From da4e8648079eb6f26f3a88d8c34270a057e2bfe6 Mon Sep 17 00:00:00 2001 From: Long Li Date: Mon, 17 Jul 2023 12:35:38 -0700 Subject: [PATCH 1/2] net: mana: Batch ringing RX queue doorbell on receiving packets It's inefficient to ring the doorbell page every time a WQE is posted to the received queue. Excessive MMIO writes result in CPU spending more time waiting on LOCK instructions (atomic operations), resulting in poor scaling performance. Move the code for ringing doorbell page to where after we have posted all WQEs to the receive queue during a callback from napi_poll(). With this change, tests showed an improvement from 120G/s to 160G/s on a 200G physical link, with 16 or 32 hardware queues. Tests showed no regression in network latency benchmarks on single connection. Reviewed-by: Haiyang Zhang Reviewed-by: Dexuan Cui Signed-off-by: Long Li Link: https://lore.kernel.org/r/1689622539-5334-2-git-send-email-longli@linuxonhyperv.com Signed-off-by: Jakub Kicinski --- drivers/net/ethernet/microsoft/mana/mana_en.c | 10 ++++++++-- 1 file changed, 8 insertions(+), 2 deletions(-) diff --git a/drivers/net/ethernet/microsoft/mana/mana_en.c b/drivers/net/ethernet/microsoft/mana/mana_en.c index a499e460594b6..ac2acc9aca9d0 100644 --- a/drivers/net/ethernet/microsoft/mana/mana_en.c +++ b/drivers/net/ethernet/microsoft/mana/mana_en.c @@ -1386,8 +1386,8 @@ static void mana_post_pkt_rxq(struct mana_rxq *rxq) recv_buf_oob = &rxq->rx_oobs[curr_index]; - err = mana_gd_post_and_ring(rxq->gdma_rq, &recv_buf_oob->wqe_req, - &recv_buf_oob->wqe_inf); + err = mana_gd_post_work_request(rxq->gdma_rq, &recv_buf_oob->wqe_req, + &recv_buf_oob->wqe_inf); if (WARN_ON_ONCE(err)) return; @@ -1657,6 +1657,12 @@ static void mana_poll_rx_cq(struct mana_cq *cq) mana_process_rx_cqe(rxq, cq, &comp[i]); } + if (comp_read > 0) { + struct gdma_context *gc = rxq->gdma_rq->gdma_dev->gdma_context; + + mana_gd_wq_ring_doorbell(gc, rxq->gdma_rq); + } + if (rxq->xdp_flush) xdp_do_flush(); } From f5e39b57124fd4715d7f0e2f841b8609b38f3e40 Mon Sep 17 00:00:00 2001 From: Long Li Date: Mon, 17 Jul 2023 12:35:39 -0700 Subject: [PATCH 2/2] net: mana: Use the correct WQE count for ringing RQ doorbell The hardware specification specifies that WQE_COUNT should set to 0 for the Receive Queue. Although currently the hardware doesn't enforce the check, in the future releases it may check on this value. Reviewed-by: Haiyang Zhang Reviewed-by: Dexuan Cui Signed-off-by: Long Li Link: https://lore.kernel.org/r/1689622539-5334-3-git-send-email-longli@linuxonhyperv.com Signed-off-by: Jakub Kicinski --- drivers/net/ethernet/microsoft/mana/gdma_main.c | 5 ++++- 1 file changed, 4 insertions(+), 1 deletion(-) diff --git a/drivers/net/ethernet/microsoft/mana/gdma_main.c b/drivers/net/ethernet/microsoft/mana/gdma_main.c index 8f3f78b685922..3765d3389a9a0 100644 --- a/drivers/net/ethernet/microsoft/mana/gdma_main.c +++ b/drivers/net/ethernet/microsoft/mana/gdma_main.c @@ -300,8 +300,11 @@ static void mana_gd_ring_doorbell(struct gdma_context *gc, u32 db_index, void mana_gd_wq_ring_doorbell(struct gdma_context *gc, struct gdma_queue *queue) { + /* Hardware Spec specifies that software client should set 0 for + * wqe_cnt for Receive Queues. This value is not used in Send Queues. + */ mana_gd_ring_doorbell(gc, queue->gdma_dev->doorbell, queue->type, - queue->id, queue->head * GDMA_WQE_BU_SIZE, 1); + queue->id, queue->head * GDMA_WQE_BU_SIZE, 0); } void mana_gd_ring_cq(struct gdma_queue *cq, u8 arm_bit)