Subject: Re: directory delegations
To:     "J. Bruce Fields" <bfields@fieldses.org>
Cc:     linux-nfs@vger.kernel.org
References: <2065755c-f888-9c62-f6e5-f143d42c51ee@oracle.com>
 <20190402161116.GA2828@fieldses.org>
From:   "Bradley C. Kuszmaul" <bradley.kuszmaul@oracle.com>
Message-ID: <2f1f6582-3672-1361-4392-80cb1e62e19c@oracle.com>
Date:   Tue, 2 Apr 2019 13:26:19 -0400
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My simple model of metadata operations is to untar something like the 
linux sources.

Each file incurs a LOOKUP, CREATE, SETATTR, and WRITE, each of which is 
fairly high latency (even the WRITE ends up being done essentially 
synchronously because tar closes the file after its write(2) call.)

I guess directory delegations might save the cost of LOOKUP.

Is there any hope for getting write delegations?

What other steps might be possible?

-Bradley

On 4/2/19 12:11 PM, bfields@fieldses.org wrote:
> On Mon, Apr 01, 2019 at 12:21:49PM -0400, Bradley C. Kuszmaul wrote:
>> Hi, I'm the architect for Oracle's File Storage Service.   FSS is
>> basically a big scalable NFS server that runs in Oracle's cloud.
>>
>> Our metadata operations have higher latency than a vanilla NFS
>> server (e.g., a Linux NFS server serving a XFS stored on a block
>> device), and we suspect that directory delegations would make a big
>> performance improvement.
>>
>> I understand, however, that essentially no one implements directory
>> delegations.
>>
>> Can anyone fill me in on the current thinking of the future of
>> support for directory delegations in the Linux NFS client?
> Maybe somebody else will speak up, but I don't know of any effort to
> implement directory delegations.
>
> What metadata operations specifically are you worried about?  The
> directory delegations that are specified in RFC 5661 are read-only.
> Which might explain some of the lack of interest.
>
> But there may be other steps that we could take to improve matters.
>
> --b.