, struct scan_control *sc) > > percentage = nr_file * 100 / scan_target; > > } > > > > + if (targets[lru] == 0 && targets[lru + LRU_ACTIVE] == 0) > > + break; > > We have meanwhile included a change that bails out if nr_anon or > nr_file are zero, right before that percentage calculation, that > should cover the scenario you're describing. It's called: > > mm: vmscan: use proportional scanning during direct reclaim and full scan at DEF_PRIORITY Thanks very much for your reply. Indeed, your patch is more comprehensive and perfect. I think I need to update my local git-repository timely. thx! cyc -- 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/ . Don't email: email@kvack.org