Re: [PATCH v5 19/19] SUNRPC: Bump the maximum payload size for the server

Chuck Lever
2025-05-12T18:09:09Z

On 5/12/25 12:44 PM, Aurélien Couderc wrote:
> Could this patch series - minus the change to the default of 1MB - be
> promoted to Linux 6.6 LongTermSupport, please?

It has to be merged upstream first.

But, new features are generally not backported to stable. At this time,
this feature is intended only for future kernels.

> Aurélien
>
> On Fri, May 9, 2025 at 9:06 PM <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.
>>
>> An API to adjust the operational maximum was added in 2006 by commit
>> 596bbe53eb3a ("[PATCH] knfsd: Allow max size of NFSd payload to be
>> configured"). To adjust the operational maximum using this API, shut
>> down the NFS server. Then echo a new value into:
>>
>> /proc/fs/nfsd/max_block_size
>>
>> And restart the NFS server.
>>
>> Reviewed-by: Jeff Layton <jlayton@kernel.org>
>> Reviewed-by: NeilBrown <neil@brown.name>
>> Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
>> ---
>> include/linux/sunrpc/svc.h | 14 +++++++-------
>> 1 file changed, 7 insertions(+), 7 deletions(-)
>>
>> diff --git a/include/linux/sunrpc/svc.h b/include/linux/sunrpc/svc.h
>> index d57df042e24a..48666b83fe68 100644
>> --- a/include/linux/sunrpc/svc.h
>> +++ b/include/linux/sunrpc/svc.h
>> @@ -119,14 +119,14 @@ void svc_destroy(struct svc_serv **svcp);
>> * Linux limit; someone who cares more about NFS/UDP performance
>> * can test a larger number.
>> *
>> - * For TCP transports we have more freedom. A size of 1MB is
>> - * chosen to match the client limit. Other OSes are known to
>> - * have larger limits, but those numbers are probably beyond
>> - * the point of diminishing returns.
>> + * For non-UDP transports we have more freedom. A size of 4MB is
>> + * chosen to accommodate clients that support larger I/O sizes.
>> */
>> -#define RPCSVC_MAXPAYLOAD (1*1024*1024u)
>> -#define RPCSVC_MAXPAYLOAD_TCP RPCSVC_MAXPAYLOAD
>> -#define RPCSVC_MAXPAYLOAD_UDP (32*1024u)
>> +enum {
>> + RPCSVC_MAXPAYLOAD = 4 * 1024 * 1024,
>> + RPCSVC_MAXPAYLOAD_TCP = RPCSVC_MAXPAYLOAD,
>> + RPCSVC_MAXPAYLOAD_UDP = 32 * 1024,
>> +};
>>
>> extern u32 svc_max_payload(const struct svc_rqst *rqstp);
>>
>> --
>> 2.49.0
>>
>>
>
>

--
Chuck Lever