linux-kernel - Re: Many open/close on same files yeilds "No such file or directory".

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Message-ID: <20080512060015.GB31262@fieldses.org>
Date:	Mon, 12 May 2008 02:00:15 -0400
From:	"J. Bruce Fields" <bfields@...ldses.org>
To:	Neil Brown <neilb@...e.de>
Cc:	Jesper Krogh <jesper@...gh.cc>,
	Andrew Morton <akpm@...ux-foundation.org>,
	linux-kernel@...r.kernel.org, linux-nfs@...r.kernel.org
Subject: Re: Many open/close on same files yeilds "No such file or
	directory".

On Mon, May 12, 2008 at 11:53:57AM +1000, Neil Brown wrote:
> On Friday May 9, jesper@...gh.cc wrote:
> > 
> > When I disabled the NFS-server and rand my "real-world" program on a
> > single processor (make -j 1). It ran through fine. It basically
> > gets around 20 million chunks out of differnet file and assemble the
> > chuncks in a few other files. This processes more or less 5 individual
> > sections, so make can run effectively with a concurrency of 5.
> 
> (For linux-nfs readers: the problem is that repeatedly opening a given
>  file sometimes returns a ENOENT - http://lkml.org/lkml/2008/5/9/15).
> 
> The mention of an NFS-server made my ears prick up...
> 
> Do I understand correctly that the problem only occurs when you have
> 48 clients hammering away at the filesystem in question?
> 
> Could the clients be accessing the same file that you are experiencing
> problems with?  Or one of the directories in the path (if so, how
> deep).
> 
> How many different files to these 20 million chunks come from?  And
> how does that number compare with the first number from
>    grep dentry /proc/slabinfo
> ??
> 
> The NFS server does some slighty strange things with the dcache if the
> object being access is not in the cache.
> 
> Also, can get a few instances of 
>    grep '^fh' /proc/nfs/rpc/nfsd

I think you meant /proc/net/rpc/nfsd.

--b.

> 
> while things are going strange.  The numbers are:
>  *	fh <stale> <total-lookups> <anonlookups> <dir-not-in-dcache> <nondir-not-in-dcache>
> 
> That will show us if it is looking for things that aren't in the
> dcache.
> 
> Finally, if the filesystem export with "subtree_check" or
> "nosubtree_check"?
> Does it make a difference if you switch the setting of this flag and
> re-export?
> 
> NeilBrown
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