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

J. Bruce Fields
2015-07-10T15:54:24Z

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?

--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