From: Arnd Bergmann <arnd@arndb.de>
To: Russell King - ARM Linux admin <linux@armlinux.org.uk>
Cc: 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>,
Michal Hocko <mhocko@suse.com>, 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: Mon, 9 Mar 2020 14:33:26 +0100 [thread overview]
Message-ID: <CAK8P3a2Gz5H_fcNtW0yCCjO1cRNa0nyd568sDYR0nNphu49YqQ@mail.gmail.com> (raw)
In-Reply-To: <20200308141923.GI25745@shell.armlinux.org.uk>
On Sun, Mar 8, 2020 at 3:20 PM Russell King - ARM Linux admin
<linux@armlinux.org.uk> wrote:
> On Sun, Mar 08, 2020 at 11:58:52AM +0100, Arnd Bergmann wrote:
> > On Fri, Mar 6, 2020 at 9:36 PM Nishanth Menon <nm@ti.com> wrote:
> > > On 13:11-20200226, santosh.shilimkar@oracle.com wrote:
>
> > - extend zswap to use all the available high memory for swap space
> > when highmem is disabled.
>
> I don't think that's a good idea. Running debian stable kernels on my
> 8GB laptop, I have problems when leaving firefox running long before
> even half the 16GB of swap gets consumed - the entire machine slows
> down very quickly when it starts swapping more than about 2 or so GB.
> It seems either the kernel has become quite bad at selecting pages to
> evict.
>
> It gets to the point where any git operation has a battle to fight
> for RAM, despite not touching anything else other than git.
>
> The behaviour is much like firefox is locking memory into core, but
> that doesn't seem to be what's actually going on. I've never really
> got to the bottom of it though.
>
> This is with 64-bit kernel and userspace.
I agree there is something going wrong on your machine, but I
don't really see how that relates to my suggestion.
> So, I'd suggest that trading off RAM available through highmem for VM
> space available through zswap is likely a bad idea if you have a
> workload that requires 4GB of RAM on a 32-bit machine.
Aside from every workload being different, I was thinking of
these general observations:
- If we are looking at a future without highmem, then it's better to use
the extra memory for something than not using it. zswap seems like
a reasonable use.
- A lot of embedded systems are configured to have no swap at all,
which can be for good or not-so-good reasons. Having some
swap space available often improves things, even if it comes
out of RAM.
- A particularly important case to optimize for is 2GB of RAM with
LPAE enabled. With CONFIG_VMSPLIT_2G and highmem, this
leads to the paradox -ENOMEM when 256MB of highmem are
full while plenty of lowmem is available. With highmem disabled,
you avoid that at the cost of losing 12% of RAM.
- With 4GB+ of RAM and CONFIG_VMSPLIT_2G or
CONFIG_VMSPLIT_3G, using gigabytes of RAM for swap
space would usually be worse than highmem, but once
we have VMSPLIT_4G_4G, it's the same situation as above
with 6% of RAM used for zswap instead of highmem.
Arnd
next prev parent reply other threads:[~2020-03-09 13:33 UTC|newest]
Thread overview: 58+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-02-11 17:55 [PATCH] vfs: keep inodes with page cache off the inode shrinker LRU 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 [this message]
2020-03-09 14:04 ` Russell King - ARM Linux admin
2020-03-09 15:04 ` Arnd Bergmann
2020-03-10 9:16 ` Michal Hocko
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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