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

J. Bruce Fields
2015-07-10T16:05:06Z

On Fri, Jul 10, 2015 at 11:59:20AM -0400, Chuck Lever wrote:
>
> On Jul 10, 2015, at 11:54 AM, J. Bruce Fields <bfields-uC3wQj2KruNg9hUCZPvPmw@public.gmane.org> wrote:
>
> > On Fri, Jul 10, 2015 at 10:59:48AM -0400, Chuck Lever wrote:
> >>
> >> 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.
> >
> > 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

OK, thanks, that sounds like that would make more sense.

--b.

>
>
> > --b.
> >
> >>
> >>
> >>> --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
> >>
> >>
>
> --
> Chuck Lever