On Thu, Jul 21, 2011 at 01:49:02PM -0400, Steve Dickson wrote:
> Our performance team has noticed that increasing
> RPCRDMA_MAX_DATA_SEGS from 8 to 64 significantly
> increases throughput when using the RDMA transport.
The main risk that I can see being that we have on the stack in two
places:
rpcrdma_register_fmr_external(struct rpcrdma_mr_seg *seg, ...
{
...
u64 physaddrs[RPCRDMA_MAX_DATA_SEGS];
rpcrdma_register_default_external(struct rpcrdma_mr_seg *seg, ...
{
...
struct ib_phys_buf ipb[RPCRDMA_MAX_DATA_SEGS];
Where ip_phys_buf is 16 bytes.
So that's 512 bytes in the first case, 1024 in the second. This is
called from rpciod--what are our rules about allocating memory from
rpciod?
--b.
>
> Signed-off-by: Steve Dickson <steved@xxxxxxxxxx>
> ---
> net/sunrpc/xprtrdma/xprt_rdma.h | 2 +-
> 1 files changed, 1 insertions(+), 1 deletions(-)
>
> diff --git a/net/sunrpc/xprtrdma/xprt_rdma.h b/net/sunrpc/xprtrdma/xprt_rdma.h
> index cae761a..5d1cfe5 100644
> --- a/net/sunrpc/xprtrdma/xprt_rdma.h
> +++ b/net/sunrpc/xprtrdma/xprt_rdma.h
> @@ -109,7 +109,7 @@ struct rpcrdma_ep {
> */
>
> /* temporary static scatter/gather max */
> -#define RPCRDMA_MAX_DATA_SEGS (8) /* max scatter/gather */
> +#define RPCRDMA_MAX_DATA_SEGS (64) /* max scatter/gather */
> #define RPCRDMA_MAX_SEGS (RPCRDMA_MAX_DATA_SEGS + 2) /* head+tail = 2 */
> #define MAX_RPCRDMAHDR (\
> /* max supported RPC/RDMA header */ \
> --
> 1.7.6
>
> --
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