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From: Chris Mason <chris.mason@oracle.com>
To: Miklos Szeredi <miklos@szeredi.hu>
Cc: akpm@linux-foundation.org, linux-kernel@vger.kernel.org,
	linux-mm@kvack.org
Subject: Re: dirty balancing deadlock
Date: Tue, 20 Feb 2007 06:30:12 -0500	[thread overview]
Message-ID: <20070220113012.GN6133@think.oraclecorp.com> (raw)
In-Reply-To: <E1HJQeV-0008Kq-00@dorka.pomaz.szeredi.hu>

On Tue, Feb 20, 2007 at 09:47:11AM +0100, Miklos Szeredi wrote:
> > > How about this?
> > > 
> > > Solves the FUSE deadlock, but not the throttle_vm_writeout() one.
> > > I'll try to tackle that one as well.
> > > 
> > > If the per-bdi dirty counter goes below 16, balance_dirty_pages()
> > > returns.
> > > 
> > > Does the constant need to tunable?  If it's too large, then the global
> > > threshold is more easily exceeded.  If it's too small, then in a tight
> > > situation progress will be slower.
> > 
> > Ok, what is supposed to happen here is that filesystems are supposed to
> > be throttled from making more dirty pages when the system is over the
> > threshold.  Even if filesystem A doesn't have much to contribute, and
> > filesystem B is the cause of 99% of the dirty pages, the goal of the
> > threshold is to prevent more dirty data from happening, and filesystem A
> > should block.
> 
> Which is the cause of the current deadlock.  But if we allow
> filesystem A to go into the red just a little, the deadlock is
> avoided, because it can continue to make progress with cleaning the
> dirtyness produced by B.
> 
> The maximum that filesystems can go over the limit will be
> 
>   (16 + epsilon) * number-of-queues

Right, even for thousands of mounted filesystems ~16 pages per FS
effectively pinned is not horrible.

-chris

  reply	other threads:[~2007-02-20 11:31 UTC|newest]

Thread overview: 26+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2007-02-18 18:28 Miklos Szeredi
2007-02-18 20:53 ` Andrew Morton
2007-02-18 21:25   ` Rik van Riel
2007-02-18 22:54     ` Miklos Szeredi
2007-02-18 22:50   ` Miklos Szeredi
2007-02-18 22:59     ` Andrew Morton
2007-02-18 23:22       ` Miklos Szeredi
2007-02-18 23:59         ` Andrew Morton
2007-02-19  0:25           ` Miklos Szeredi
2007-02-19  0:30             ` Miklos Szeredi
2007-02-19  0:45             ` Miklos Szeredi
2007-02-19  0:45             ` Chris Mason
2007-02-19  0:54               ` Miklos Szeredi
2007-02-19  1:01                 ` Chris Mason
2007-02-19  1:14                   ` Miklos Szeredi
2007-02-20  0:16                     ` Chris Mason
2007-02-20  8:53                       ` Miklos Szeredi
2007-02-19 17:11           ` Miklos Szeredi
2007-02-19 23:12             ` Miklos Szeredi
2007-02-20  0:13             ` Chris Mason
2007-02-20  8:47               ` Miklos Szeredi
2007-02-20 11:30                 ` Chris Mason [this message]
2007-02-21 21:36             ` Andrew Morton
2007-02-22  7:42               ` Miklos Szeredi
2007-02-22  7:55                 ` Andrew Morton
2007-02-22  8:02                   ` Miklos Szeredi

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