From: "Jose R. Santos" <jrsantos@austin.ibm.com>
Subject: Re: dentry/inode cache invalidation when using nfsd filesystem on 2.6
Date: Thu, 23 Oct 2003 07:40:16 -0500
Sender: nfs-admin@lists.sourceforge.net
Message-ID: <20031023124016.GH6172@dbz.austin.ibm.com>
References: <20031021142414.GW1516@dbz.austin.ibm.com> <16279.20926.488909.525633@notabene.cse.unsw.edu.au>
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Cc: Linux NFS Mailing List <nfs@lists.sourceforge.net>
To: Neil Brown <neilb@cse.unsw.edu.au>
In-Reply-To: <16279.20926.488909.525633@notabene.cse.unsw.edu.au> (from neilb@cse.unsw.edu.au on Wed, Oct 22, 2003 at 22:57:50 -0500)
Errors-To: nfs-admin@lists.sourceforge.net

On 10/22/03 22:57:50, Neil Brown wrote:
> 
> The problem is NOT that the inode or dentry caches are being flushed.
> 
> The problem is that the inode and dentry caches
> *for*the*(tiny)*nfsd*filesystem*
> are being flushed, and this requires iterating through each cache under a
> spinlock, and this can take a while.

I saw some weirdness that led me to believe kernel was invalidating more than  
it should.  I will investigate further to make sure this is not happening.
 
> Basically, "mount" and "unmount" are slow operations.

The only problem is that it seems to get worst as the memory of the system get  
bigger, but I'll agree with you on the SEP. So, I'll just drop it. :)
 
> As you note, "unmount" can be avoided by mounting the nfsd filesystem
> somewhere.  I recommend /proc/fs/nfsd.
> The "mount" can be avoided by not using the nfsservctl systemcall at all.
> This is achived by mounting nfsd at /proc/fs/nfsd, and running the latest
> release of nfs-utils.

>From what you say here, it seems that the old nfsservctl systemcall method is  
deprecated and the new method is the one to use.  If this a fact? Would be  
nice to have this documented in the post-halloween document.  I could drop a  
note to Dave Jones to have this change.

BTW:  What version of nfs-utils introduce this new interface for /proc/fs/ 
nfsd?

> *fixing* the problem requires optimising the mount and unmount process,
> which is SEP  (Somebody Elses Problem).

:)

Thanks - JRS


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