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Re: [Q] missing unused dentry in prune_dcache()? [message #7851 is a reply to message #7850]

Fri, 27 October 2006 11:50

vaverin
Messages: 708
Registered: September 2005

Senior Member

David,

David Howells wrote:
> Vasily Averin <vvs@sw.ru> wrote:
>> Therefore I believe that my patch is optimal solution.
> I'm not sure that prune_dcache() is particularly optimal.

I means that my patch is optimal for problem in subject. I would like to ask you
to approve it and we will go to next issue.

> If we're looking to
> prune for a specific superblock, it may scan most of the dentry_unused list
> several times, once for each dentry it eliminates.
>
> Imagine the list with a million dentries on it. Imagine further that all the
> dentries you're trying to eliminate are up near the head end: you're going to
> have to scan most of the list several times unnecessarily; if you're asked to
> kill 128 dentries, you might wind up examining on the order of 100,000,000
> dentries, 99% of which you scan 128 times.

I would note that we (Virtuozzo/OpenVZ team) have seen similar issue on praxis.
We have kernel that handles a few dozens Virtual servers, and each of them have
the several isolated filesystems. We have seen that umount (and remount) can
work very slowly, it was cycled inside shrink_dcache_sb() up to several hours
with taken s_umount semaphore.

We are trying to resolve this issue by using per-sb lru list. I'm preparing the
patch for 2.6.19-rc3 right now and going to send it soon.

thank you,
Vasily Averin

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[Message index]

		[Q] missing unused dentry in prune_dcache()? By: vaverin on Wed, 25 October 2006 12:30
		Re: [Q] missing unused dentry in prune_dcache()? By: vaverin on Wed, 25 October 2006 13:58
		Re: [Q] missing unused dentry in prune_dcache()? By: David Howells on Wed, 25 October 2006 14:23
		Re: [Q] missing unused dentry in prune_dcache()? By: vaverin on Thu, 26 October 2006 11:36
		Re: [Q] missing unused dentry in prune_dcache()? By: David Howells on Thu, 26 October 2006 13:25
		Re: [Q] missing unused dentry in prune_dcache()? By: vaverin on Fri, 27 October 2006 08:05
		Re: [Q] missing unused dentry in prune_dcache()? By: David Howells on Fri, 27 October 2006 10:42
		Re: [Q] missing unused dentry in prune_dcache()? By: vaverin on Fri, 27 October 2006 11:50
		Re: [Q] missing unused dentry in prune_dcache()? By: David Howells on Fri, 27 October 2006 12:11
		Re: [Q] missing unused dentry in prune_dcache()? By: vaverin on Fri, 27 October 2006 13:47
		Re: [Q] missing unused dentry in prune_dcache()? By: David Howells on Fri, 27 October 2006 14:29
		Re: [Q] missing unused dentry in prune_dcache()? By: dev on Fri, 27 October 2006 14:34
		[PATCH 2.6.19-rc3] VFS: per-sb dentry lru list By: vaverin on Fri, 27 October 2006 14:05
		Re: [PATCH 2.6.19-rc3] VFS: per-sb dentry lru list By: Andrew Morton on Fri, 27 October 2006 18:06
		Re: [PATCH 2.6.19-rc3] VFS: per-sb dentry lru list By: vaverin on Mon, 30 October 2006 14:24
		Re: [PATCH 2.6.19-rc3] VFS: per-sb dentry lru list By: Eric Dumazet on Mon, 30 October 2006 15:08
		Re: [PATCH 2.6.19-rc3] VFS: per-sb dentry lru list By: dev on Mon, 30 October 2006 15:27
		Re: [PATCH 2.6.19-rc3] VFS: per-sb dentry lru list By: Eric Dumazet on Mon, 30 October 2006 16:09
		Re: [PATCH 2.6.19-rc3] VFS: per-sb dentry lru list By: dev on Mon, 30 October 2006 15:06
		Re: [PATCH 2.6.19-rc3] VFS: per-sb dentry lru list By: David Chinner on Mon, 30 October 2006 04:24
		Re: Re: [PATCH 2.6.19-rc3] VFS: per-sb dentry lru list By: dev on Mon, 30 October 2006 06:22
		Re: Re: [PATCH 2.6.19-rc3] VFS: per-sb dentry lru list By: Neil Brown on Tue, 31 October 2006 04:38
		Re: Re: [PATCH 2.6.19-rc3] VFS: per-sb dentry lru list By: David Howells on Tue, 31 October 2006 10:40
		Re: Re: [PATCH 2.6.19-rc3] VFS: per-sb dentry lru list By: Neil Brown on Wed, 01 November 2006 06:32
		Re: Re: [PATCH 2.6.19-rc3] VFS: per-sb dentry lru list By: vaverin on Wed, 01 November 2006 13:32
		Re: Re: [PATCH 2.6.19-rc3] VFS: per-sb dentry lru list By: Neil Brown on Tue, 14 November 2006 05:44
		Re: [PATCH 2.6.19-rc3] VFS: per-sb dentry lru list By: vaverin on Tue, 14 November 2006 06:12
		Re: [PATCH 2.6.19-rc3] VFS: per-sb dentry lru list By: vaverin on Tue, 31 October 2006 13:08
		Re: Re: [PATCH 2.6.19-rc3] VFS: per-sb dentry lru list By: dev on Wed, 01 November 2006 10:48
		Re: Re: [PATCH 2.6.19-rc3] VFS: per-sb dentry lru list By: Neil Brown on Tue, 14 November 2006 04:51
		Re: Re: [PATCH 2.6.19-rc3] VFS: per-sb dentry lru list By: David Howells on Tue, 14 November 2006 09:29
		[PATCH 2.6.19-rc3] VFS: missing unused dentry in prune_dcache() By: vaverin on Fri, 27 October 2006 13:42
		Re: [PATCH 2.6.19-rc3] VFS: missing unused dentry in prune_dcache() By: David Howells on Fri, 27 October 2006 14:24
		Re: [Q] missing unused dentry in prune_dcache()? By: David Howells on Wed, 25 October 2006 13:51
		Re: [Q] missing unused dentry in prune_dcache()? By: vaverin on Thu, 26 October 2006 11:49
		Re: [Q] missing unused dentry in prune_dcache()? By: David Howells on Thu, 26 October 2006 12:33
		Re: [Q] missing unused dentry in prune_dcache()? By: David Howells on Thu, 26 October 2006 13:23
		Re: [Q] missing unused dentry in prune_dcache()? By: vaverin on Thu, 26 October 2006 13:58
		Re: [Q] missing unused dentry in prune_dcache()? By: David Howells on Thu, 26 October 2006 14:07
		Re: [Q] missing unused dentry in prune_dcache()? By: vaverin on Fri, 27 October 2006 06:32
		Re: [Q] missing unused dentry in prune_dcache()? By: vaverin on Fri, 27 October 2006 06:50
		Re: [Q] missing unused dentry in prune_dcache()? By: David Howells on Fri, 27 October 2006 09:36
		[Q] missing ->d_delete() in shrink_dcache_for_umount()? By: vaverin on Tue, 31 October 2006 13:24
		Re: [Q] missing ->d_delete() in shrink_dcache_for_umount()? By: David Howells on Tue, 31 October 2006 15:06

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