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Subject[PATCH net-next 1/2] net/smc: send cdc msg inline if qp has sufficient inline space
Date
As cdc msg's length is 44B, cdc msgs can be sent inline in
most rdma devices, which can help reducing sending latency.

In my test environment, which are 2 VMs running on the same
physical host and whose NICs(ConnectX-4Lx) are working on
SR-IOV mode, qperf shows 0.4us-0.7us improvement in latency.

Test command:
server: smc_run taskset -c 1 qperf
client: smc_run taskset -c 1 qperf <server ip> -oo \
msg_size:1:2K:*2 -t 30 -vu tcp_lat

The results shown below:
msgsize before after
1B 11.9 us 11.2 us (-0.7 us)
2B 11.7 us 11.2 us (-0.5 us)
4B 11.7 us 11.3 us (-0.4 us)
8B 11.6 us 11.2 us (-0.4 us)
16B 11.7 us 11.3 us (-0.4 us)
32B 11.7 us 11.3 us (-0.4 us)
64B 11.7 us 11.2 us (-0.5 us)
128B 11.6 us 11.2 us (-0.4 us)
256B 11.8 us 11.2 us (-0.6 us)
512B 11.8 us 11.4 us (-0.4 us)
1KB 11.9 us 11.4 us (-0.5 us)
2KB 12.1 us 11.5 us (-0.6 us)

Signed-off-by: Guangguan Wang <guangguan.wang@linux.alibaba.com>
---
net/smc/smc_ib.c | 1 +
net/smc/smc_wr.c | 5 ++++-
2 files changed, 5 insertions(+), 1 deletion(-)

diff --git a/net/smc/smc_ib.c b/net/smc/smc_ib.c
index a3e2d3b89568..1dcce9e4f4ca 100644
--- a/net/smc/smc_ib.c
+++ b/net/smc/smc_ib.c
@@ -671,6 +671,7 @@ int smc_ib_create_queue_pair(struct smc_link *lnk)
.max_recv_wr = SMC_WR_BUF_CNT * 3,
.max_send_sge = SMC_IB_MAX_SEND_SGE,
.max_recv_sge = sges_per_buf,
+ .max_inline_data = SMC_WR_TX_SIZE,
},
.sq_sig_type = IB_SIGNAL_REQ_WR,
.qp_type = IB_QPT_RC,
diff --git a/net/smc/smc_wr.c b/net/smc/smc_wr.c
index 24be1d03fef9..8a2f9a561197 100644
--- a/net/smc/smc_wr.c
+++ b/net/smc/smc_wr.c
@@ -554,10 +554,11 @@ void smc_wr_remember_qp_attr(struct smc_link *lnk)
static void smc_wr_init_sge(struct smc_link *lnk)
{
int sges_per_buf = (lnk->lgr->smc_version == SMC_V2) ? 2 : 1;
+ bool send_inline = (lnk->qp_attr.cap.max_inline_data >= SMC_WR_TX_SIZE);
u32 i;

for (i = 0; i < lnk->wr_tx_cnt; i++) {
- lnk->wr_tx_sges[i].addr =
+ lnk->wr_tx_sges[i].addr = send_inline ? (u64)(&lnk->wr_tx_bufs[i]) :
lnk->wr_tx_dma_addr + i * SMC_WR_BUF_SIZE;
lnk->wr_tx_sges[i].length = SMC_WR_TX_SIZE;
lnk->wr_tx_sges[i].lkey = lnk->roce_pd->local_dma_lkey;
@@ -575,6 +576,8 @@ static void smc_wr_init_sge(struct smc_link *lnk)
lnk->wr_tx_ibs[i].opcode = IB_WR_SEND;
lnk->wr_tx_ibs[i].send_flags =
IB_SEND_SIGNALED | IB_SEND_SOLICITED;
+ if (send_inline)
+ lnk->wr_tx_ibs[i].send_flags |= IB_SEND_INLINE;
lnk->wr_tx_rdmas[i].wr_tx_rdma[0].wr.opcode = IB_WR_RDMA_WRITE;
lnk->wr_tx_rdmas[i].wr_tx_rdma[1].wr.opcode = IB_WR_RDMA_WRITE;
lnk->wr_tx_rdmas[i].wr_tx_rdma[0].wr.sg_list =
--
2.24.3 (Apple Git-128)
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