From 1a2881728211f0915c0fa1364770b9c73a67a073 Mon Sep 17 00:00:00 2001 From: Eric Dumazet Date: Thu, 6 Nov 2014 21:10:11 -0800 Subject: [PATCH] mlx4: use napi_complete_done() To enable gro_flush_timeout, a driver has to use napi_complete_done() instead of napi_complete(). Tested: Ran 200 netperf TCP_STREAM from A to B (10Gbe mlx4 link, 8 RX queues) Without this feature, we send back about 305,000 ACK per second. GRO aggregation ratio is low (811/305 = 2.65 segments per GRO packet) Setting a timer of 2000 nsec is enough to increase GRO packet sizes and reduce number of ACK packets. (811/19.2 = 42) Receiver performs less calls to upper stacks, less wakes up. This also reduces cpu usage on the sender, as it receives less ACK packets. Note that reducing number of wakes up increases cpu efficiency, but can decrease QPS, as applications wont have the chance to warmup cpu caches doing a partial read of RPC requests/answers if they fit in one skb. B:~# sar -n DEV 1 10 | grep eth0 | tail -1 Average: eth0 811269.80 305732.30 1199462.57 19705.72 0.00 0.00 0.50 B:~# echo 2000 >/sys/class/net/eth0/gro_flush_timeout B:~# sar -n DEV 1 10 | grep eth0 | tail -1 Average: eth0 811577.30 19230.80 1199916.51 1239.80 0.00 0.00 0.50 Signed-off-by: Eric Dumazet Signed-off-by: David S. Miller --- drivers/net/ethernet/mellanox/mlx4/en_rx.c | 11 ++++------- 1 file changed, 4 insertions(+), 7 deletions(-) diff --git a/drivers/net/ethernet/mellanox/mlx4/en_rx.c b/drivers/net/ethernet/mellanox/mlx4/en_rx.c index b173a0cf44e0..46ee78326f1f 100644 --- a/drivers/net/ethernet/mellanox/mlx4/en_rx.c +++ b/drivers/net/ethernet/mellanox/mlx4/en_rx.c @@ -915,15 +915,12 @@ int mlx4_en_poll_rx_cq(struct napi_struct *napi, int budget) * probably affinity changed. need to stop this NAPI * poll, and restart it on the right CPU */ - napi_complete(napi); - mlx4_en_arm_cq(priv, cq); - return 0; + done = 0; } - } else { - /* Done for now */ - napi_complete(napi); - mlx4_en_arm_cq(priv, cq); } + /* Done for now */ + napi_complete_done(napi, done); + mlx4_en_arm_cq(priv, cq); return done; } -- 2.20.1