Re: [PATCH net] tcp: fix receive buffer autotuning to trigger for any valid advertised MSS

On Mon, 7 Dec 2020 11:46:25 +0000 Hazem Mohamed Abuelfotoh wrote:

Previously receiver buffer auto-tuning starts after receiving
one advertised window amount of data.After the initial
receiver buffer was raised by
commit a337531b942b ("tcp: up initial rmem to 128KB
and SYN rwin to around 64KB"),the receiver buffer may
take too long for TCP autotuning to start raising
the receiver buffer size.
commit 041a14d26715 ("tcp: start receiver buffer autotuning sooner")
tried to decrease the threshold at which TCP auto-tuning starts
but it's doesn't work well in some environments
where the receiver has large MTU (9001) especially with high RTT
connections as in these environments rcvq_space.space will be the same
as rcv_wnd so TCP autotuning will never start because
sender can't send more than rcv_wnd size in one round trip.
To address this issue this patch is decreasing the initial
rcvq_space.space so TCP autotuning kicks in whenever the sender is
able to send more than 5360 bytes in one round trip regardless the
receiver's configured MTU.

Fixes: a337531b942b ("tcp: up initial rmem to 128KB and SYN rwin to around 64KB")
Fixes: 041a14d26715 ("tcp: start receiver buffer autotuning sooner")

Signed-off-by: Hazem Mohamed Abuelfotoh abuehaze@amazon.com

If the discussion concludes in favor of this patch please un-indent this commit message, remove the empty line after the fixes tag, and repost.