From: Artem Bityutskiy <dedekind1@gmail.com>
To: Jan Kara <jack@suse.cz>
Cc: Ted Tso <tytso@mit.edu>,
Ext4 Mailing List <linux-ext4@vger.kernel.org>,
Linux FS Maling List <linux-fsdevel@vger.kernel.org>,
Linux Kernel Maling List <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH v1 0/9] do not use s_dirt in ext4
Date: Thu, 22 Mar 2012 12:05:47 +0200 [thread overview]
Message-ID: <1332410747.18717.12.camel@sauron.fi.intel.com> (raw)
In-Reply-To: <20120322095342.GC14485@quack.suse.cz>
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On Thu, 2012-03-22 at 10:53 +0100, Jan Kara wrote:
> On Tue 20-03-12 16:41:20, Artem Bityutskiy wrote:
> > This patch-set makes ext4 independent of the VFS superblock management
> > services. Namely, ext4 does not require to register the 'write_super()' VFS
> > call-back.
> >
> > The reason of this exercises is to get rid of the 'sync_supers()' kernel thread
> > which wakes up every 5 seconds (by default) even if all superblocks are clean.
> > This is wasteful from power management POW (unnecessary wake-ups).
> >
> > Note, I tried to optimize 'sync_supers()' instead in 2010, but Al wanted me
> > to get rid of it instead. See https://lkml.org/lkml/2010/6/6/87
> > And I think this is right because many file-systems do not need this, for
> > example btrfs does not use VFS superblock management services at all, so on a
> > btrfs-based system we currently end-up useless periodic wake-ups source.
> >
> > Changes for other file-systems are coming later.
> >
> > The patch-set structure.
> > 1. patches 1,2,3 are independent ext4 cleanups and I ask Ted to merge them as
> > soon/long as they are OK. I sent them also independently in order to get
> > early comments, but did not get so far, so re-sending.
> > 2. patch 4 exports 'dirty_writeback_interval' and it would be very useful to
> > have it merged ASAP to simplify further work
> > 3. patch 5 is also and independent VFS clean-up
> > 4. patches 6-9 actually make ext4 independent on the 'sync_supers()' thread.
> Artem, if you look at places where ext4 sets s_dirt you will notice they
> are rather rare events and all of them actually take care of writing
> superblock themselves (at least if my memory serves well). So ext4
> shouldn't need sync_supers() at all...
Hmm, if there is journal, then ext4 does not initialize the
'->write_super()' VFS call-back and indeed takes care of the SB itself.
Indeed. So 'sync_supers()' wakes up every 5 seconds for nothing.
However, if there is _no_ journal, the 'write_super' is initialized, and
in many places the 's_dirt' flag is set, and thus VFS services seem to
be actively used.
I do not ext4 well enough, but the SB dirtying looks a bit messy, and I
am happy to do some clean-ups, just need a bit more of direction :-)
Thanks!
--
Best Regards,
Artem Bityutskiy
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next prev parent reply other threads:[~2012-03-22 10:03 UTC|newest]
Thread overview: 36+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-03-20 14:41 [PATCH v1 0/9] do not use s_dirt in ext4 Artem Bityutskiy
2012-03-20 14:41 ` [PATCH v1 1/9] ext4: do not mark superblock as dirty unnecessarily Artem Bityutskiy
2012-03-22 9:58 ` Jan Kara
2012-03-20 14:41 ` [PATCH v1 2/9] ext4: write superblock only once on unmount Artem Bityutskiy
2012-03-22 9:59 ` Jan Kara
2012-03-20 14:41 ` [PATCH v1 3/9] ext4: remove useless s_dirt assignment Artem Bityutskiy
2012-03-22 10:02 ` Jan Kara
2012-03-20 14:41 ` [PATCH v1 4/9] mm: export dirty_writeback_interval Artem Bityutskiy
2012-03-20 14:41 ` [PATCH v1 5/9] VFS: remove unused superblock helpers Artem Bityutskiy
2012-03-20 14:41 ` [PATCH v1 6/9] ext4: introduce __ext4_mark_super_dirty Artem Bityutskiy
2012-03-20 14:41 ` [PATCH v1 7/9] ext4: stop using VFS for dirty superblock management Artem Bityutskiy
2012-03-21 8:26 ` Artem Bityutskiy
2012-03-20 14:41 ` [PATCH v1 8/9] ext4: small cleanup in ext4_commit_super Artem Bityutskiy
2012-03-22 10:11 ` Jan Kara
2012-03-20 14:41 ` [PATCH v1 9/9] ext4: introduce own superblock dirty flag Artem Bityutskiy
2012-03-22 9:53 ` [PATCH v1 0/9] do not use s_dirt in ext4 Jan Kara
2012-03-22 10:05 ` Artem Bityutskiy [this message]
2012-03-22 10:33 ` Jan Kara
2012-03-22 11:25 ` Artem Bityutskiy
2012-03-22 13:42 ` Jan Kara
2012-03-22 13:59 ` Artem Bityutskiy
2012-03-27 13:29 ` Artem Bityutskiy
2012-03-27 20:14 ` Jan Kara
2012-03-28 8:44 ` Artem Bityutskiy
2012-03-28 10:15 ` Jan Kara
2012-03-30 15:23 ` Artem Bityutskiy
2012-03-30 15:35 ` Jan Kara
2012-03-30 15:43 ` Artem Bityutskiy
2012-03-31 11:49 ` Jan Kara
2012-04-02 13:46 ` Artem Bityutskiy
2012-03-31 12:25 ` Artem Bityutskiy
2012-03-22 13:35 ` Ted Ts'o
2012-03-22 13:56 ` Artem Bityutskiy
2012-03-22 15:06 ` Ted Ts'o
2012-03-23 8:55 ` Artem Bityutskiy
2012-03-23 14:23 ` Ted Ts'o
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