From mboxrd@z Thu Jan  1 00:00:00 1970
From: Trond Myklebust <trond.myklebust@fys.uio.no>
Subject: Re: Urgent help needed on an NFS question, please help!!!
Date: Thu, 10 Aug 2006 20:44:54 -0400
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Cc: Matthew Wilcox <matthew@wil.cx>, Neil Brown <neilb@suse.de>,
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To: Xin Zhao <uszhaoxin@gmail.com>
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On Thu, 2006-08-10 at 18:25 -0400, Xin Zhao wrote:
> The inter-VM inode helps reduce communication cost used to retrieve
> file attributes in a VM environment. In a network environment, it is
> possible for a client to direct see the inode caches of the server.
> But in the virtual server environment, where both client and server
> running on the same physical host, this would be possible.
> 
> If clients have read-only access to server's inode cache, they can
> directly retrieve file attributes without incurring expensive
> getattr() rpc call. Of couse the delegation is able to allow a client
> to trust local cached file attributes without worry about server
> change. But this only works when file is not shared by multiple
> clients. Right? Does NFS4 has some other mechanisms that can further
> improve performance on metadata access?

Not metadata access, no. That would require some seriously messy locking
rules.
It improves performance by allowing a client to access the block device
directly for data reads and writes if it has the capability of doing so.

  Trond