Commit a682850a authored Nov 11, 2018 by Eric Dumazet Committed by David S. Miller Nov 11, 2018

tcp: get rid of tcp_tso_should_defer() dependency on HZ/jiffies



tcp_tso_should_defer() first heuristic is to not defer
if last send is "old enough".

Its current implementation uses jiffies and its low granularity.

TSO autodefer performance should not rely on kernel HZ :/

After EDT conversion, we have state variables in nanoseconds that
can allow us to properly implement the heuristic.

This patch increases TSO chunk sizes on medium rate flows,
especially when receivers do not use GRO or similar aggregation.

It also reduces bursts for HZ=100 or HZ=250 kernels, making TCP
behavior more uniform.

Signed-off-by: Eric Dumazet <edumazet@google.com>
Acked-by: Soheil Hassas Yeganeh <soheil@google.com>
Acked-by: Neal Cardwell <ncardwell@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

parent f1c6ea38

net/ipv4/tcp_output.c

+5 −2

Original line number	Diff line number	Diff line
		@@ -1920,9 +1920,12 @@ static bool tcp_tso_should_defer(struct sock sk, struct sk_buff skb,
		goto send_now;

		/* Avoid bursty behavior by allowing defer
		* only if the last write was recent.
		* only if the last write was recent (1 ms).
		* Note that tp->tcp_wstamp_ns can be in the future if we have
		* packets waiting in a qdisc or device for EDT delivery.
		*/
		if ((s32)(tcp_jiffies32 - tp->lsndtime) > 0)
		delta = tp->tcp_clock_cache - tp->tcp_wstamp_ns - NSEC_PER_MSEC;
		if (delta > 0)
		goto send_now;

		in_flight = tcp_packets_in_flight(tp);

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