From: "Rafael J. Wysocki" <rjw@sisk.pl>
To: Miklos Szeredi <miklos@szeredi.hu>
Cc: linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org,
Andrew Morton <akpm@osdl.org>,
Nigel Cunningham <ncunningham@linuxmail.org>,
Pavel Machek <pavel@ucw.cz>
Subject: Re: Quadratic behavior of shrink_dcache_parent()
Date: Tue, 21 Nov 2006 00:03:12 +0100 [thread overview]
Message-ID: <200611210003.13417.rjw@sisk.pl> (raw)
In-Reply-To: <E1Gm731-0003Br-00@dorka.pomaz.szeredi.hu>
On Monday, 20 November 2006 12:10, Miklos Szeredi wrote:
> The shrink_dcache_parent() can take a very long time for deep
> directory trees: minutes for depth of 100,000, probably hours for
> depth of 1,000,000.
>
> The reason is that after dropping a leaf, it starts again from the
> root.
Oh, well. So that's the reason why the shrinking of memory in swsusp can
take so much time.
> Filesystems affected include FUSE, NFS, CIFS. Others I haven't
> checked. NFS and to a lesser extent CIFS don't seem to efficiently
> handle lookups within such a deep hierarchy, so they're sort of
> immune.
>
> But with FUSE it's pretty easy to DoS the system.
>
> Limiting the depth to some sane value could work around this problem,
> but that would mean having to traverse subtrees in rename().
>
> Any better ideas?
None, for now. It looks like I need to learn that code ...
Greetings,
Rafael
--
You never change things by fighting the existing reality.
R. Buckminster Fuller
prev parent reply other threads:[~2006-11-20 23:06 UTC|newest]
Thread overview: 2+ messages / expand[flat|nested] mbox.gz Atom feed top
2006-11-20 11:10 Miklos Szeredi
2006-11-20 23:03 ` Rafael J. Wysocki [this message]
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