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

Chuck Lever
2015-07-10T15:59:25Z

On Jul 10, 2015, at 11:54 AM, J. Bruce Fields <bfields@fieldses.org> wrote:

> On Fri, Jul 10, 2015 at 10:59:48AM -0400, Chuck Lever wrote:
>>
>> On Jul 10, 2015, at 10:18 AM, bfields@fieldses.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.
>
> But there'd be no reason to do that, because we're not using
> RPCRDMA_MAX_SVC_SEGS anywhere. Should we be?

Let me try using RPCSVC_MAXPAYLOAD. That is based on RPCSVC_MAXPAGES,
which is actually used in svc_rdma_*.c

> --b.
>
>>
>>
>>> --b.
>>>
>>>>
>>>> Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
>>>> ---
>>>>
>>>> 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
>>>>
>>>> --
>>>> To unsubscribe from this list: send the line "unsubscribe linux-nfs" in
>>>> the body of a message to majordomo@vger.kernel.org
>>>> More majordomo info at http://vger.kernel.org/majordomo-info.html
>>
>> --
>> Chuck Lever
>>
>>

--
Chuck Lever