From: Andrew Morton <akpm@linux-foundation.org>
To: Roman Gushchin <guro@fb.com>
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>,
Michal Hocko <mhocko@kernel.org>, Rik van Riel <riel@surriel.com>,
Randy Dunlap <rdunlap@infradead.org>
Subject: Re: [RFC PATCH] mm: don't reclaim inodes with many attached pages
Date: Wed, 24 Oct 2018 15:19:50 -0700 [thread overview]
Message-ID: <20181024151950.36fe2c41957d807756f587ca@linux-foundation.org> (raw)
In-Reply-To: <20181023164302.20436-1-guro@fb.com>
On Tue, 23 Oct 2018 16:43:29 +0000 Roman Gushchin <guro@fb.com> 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.
Is this regression serious enough to warrant fixing 4.19.1?
next prev parent reply other threads:[~2018-10-24 22:19 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 [this message]
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
2018-10-26 17:00 ` Spock
2018-10-26 15:58 ` Roman Gushchin
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