Post RECV WRs in batches to reduce the hardware doorbell rate per transport. This helps the RPC-over-RDMA client scale better in number of transports. Signed-off-by: Chuck Lever <chuck.lever@xxxxxxxxxx> --- net/sunrpc/xprtrdma/verbs.c | 2 ++ net/sunrpc/xprtrdma/xprt_rdma.h | 10 ++++++++++ 2 files changed, 12 insertions(+) diff --git a/net/sunrpc/xprtrdma/verbs.c b/net/sunrpc/xprtrdma/verbs.c index 4994e75..b4e997d 100644 --- a/net/sunrpc/xprtrdma/verbs.c +++ b/net/sunrpc/xprtrdma/verbs.c @@ -1480,6 +1480,8 @@ struct rpcrdma_regbuf * if (ep->rep_receive_count > needed) goto out; needed -= ep->rep_receive_count; + if (!temp) + needed += RPCRDMA_MAX_RECV_BATCH; count = 0; wr = NULL; diff --git a/net/sunrpc/xprtrdma/xprt_rdma.h b/net/sunrpc/xprtrdma/xprt_rdma.h index 33db208..10f6593 100644 --- a/net/sunrpc/xprtrdma/xprt_rdma.h +++ b/net/sunrpc/xprtrdma/xprt_rdma.h @@ -205,6 +205,16 @@ struct rpcrdma_rep { struct ib_recv_wr rr_recv_wr; }; +/* To reduce the rate at which a transport invokes ib_post_recv + * (and thus the hardware doorbell rate), xprtrdma posts Receive + * WRs in batches. + * + * Setting this to zero disables Receive post batching. + */ +enum { + RPCRDMA_MAX_RECV_BATCH = 7, +}; + /* struct rpcrdma_sendctx - DMA mapped SGEs to unmap after Send completes */ struct rpcrdma_req;