From: Marc Lehmann <schmorp@schmorp.de>
To: Filipe Manana <fdmanana@gmail.com>
Cc: linux-btrfs <linux-btrfs@vger.kernel.org>
Subject: Re: cpu bound I/O behaviour in linux 5.4 (possibly others)
Date: Fri, 14 Feb 2020 21:07:00 +0100 [thread overview]
Message-ID: <20200214200659.GA7612@schmorp.de> (raw)
In-Reply-To: <CAL3q7H7SPyXB+5G6+XtgfviJdBQQSYD1YyJZPX6rbWxhes-+qw@mail.gmail.com>
On Fri, Feb 14, 2020 at 12:20:46PM +0000, Filipe Manana <fdmanana@gmail.com> wrote:
> So you can't deduce that the free space cache is being used, and
> despite being the default, it was not mentioned by Marc if he's not
> using already the free space tree (-o space_cache=v2).
Today, during an idle period, I stopped the news process, waited 15
minutes for I/O tand CPU to become mostly idle, and did this:
# mount -noremount,clear_cache,space_cache=v1 /localvol5
# mount -noremount,clear_cache,space_cache=v2 /localvol5
Which, to my surprise, didn't make btrfs complain too much:
[1378546.558533] BTRFS info (device dm-17): force clearing of disk cache
[1378546.558536] BTRFS info (device dm-17): enabling disk space caching
[1378546.558537] BTRFS info (device dm-17): disk space caching is enabled
[1378553.868438] BTRFS info (device dm-17): enabling free space tree
[1378553.868440] BTRFS info (device dm-17): using free space tree
I don't know if this was effective in clearing the cache, but it didn't
change the behaviour - as soon as the new process started writing files
again, it was at 100% cpu.
--
The choice of a Deliantra, the free code+content MORPG
-----==- _GNU_ http://www.deliantra.net
----==-- _ generation
---==---(_)__ __ ____ __ Marc Lehmann
--==---/ / _ \/ // /\ \/ / schmorp@schmorp.de
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next prev parent reply other threads:[~2020-02-14 20:07 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-02-14 11:30 cpu bound I/O behaviour in linux 5.4 (possibly others) Marc Lehmann
2020-02-14 11:57 ` Nikolay Borisov
2020-02-14 12:20 ` Filipe Manana
2020-02-14 20:07 ` Marc Lehmann [this message]
2020-02-14 12:40 ` Marc Lehmann
2020-02-14 12:36 ` Roman Mamedov
2020-02-14 12:45 ` Marc Lehmann
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