From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-pa0-f51.google.com (mail-pa0-f51.google.com [209.85.220.51]) by kanga.kvack.org (Postfix) with ESMTP id AB8796B0039 for ; Sun, 15 Jun 2014 20:48:38 -0400 (EDT) Received: by mail-pa0-f51.google.com with SMTP id hz1so688558pad.38 for ; Sun, 15 Jun 2014 17:48:38 -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 ld16si11791105pab.173.2014.06.15.17.48.37 for (version=TLSv1 cipher=ECDHE-RSA-RC4-SHA bits=128/128); Sun, 15 Jun 2014 17:48:37 -0700 (PDT) Received: by mail-pb0-f48.google.com with SMTP id rq2so1791669pbb.35 for ; Sun, 15 Jun 2014 17:48:37 -0700 (PDT) Date: Sun, 15 Jun 2014 17:47:16 -0700 (PDT) From: Hugh Dickins Subject: Re: [PATCH] mm/vmscan.c: avoid recording the original scan targets in shrink_lruvec() In-Reply-To: <1402456897.28433.46.camel@debian> Message-ID: References: <1402320436-22270-1-git-send-email-slaoub@gmail.com> <20140610163338.5b463c5884c4c7e3f1b948e2@linux-foundation.org> <1402456897.28433.46.camel@debian> MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: owner-linux-mm@kvack.org List-ID: To: Chen Yucong Cc: Andrew Morton , mgorman@suse.de, mhocko@suse.cz, hannes@cmpxchg.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org On Wed, 11 Jun 2014, Chen Yucong wrote: > On Tue, 2014-06-10 at 16:33 -0700, Andrew Morton wrote: > > > break; > > > > > > if (nr_file > nr_anon) { > > > - unsigned long scan_target = > > targets[LRU_INACTIVE_ANON] + > > > > > - targets[LRU_ACTIVE_ANON] > > + 1; > > > + nr_to_scan = nr_file - ratio * nr_anon; > > > + percentage = nr[LRU_FILE] * 100 / nr_file; > > > > here, nr_file and nr_anon are derived from the contents of nr[]. But > > nr[] was modified in the for_each_evictable_lru() loop, so its > > contents > > now may differ from what was in targets[]? > > nr_to_scan is used for recording the number of pages that should be > scanned to keep original *ratio*. > > We can assume that the value of (nr_file > nr_anon) is true, nr_to_scan > should be distribute to nr[LRU_ACTIVE_FILE] and nr[LRU_INACTIVE_FILE] in > proportion. > > nr_file = nr[LRU_ACTIVE_FILE] + nr[LRU_INACTIVE_FILE]; > percentage = nr[LRU_FILE] / nr_file; > > Note that in comparison with *old* percentage, the "new" percentage has > the different meaning. It is just used to divide nr_so_scan pages > appropriately. [PATCH] mm-vmscanc-avoid-recording-the-original-scan-targets-in-shrink_lruvec-fix.patch I have not reviewed your logic at all, but soon hit a divide-by-zero crash on mmotm: it needs some such fix as below. Signed-off-by: Hugh Dickins --- mm/vmscan.c | 5 +++-- 1 file changed, 3 insertions(+), 2 deletions(-) --- mmotm/mm/vmscan.c 2014-06-12 17:46:36.632008452 -0700 +++ linux/mm/vmscan.c 2014-06-12 18:55:18.832425713 -0700 @@ -2122,11 +2122,12 @@ static void shrink_lruvec(struct lruvec nr_to_scan = nr_file - ratio * nr_anon; percentage = nr[LRU_FILE] * 100 / nr_file; lru = LRU_BASE; - } else { + } else if (ratio) { nr_to_scan = nr_anon - nr_file / ratio; percentage = nr[LRU_BASE] * 100 / nr_anon; lru = LRU_FILE; - } + } else + break; /* Stop scanning the smaller of the LRU */ nr[lru] = 0; -- 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