From: Roman Gushchin <guro@fb.com>
To: Michal Hocko <mhocko@kernel.org>
Cc: "linux-mm@kvack.org" <linux-mm@kvack.org>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
Kernel Team <Kernel-team@fb.com>,
"Rik van Riel" <riel@surriel.com>,
Randy Dunlap <rdunlap@infradead.org>,
Andrew Morton <akpm@linux-foundation.org>,
"dairinin@gmail.com" <dairinin@gmail.com>
Subject: Re: [RFC PATCH] mm: don't reclaim inodes with many attached pages
Date: Fri, 26 Oct 2018 15:56:55 +0000 [thread overview]
Message-ID: <20181026155652.GA7647@tower.DHCP.thefacebook.com> (raw)
In-Reply-To: <20181026085735.GZ18839@dhcp22.suse.cz>
On Fri, Oct 26, 2018 at 10:57:35AM +0200, Michal Hocko wrote:
> Spock doesn't seem to be cced here - fixed now
>
> 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.
> >
> > 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.
> >
> > The workload described by Spock has few large non-mapped files in the
> > pagecache, so it's especially noticeable.
> >
> > 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.
>
> Has this actually fixed/worked around the issue?
Spock wrote this earlier to me directly. I believe I can quote it here:
"Patch applied, looks good so far. System behaves like it was with
pre-4.18.15 kernels.
Also tried to add some user-level tests to the geneic background activity, like
- stat'ing a bunch of files
- streamed read several large files at once on ext4 and XFS
- random reads on the whole collection with a read size of 16K
I will be monitoring while fragmentation stacks up and report back if
something bad happens."
Spock, please let me know if you have any new results.
Thanks!
next prev parent reply other threads:[~2018-10-26 15:57 UTC|newest]
Thread overview: 17+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-10-23 16:43 [RFC PATCH] mm: don't reclaim inodes with many attached pages Roman Gushchin
2018-10-24 22:18 ` Andrew Morton
2018-10-24 23:49 ` Roman Gushchin
2018-10-24 22:19 ` Andrew Morton
2018-10-24 23:51 ` Roman Gushchin
2018-10-25 9:23 ` Michal Hocko
2018-10-25 19:44 ` Andrew Morton
2018-10-25 20:20 ` Sasha Levin
2018-10-25 20:27 ` Matthew Wilcox
2018-10-25 21:44 ` Sasha Levin
2018-10-25 20:32 ` Roman Gushchin
2018-10-26 7:33 ` Michal Hocko
2018-10-26 15:54 ` Roman Gushchin
2018-10-26 8:57 ` Michal Hocko
2018-10-26 15:56 ` Roman Gushchin [this message]
2018-10-26 17:00 ` Spock
2018-10-26 15:58 ` Roman Gushchin
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