Re: [PATCH v4 14/14] SUNRPC: Bump the maximum payload size for the server

Chuck Lever
2025-05-06T13:59:36Z

On 5/6/25 9:54 AM, Jeff Layton wrote:
> On Tue, 2025-05-06 at 09:52 -0400, Chuck Lever wrote:
>> On 5/6/25 9:34 AM, Christoph Hellwig wrote:
>>> On Mon, Apr 28, 2025 at 03:37:02PM -0400, cel@kernel.org wrote:
>>>> From: Chuck Lever <chuck.lever@oracle.com>
>>>>
>>>> Increase the maximum server-side RPC payload to 4MB. The default
>>>> remains at 1MB.
>>>>
>>>> To adjust the operational maximum, shut down the NFS server. Then
>>>> echo a new value into:
>>>>
>>>> /proc/fs/nfsd/max_block_size
>>>>
>>>> And restart the NFS server.
>>>
>>> Are you going to wire this up to a config file in nfs-utils that
>>> gets set before the daemon starts?
>>
>> That's up to SteveD -- it might be added to /etc/nfs.conf.
>>
>>
>
> Can we also add this to the netlink interface for nfsd and nfsdctl?

Sure, that's possible, however:

The purpose of this series is only to enable experimentation (aside from
the other nice clean-ups).

Once that is complete, what are the use cases for admins to increase or
decrease this value? (Not a rhetorical question: I'd like to invite some
discussion about that).

As always, these interfaces need documentation and long-term support. I
would like to get some technical rationale on the table before we
commit to the support costs.

>>> Because otherwise this is a pretty horrible user interface.
>>
>> This is an API that has existed forever.
>>
>> I don't even like that this maximum can be tuned. After a period of
>> experimentation, I was going to set the default to a higher value and
>> be done with it, because I can't think of a reason why it needs to be
>> shifted up or down after that.
>>
>

--
Chuck Lever