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author | Eric Dumazet <edumazet@google.com> | 2017-12-10 17:55:04 -0800 |
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committer | David S. Miller <davem@davemloft.net> | 2017-12-12 10:53:04 -0500 |
commit | c3916ad9320eed8eacd7c0b2cf7f881efceda892 (patch) | |
tree | a4fdf9cc629e3e5d300c58b80626059e2ac99437 /sound/isa/msnd | |
parent | 607065bad9931e72207b0cac365d7d4abc06bd99 (diff) | |
download | linux-next-c3916ad9320eed8eacd7c0b2cf7f881efceda892.tar.gz |
tcp: smoother receiver autotuning
Back in linux-3.13 (commit b0983d3c9b13 ("tcp: fix dynamic right sizing"))
I addressed the pressing issues we had with receiver autotuning.
But DRS suffers from extra latencies caused by rcv_rtt_est.rtt_us
drifts. One common problem happens during slow start, since the
apparent RTT measured by the receiver can be inflated by ~50%,
at the end of one packet train.
Also, a single drop can delay read() calls by one RTT, meaning
tcp_rcv_space_adjust() can be called one RTT too late.
By replacing the tri-modal heuristic with a continuous function,
we can offset the effects of not growing 'at the optimal time'.
The curve of the function matches prior behavior if the space
increased by 25% and 50% exactly.
Cost of added multiply/divide is small, considering a TCP flow
typically would run this part of the code few times in its life.
I tested this patch with 100 ms RTT / 1% loss link, 100 runs
of (netperf -l 5), and got an average throughput of 4600 Mbit
instead of 1700 Mbit.
Signed-off-by: Eric Dumazet <edumazet@google.com>
Acked-by: Soheil Hassas Yeganeh <soheil@google.com>
Acked-by: Wei Wang <weiwan@google.com>
Acked-by: Neal Cardwell <ncardwell@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Diffstat (limited to 'sound/isa/msnd')
0 files changed, 0 insertions, 0 deletions