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From: Michal Hocko <mhocko@kernel.org>
To: Arnd Bergmann <arnd@arndb.de>
Cc: Russell King - ARM Linux admin <linux@armlinux.org.uk>,
	Nishanth Menon <nm@ti.com>,
	Santosh Shilimkar <santosh.shilimkar@oracle.com>,
	Tero Kristo <t-kristo@ti.com>,
	Linux ARM <linux-arm-kernel@lists.infradead.org>,
	Rik van Riel <riel@surriel.com>,
	Catalin Marinas <catalin.marinas@arm.com>,
	Santosh Shilimkar <ssantosh@kernel.org>,
	Dave Chinner <david@fromorbit.com>,
	Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
	Linux-MM <linux-mm@kvack.org>, Yafang Shao <laoar.shao@gmail.com>,
	Al Viro <viro@zeniv.linux.org.uk>,
	Johannes Weiner <hannes@cmpxchg.org>,
	linux-fsdevel <linux-fsdevel@vger.kernel.org>,
	kernel-team@fb.com, Kishon Vijay Abraham I <kishon@ti.com>,
	Linus Torvalds <torvalds@linux-foundation.org>,
	Andrew Morton <akpm@linux-foundation.org>,
	Roman Gushchin <guro@fb.com>
Subject: Re: [PATCH] vfs: keep inodes with page cache off the inode shrinker LRU
Date: Tue, 10 Mar 2020 10:16:37 +0100
Message-ID: <20200310091637.GC8447@dhcp22.suse.cz> (raw)
In-Reply-To: <CAK8P3a1HEhwie1uUObQMJyGcs_WSwz4Gj81tAWXZX4d2ff77XA@mail.gmail.com>

I am worried this went quite tangent to the original patch under
discussion here, but let me clarify at least one point.

On Mon 09-03-20 16:04:54, Arnd Bergmann wrote:
> On Mon, Mar 9, 2020 at 3:05 PM Russell King - ARM Linux admin
[...]
> > What happened to requests for memory from highmem being able to be
> > sourced from lowmem if highmem wasn't available?  That used to be
> > standard kernel behaviour.
> 
> AFAICT this is how it's supposed to work, but for some reason it
> doesn't always. I don't know the details, but have heard of recent
> complaints about it. I don't think it's the actual get_free_pages
> failing, but rather some heuristic looking at the number of free pages.

This is indeed the case. There are low memory reserves which are not
allowed for requests which can be satisfied from higher zones. This is
the case for many many years. Just have a look at lowmem_reserve and
their usage in __zone_watermark_ok. The layout of the reserves can be
configured by /proc/sys/vm/lowmem_reserve_ratio.

HTH
-- 
Michal Hocko
SUSE Labs

  reply index

Thread overview: 58+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-02-11 17:55 Johannes Weiner
2020-02-11 18:20 ` Johannes Weiner
2020-02-11 19:05 ` Rik van Riel
2020-02-11 19:31   ` Johannes Weiner
2020-02-11 23:44     ` Andrew Morton
2020-02-12  0:28       ` Linus Torvalds
2020-02-12  0:47         ` Andrew Morton
2020-02-12  1:03           ` Linus Torvalds
2020-02-12  8:50             ` Russell King - ARM Linux admin
2020-02-13  9:50               ` Lucas Stach
2020-02-13 16:52               ` Arnd Bergmann
2020-02-15 11:25                 ` Geert Uytterhoeven
2020-02-15 16:59                   ` Arnd Bergmann
2020-02-16  9:44                     ` Geert Uytterhoeven
2020-02-16 19:54                       ` Chris Paterson
2020-02-16 20:38                         ` Arnd Bergmann
2020-02-20 14:35                           ` Chris Paterson
2020-02-26 18:04                 ` santosh.shilimkar
2020-02-26 21:01                   ` Arnd Bergmann
2020-02-26 21:11                     ` santosh.shilimkar
2020-03-06 20:34                       ` Nishanth Menon
2020-03-07  1:08                         ` santosh.shilimkar
2020-03-08 10:58                         ` Arnd Bergmann
2020-03-08 14:19                           ` Russell King - ARM Linux admin
2020-03-09 13:33                             ` Arnd Bergmann
2020-03-09 14:04                               ` Russell King - ARM Linux admin
2020-03-09 15:04                                 ` Arnd Bergmann
2020-03-10  9:16                                   ` Michal Hocko [this message]
2020-03-09 15:59                           ` Catalin Marinas
2020-03-09 16:09                             ` Russell King - ARM Linux admin
2020-03-09 16:57                               ` Catalin Marinas
2020-03-09 19:46                               ` Arnd Bergmann
2020-03-11 14:29                                 ` Catalin Marinas
2020-03-11 16:59                                   ` Arnd Bergmann
2020-03-11 17:26                                     ` Catalin Marinas
2020-03-11 22:21                                       ` Arnd Bergmann
2020-02-12  3:58         ` Matthew Wilcox
2020-02-12  8:09         ` Michal Hocko
2020-02-17 13:31         ` Pavel Machek
2020-02-12 16:35       ` Johannes Weiner
2020-02-12 18:26         ` Andrew Morton
2020-02-12 18:52           ` Johannes Weiner
2020-02-12 12:25 ` Yafang Shao
2020-02-12 16:42   ` Johannes Weiner
2020-02-13  1:47     ` Yafang Shao
2020-02-13 13:46       ` Johannes Weiner
2020-02-14  2:02         ` Yafang Shao
2020-02-13 18:34 ` [PATCH v2] " Johannes Weiner
2020-02-14 16:53 ` [PATCH] " kbuild test robot
2020-02-14 21:30 ` kbuild test robot
2020-02-14 21:30 ` [PATCH] vfs: fix boolreturn.cocci warnings kbuild test robot
2020-05-12 21:29 ` [PATCH] vfs: keep inodes with page cache off the inode shrinker LRU Johannes Weiner
2020-05-13  1:32   ` Yafang Shao
2020-05-13 13:00     ` Johannes Weiner
2020-05-13 21:15   ` Andrew Morton
2020-05-14 11:27     ` Johannes Weiner
2020-05-14  2:24   ` Andrew Morton
2020-05-14 10:37     ` Johannes Weiner

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