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| author | Eric Dumazet <edumazet@google.com> | 2013-12-17 09:58:30 -0800 |
|---|---|---|
| committer | David S. Miller <davem@davemloft.net> | 2013-12-20 17:56:25 -0500 |
| commit | a181ceb501b31b4bf8812a5c84c716cc31d82c2d (patch) | |
| tree | 8233fdcc125262b4985b26ff46d1c58bf2592d1a /drivers/net/ethernet/broadcom/b44.c | |
| parent | a792866ad2dafb8f272e4fdfb98a93fdbfff2277 (diff) | |
| download | lwn-a181ceb501b31b4bf8812a5c84c716cc31d82c2d.tar.gz lwn-a181ceb501b31b4bf8812a5c84c716cc31d82c2d.zip | |
tcp: autocork should not hold first packet in write queue
Willem noticed a TCP_RR regression caused by TCP autocorking
on a Mellanox test bed. MLX4_EN_TX_COAL_TIME is 16 us, which can be
right above RTT between hosts.
We can receive a ACK for a packet still in NIC TX ring buffer or in a
softnet completion queue.
Fix this by always pushing the skb if it is at the head of write queue.
Also, as TX completion is lockless, it's safer to perform sk_wmem_alloc
test after setting TSQ_THROTTLED.
erd:~# MIB="MIN_LATENCY,MEAN_LATENCY,MAX_LATENCY,P99_LATENCY,STDDEV_LATENCY"
erd:~# ./netperf -H remote -t TCP_RR -- -o $MIB | tail -n 1
(repeat 3 times)
Before patch :
18,1049.87,41004,39631,6295.47
17,239.52,40804,48,2912.79
18,348.40,40877,54,3573.39
After patch :
18,22.84,4606,38,16.39
17,21.56,2871,36,13.51
17,22.46,2705,37,11.83
Reported-by: Willem de Bruijn <willemb@google.com>
Signed-off-by: Eric Dumazet <edumazet@google.com>
Fixes: f54b311142a9 ("tcp: auto corking")
Signed-off-by: David S. Miller <davem@davemloft.net>
Diffstat (limited to 'drivers/net/ethernet/broadcom/b44.c')
0 files changed, 0 insertions, 0 deletions