Re: [PATCH v1 5/5] svcrdma: Boost NFS READ/WRITE payload size maximum

Chuck Lever
2015-07-10T14:59:48Z

On Jul 10, 2015, at 10:18 AM, bfields-uC3wQj2KruNg9hUCZPvPmw@public.gmane.org wrote:

> On Thu, Jul 09, 2015 at 04:45:47PM -0400, Chuck Lever wrote:
>> Increased to 1 megabyte.
>
> Why not more or less?
>
> Why do we even have this constant, why shouldn't we just use
> RPCSVC_MAXPAYLOAD?

The payload size maximum for RDMA is based on RPCRDMA_MAX_SVC_SEGS.
We could reverse the relationship and make RPCRDMA_MAX_SVC_SEGS
based on RPCSVC_MAXPAYLOAD divided by the platform’s page size.

> --b.
>
>>
>> Signed-off-by: Chuck Lever <chuck.lever-QHcLZuEGTsvQT0dZR+AlfA@public.gmane.org>
>> ---
>>
>> include/linux/sunrpc/svc_rdma.h | 2 +-
>> 1 files changed, 1 insertions(+), 1 deletions(-)
>>
>> diff --git a/include/linux/sunrpc/svc_rdma.h b/include/linux/sunrpc/svc_rdma.h
>> index 13af61b..1bca6dd 100644
>> --- a/include/linux/sunrpc/svc_rdma.h
>> +++ b/include/linux/sunrpc/svc_rdma.h
>> @@ -172,7 +172,7 @@ struct svcxprt_rdma {
>> #define RDMAXPRT_SQ_PENDING 2
>> #define RDMAXPRT_CONN_PENDING 3
>>
>> -#define RPCRDMA_MAX_SVC_SEGS (64) /* server max scatter/gather */
>> +#define RPCRDMA_MAX_SVC_SEGS (256) /* server max scatter/gather */
>> #if RPCSVC_MAXPAYLOAD < (RPCRDMA_MAX_SVC_SEGS << PAGE_SHIFT)
>> #define RPCRDMA_MAXPAYLOAD RPCSVC_MAXPAYLOAD
>> #else
>>
>> --
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--
Chuck Lever