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 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 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 [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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