diff options
| author | Chuck Lever <chuck.lever@oracle.com> | 2026-03-06 16:56:27 -0500 |
|---|---|---|
| committer | Trond Myklebust <trond.myklebust@hammerspace.com> | 2026-04-13 12:05:00 -0700 |
| commit | 93b4791adb1017b2b079b4a453e7159e101a7e55 (patch) | |
| tree | b0b3bb3420693f9ea0e00878c3a0f75252e35202 | |
| parent | 7a079ab57c4eeff241d9abfc1ec6477cb90a6206 (diff) | |
xprtrdma: Scale receive batch size with credit window
The fixed RPCRDMA_MAX_RECV_BATCH of 7 results in frequent
small ib_post_recv batches during high-rate workloads. With
a 128-slot credit window, receives are reposted every 7th
completion, each batch incurring atomic serialization and a
doorbell write.
Replace the fixed batch constant with a per-endpoint value
scaled to 25% of the negotiated credit window. For a typical
128-credit connection this raises the batch from 7 to 32,
reducing doorbell frequency by roughly 4x and amortizing the
per-batch atomic and MMIO costs over a larger group of
receive WRs.
Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
Signed-off-by: Trond Myklebust <trond.myklebust@hammerspace.com>
| -rw-r--r-- | net/sunrpc/xprtrdma/frwr_ops.c | 3 | ||||
| -rw-r--r-- | net/sunrpc/xprtrdma/verbs.c | 2 | ||||
| -rw-r--r-- | net/sunrpc/xprtrdma/xprt_rdma.h | 1 |
3 files changed, 4 insertions, 2 deletions
diff --git a/net/sunrpc/xprtrdma/frwr_ops.c b/net/sunrpc/xprtrdma/frwr_ops.c index 229057d35fb8..7f79a0a2601e 100644 --- a/net/sunrpc/xprtrdma/frwr_ops.c +++ b/net/sunrpc/xprtrdma/frwr_ops.c @@ -244,9 +244,10 @@ int frwr_query_device(struct rpcrdma_ep *ep, const struct ib_device *device) } ep->re_attr.cap.max_send_wr += RPCRDMA_BACKWARD_WRS; ep->re_attr.cap.max_send_wr += 1; /* for ib_drain_sq */ + ep->re_recv_batch = ep->re_max_requests >> 2; ep->re_attr.cap.max_recv_wr = ep->re_max_requests; ep->re_attr.cap.max_recv_wr += RPCRDMA_BACKWARD_WRS; - ep->re_attr.cap.max_recv_wr += RPCRDMA_MAX_RECV_BATCH; + ep->re_attr.cap.max_recv_wr += ep->re_recv_batch; ep->re_attr.cap.max_recv_wr += 1; /* for ib_drain_rq */ ep->re_max_rdma_segs = diff --git a/net/sunrpc/xprtrdma/verbs.c b/net/sunrpc/xprtrdma/verbs.c index 90fd83f2d846..aecf9c0a153f 100644 --- a/net/sunrpc/xprtrdma/verbs.c +++ b/net/sunrpc/xprtrdma/verbs.c @@ -1374,7 +1374,7 @@ void rpcrdma_post_recvs(struct rpcrdma_xprt *r_xprt, int needed) if (likely(ep->re_receive_count > needed)) goto out; needed -= ep->re_receive_count; - needed += RPCRDMA_MAX_RECV_BATCH; + needed += ep->re_recv_batch; if (atomic_inc_return(&ep->re_receiving) > 1) goto out_dec; diff --git a/net/sunrpc/xprtrdma/xprt_rdma.h b/net/sunrpc/xprtrdma/xprt_rdma.h index 37bba72065e8..f53a77472724 100644 --- a/net/sunrpc/xprtrdma/xprt_rdma.h +++ b/net/sunrpc/xprtrdma/xprt_rdma.h @@ -96,6 +96,7 @@ struct rpcrdma_ep { struct rpcrdma_notification re_rn; int re_receive_count; unsigned int re_max_requests; /* depends on device */ + unsigned int re_recv_batch; unsigned int re_inline_send; /* negotiated */ unsigned int re_inline_recv; /* negotiated */ |