From: Jamie Lokier <jamie@shareable.org>
To: Richard Kennedy <richard@rsk.demon.co.uk>
Cc: Jens Axboe <jens.axboe@oracle.com>,
linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org,
chris.mason@oracle.com, david@fromorbit.com, hch@infradead.org,
tytso@mit.edu, akpm@linux-foundation.org, jack@suse.cz
Subject: Re: [PATCH 8/8] vm: Add an tuning knob for vm.max_writeback_mb
Date: Sat, 5 Sep 2009 14:26:53 +0100 [thread overview]
Message-ID: <20090905132653.GH24516@shareable.org> (raw)
In-Reply-To: <4AA13232.5000309@rsk.demon.co.uk>
Richard Kennedy wrote:
> I've been testing this & it works pretty well here, but setting
> max_writeback_mb to 128 seems much too large for normal desktop machines.
>
> Because it is so large the background writes don't stop when they get
> down to the background threshold, but just keep on writing.
> background_threshold on my machine is only about 300Mb so it can
> undershoot by quite a bit. This could impact random write workloads
> significantly.
If that's true, would it be even worse for embedded devices with, say,
just 32MB RAM? It sounds like writeback undershoot might be rather
extreme in that case.
Also on this topic, should max_writeback be smaller for slow disks? I
have a small device here with a hard disk that can only be written at
2-10MB/s due to limitations of the built-in IDE controller.
I know that's unusual, but it shows there is quite a wide range of
speeds at which disks can be written, even just counting hard disks.
-- Jamie
next prev parent reply other threads:[~2009-09-05 13:27 UTC|newest]
Thread overview: 68+ messages / expand[flat|nested] mbox.gz Atom feed top
2009-09-04 7:46 [PATCH 0/8] Per-bdi writeback flusher threads v18 Jens Axboe
2009-09-04 7:46 ` [PATCH 1/8] writeback: get rid of generic_sync_sb_inodes() export Jens Axboe
2009-09-04 8:28 ` Jan Kara
2009-09-04 11:59 ` Jens Axboe
2009-09-04 7:46 ` [PATCH 2/8] writeback: move dirty inodes from super_block to backing_dev_info Jens Axboe
2009-09-04 7:46 ` [PATCH 3/8] writeback: switch to per-bdi threads for flushing data Jens Axboe
2009-09-04 10:54 ` Jan Kara
2009-09-04 11:58 ` Jens Axboe
2009-09-04 12:04 ` [PATCH 3/8] writeback: switch to per-bdi threads for flushing data v2 Jens Axboe
2009-09-04 12:06 ` Jens Axboe
2009-09-07 18:36 ` Jan Kara
2009-09-07 18:45 ` Jens Axboe
2009-09-07 19:45 ` Jan Kara
2009-09-07 19:50 ` Jens Axboe
2009-09-04 7:46 ` [PATCH 4/8] writeback: get rid of pdflush completely Jens Axboe
2009-09-04 7:46 ` [PATCH 5/8] writeback: add some debug inode list counters to bdi stats Jens Axboe
2009-09-04 7:46 ` [PATCH 6/8] writeback: add name to backing_dev_info Jens Axboe
2009-09-04 7:46 ` [PATCH 7/8] writeback: check for registered bdi in flusher add and inode dirty Jens Axboe
2009-09-04 7:46 ` [PATCH 8/8] vm: Add an tuning knob for vm.max_writeback_mb Jens Axboe
2009-09-04 15:28 ` Richard Kennedy
2009-09-05 13:26 ` Jamie Lokier [this message]
2009-09-05 16:18 ` Richard Kennedy
2009-09-05 16:46 ` Theodore Tso
2009-09-07 19:09 ` Jan Kara
-- strict thread matches above, loose matches on Subject: below --
2009-09-08 9:23 [PATCH 0/8] Per-bdi writeback flusher threads v19 Jens Axboe
2009-09-08 9:23 ` [PATCH 8/8] vm: Add an tuning knob for vm.max_writeback_mb Jens Axboe
2009-09-08 10:37 ` Artem Bityutskiy
2009-09-08 16:06 ` Peter Zijlstra
2009-09-08 16:29 ` Chris Mason
2009-09-08 16:56 ` Peter Zijlstra
2009-09-08 17:28 ` Chris Mason
2009-09-08 17:46 ` Peter Zijlstra
2009-09-08 17:55 ` Peter Zijlstra
2009-09-08 18:32 ` Peter Zijlstra
2009-09-09 14:23 ` Jan Kara
2009-09-09 14:37 ` Wu Fengguang
2009-09-10 15:49 ` Peter Zijlstra
2009-09-14 11:17 ` Jan Kara
2009-09-24 8:33 ` Wu Fengguang
2009-09-24 15:38 ` Peter Zijlstra
2009-09-25 1:33 ` Wu Fengguang
2009-09-29 17:35 ` Jan Kara
2009-09-30 1:24 ` Wu Fengguang
2009-09-30 11:55 ` Jan Kara
2009-09-30 12:10 ` Jens Axboe
2009-10-01 15:17 ` Wu Fengguang
2009-10-01 13:36 ` Wu Fengguang
2009-10-01 14:22 ` Jan Kara
2009-10-01 14:54 ` Wu Fengguang
2009-10-01 21:35 ` Jan Kara
2009-10-02 2:25 ` Wu Fengguang
2009-10-02 9:54 ` Jan Kara
2009-10-02 10:34 ` Wu Fengguang
2009-09-08 18:35 ` Chris Mason
2009-09-08 17:57 ` Chris Mason
2009-09-08 18:28 ` Peter Zijlstra
2009-09-09 1:53 ` Dave Chinner
2009-09-09 3:52 ` Wu Fengguang
2009-09-08 18:06 ` Theodore Tso
[not found] ` <20090908181937.GA11545@infradead.org>
2009-09-08 19:34 ` Theodore Tso
2009-09-09 9:29 ` Wu Fengguang
2009-09-09 12:28 ` Christoph Hellwig
2009-09-09 12:32 ` Wu Fengguang
2009-09-09 12:36 ` Artem Bityutskiy
2009-09-09 12:37 ` Jens Axboe
2009-09-09 12:43 ` Christoph Hellwig
2009-09-09 12:44 ` Jens Axboe
2009-09-09 12:51 ` Christoph Hellwig
2009-09-09 12:57 ` Wu Fengguang
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