Re: [RFC PATCH 0/7] sunrpc: Reduce lock contention for NFSD TCP sockets

[Mike Snitzer <snitzer@kernel.org>]

Hi Chuck,

On Thu, Feb 05, 2026 at 10:57:22AM -0500, Chuck Lever wrote:
> From: Chuck Lever <chuck.lever@oracle.com>
> 
> High-throughput NFSD workloads exhibit significant lock contention on
> TCP connections. Worker threads compete for the socket lock during
> receives and serialize on xpt_mutex during sends, limiting scalability.
> 
> This series addresses both paths:
> 
>  - Receive: A dedicated kernel thread per TCP connection owns all
>    sock_recvmsg() calls and queues complete RPC messages for workers
>    via lock-free llist. This eliminates socket lock contention among
>    workers.
> 
>  - Transmit: Flat combining allows one thread to send on behalf of
>    multiple waiters. Threads enqueue requests; the mutex holder
>    ("combiner") processes the batch, amortizing lock acquisition and
>    enabling TCP segment coalescing via MSG_MORE.
> 
> Supporting changes include a workqueue affinity fix for single-LLC
> systems, a page recycling pool for receive buffers, and explicit TCP
> buffer sizing for high bandwidth-delay product networks.
> 
> Base commit: v6.19-rc8
> 
> ---
> 
> Chuck Lever (7):
>   workqueue: Automatic affinity scope fallback for single-pod topologies
>   sunrpc: split svc_data_ready into protocol-specific callbacks
>   sunrpc: add per-transport page recycling pool
>   sunrpc: add dedicated TCP receiver thread
>   sunrpc: implement flat combining for TCP socket sends
>   sunrpc: unify fore and backchannel server TCP send paths
>   SUNRPC: Set explicit TCP socket buffer sizes for NFSD

Curious to know your thinking on this patchset?  Can you post v2 given
your note about having adapted based on Tejun's feedback here?

https://lore.kernel.org/linux-nfs/af3a034c-4829-469d-b55d-9414409ee425@app.fastmail.com/

Thanks,
Mike