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| author |   Eric Dumazet <edumazet@google.com> | 2018-04-16 10:33:37 -0700 |
|---|---|---|
| committer |   David S. Miller <davem@davemloft.net> | 2018-04-16 18:26:37 -0400 |
| commit | 03f45c883c6f391ed4fff8292415b35bd1107519 (patch) | |
| tree | 826d80967d0b56f08e19072b7fa5810aa03ca667 /net/ipv4/af_inet.c | |
| parent | tcp: fix delayed acks behavior for SO_RCVLOWAT (diff) | |
| download | linux-dev-03f45c883c6f391ed4fff8292415b35bd1107519.tar.xz linux-dev-03f45c883c6f391ed4fff8292415b35bd1107519.zip | |
tcp: avoid extra wakeups for SO_RCVLOWAT users
SO_RCVLOWAT is properly handled in tcp_poll(), so that POLLIN is only
generated when enough bytes are available in receive queue, after
David change (commit c7004482e8dc "tcp: Respect SO_RCVLOWAT in tcp_poll().")
But TCP still calls sk->sk_data_ready() for each chunk added in receive
queue, meaning thread is awaken, and goes back to sleep shortly after.
Tested:
tcp_mmap test program, receiving 32768 MB of data with SO_RCVLOWAT set to 512KB
-> Should get ~2 wakeups (c-switches) per MB, regardless of how many
(tiny or big) packets were received.
High speed (mostly full size GRO packets)
received 32768 MB (100 % mmap'ed) in 8.03112 s, 34.2266 Gbit,
cpu usage user:0.037 sys:1.404, 43.9758 usec per MB, 65497 c-switches
received 32768 MB (99.9954 % mmap'ed) in 7.98453 s, 34.4263 Gbit,
cpu usage user:0.03 sys:1.422, 44.3115 usec per MB, 65485 c-switches
Low speed (sender is ratelimited and sends 1-MSS at a time, so GRO is not helping)
received 22474.5 MB (100 % mmap'ed) in 6015.35 s, 0.0313414 Gbit,
cpu usage user:0.05 sys:1.586, 72.7952 usec per MB, 44950 c-switches
Signed-off-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Diffstat (limited to 'net/ipv4/af_inet.c')
0 files changed, 0 insertions, 0 deletions