From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-qt1-f200.google.com (mail-qt1-f200.google.com [209.85.160.200]) by kanga.kvack.org (Postfix) with ESMTP id EDDCD6B0322 for ; Fri, 26 Oct 2018 11:58:52 -0400 (EDT) Received: by mail-qt1-f200.google.com with SMTP id j63-v6so1488303qte.13 for ; Fri, 26 Oct 2018 08:58:52 -0700 (PDT) Received: from mx0b-00082601.pphosted.com (mx0b-00082601.pphosted.com. [67.231.153.30]) by mx.google.com with ESMTPS id b7-v6si688506qtt.31.2018.10.26.08.58.52 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Fri, 26 Oct 2018 08:58:52 -0700 (PDT) From: Roman Gushchin Subject: Re: [RFC PATCH] mm: don't reclaim inodes with many attached pages Date: Fri, 26 Oct 2018 15:58:15 +0000 Message-ID: <20181026155812.GB6019@tower.DHCP.thefacebook.com> References: <20181023164302.20436-1-guro@fb.com> <20181026085735.GZ18839@dhcp22.suse.cz> In-Reply-To: <20181026085735.GZ18839@dhcp22.suse.cz> Content-Language: en-US Content-Type: text/plain; charset="us-ascii" Content-ID: Content-Transfer-Encoding: quoted-printable MIME-Version: 1.0 Sender: owner-linux-mm@kvack.org List-ID: To: Michal Hocko Cc: "linux-mm@kvack.org" , "linux-kernel@vger.kernel.org" , Kernel Team , Rik van Riel , Randy Dunlap , Andrew Morton , "dairinin@gmail.com" On Fri, Oct 26, 2018 at 10:57:35AM +0200, Michal Hocko wrote: > Spock doesn't seem to be cced here - fixed now >=20 > On Tue 23-10-18 16:43:29, Roman Gushchin wrote: > > Spock reported that the commit 172b06c32b94 ("mm: slowly shrink slabs > > with a relatively small number of objects") leads to a regression on > > his setup: periodically the majority of the pagecache is evicted > > without an obvious reason, while before the change the amount of free > > memory was balancing around the watermark. > >=20 > > The reason behind is that the mentioned above change created some > > minimal background pressure on the inode cache. The problem is that > > if an inode is considered to be reclaimed, all belonging pagecache > > page are stripped, no matter how many of them are there. So, if a huge > > multi-gigabyte file is cached in the memory, and the goal is to > > reclaim only few slab objects (unused inodes), we still can eventually > > evict all gigabytes of the pagecache at once. > >=20 > > The workload described by Spock has few large non-mapped files in the > > pagecache, so it's especially noticeable. > >=20 > > To solve the problem let's postpone the reclaim of inodes, which have > > more than 1 attached page. Let's wait until the pagecache pages will > > be evicted naturally by scanning the corresponding LRU lists, and only > > then reclaim the inode structure. >=20 > Has this actually fixed/worked around the issue? >=20 > > Reported-by: Spock > > Signed-off-by: Roman Gushchin > > Cc: Michal Hocko > > Cc: Rik van Riel > > Cc: Randy Dunlap > > Cc: Andrew Morton > > --- > > fs/inode.c | 7 +++++-- > > 1 file changed, 5 insertions(+), 2 deletions(-) > >=20 > > diff --git a/fs/inode.c b/fs/inode.c > > index 73432e64f874..0cd47fe0dbe5 100644 > > --- a/fs/inode.c > > +++ b/fs/inode.c > > @@ -730,8 +730,11 @@ static enum lru_status inode_lru_isolate(struct li= st_head *item, > > return LRU_REMOVED; > > } > > =20 > > - /* recently referenced inodes get one more pass */ > > - if (inode->i_state & I_REFERENCED) { > > + /* > > + * Recently referenced inodes and inodes with many attached pages > > + * get one more pass. > > + */ > > + if (inode->i_state & I_REFERENCED || inode->i_data.nrpages > 1) { >=20 > The comment is just confusing. Did you mean to say s@many@any@ ? No, here many =3D=3D more than 1. I'm happy to fix the comment, if you have any suggestions. Thanks!