Re: [PATCH net-next 3/4] tcp: add SACK compression

On 05/17/2018 08:40 AM, Eric Dumazet wrote:

On 05/17/2018 08:14 AM, Neal Cardwell wrote:

quoted

Any particular motivation for the 2.5ms here? It might be nice to match the
existing TSO autosizing dynamics and use 1ms here instead of having a
separate new constant of 2.5ms. Smaller time scales here should lead to
less burstiness and queue pressure from data packets in the network, and we
know from experience that the CPU overhead of 1ms chunks is acceptable.

This came from my tests on wifi really :)

I also had the idea to make this threshold adjustable for wifi, like we did for sk_pacing_shift.

(On wifi, we might want to increase the max delay between ACK)

So maybe use 1ms delay, when sk_pacing_shift == 10, but increase it if sk_pacing_shift has been lowered.

BTW, maybe my changelog or patch is not clear enough :

As soon as some packets are received in order, we send an ACK, even if the timer was armed.
(This is the beginning of __tcp_ack_snd_check())

When this ACK is sent, timer is canceled (in tcp_event_ack_sent())