* TCP get SND_CWND change on loss event
@ 2017-05-27 12:08 Lars Erik Storbukås
2017-05-27 12:10 ` Willy Tarreau
0 siblings, 1 reply; 2+ messages in thread
From: Lars Erik Storbukås @ 2017-05-27 12:08 UTC (permalink / raw)
To: LKML
I want to store the value of snd_cwnd when a congestion event occurs
(value before snd_cwnd is reduced), and the new value of snd_cwnd (the
value it has been reduced to). In other words: the congestion window
before and after a congestion event occurs.
I'm uncertain where (and how) it would be logical to implement this. I
have found two possible locations in the tcp_input.c where (I think)
it could be implemented:
static void tcp_cong_control(...) {
...
if (tcp_in_cwnd_reduction(sk)) {
struct tcp_sock *tp = tcp_sk(sk);
prior_congestion_window = tp->snd_cwnd;
/* Reduce cwnd if state mandates */
tcp_cwnd_reduction(sk, acked_sacked, flag);
reduced_congestion_window = tp->snd_cwnd;
}
...
}
or
static void tcp_fastretrans_alert(...) {
...
default:
...
struct tcp_sock *tp = tcp_sk(sk);
prior_congestion_window = tp->snd_cwnd;
/* Otherwise enter Recovery state */
tcp_enter_recovery(sk, (flag & FLAG_ECE));
fast_rexmit = 1;
reduced_congestion_window = tp->snd_cwnd;
...
}
Does anyone have advice on where (and how) to implement this? Does any
of the proposed solutions above seem logical?
/ Lars Erik Storbukås
^ permalink raw reply [flat|nested] 2+ messages in thread
* Re: TCP get SND_CWND change on loss event
2017-05-27 12:08 TCP get SND_CWND change on loss event Lars Erik Storbukås
@ 2017-05-27 12:10 ` Willy Tarreau
0 siblings, 0 replies; 2+ messages in thread
From: Willy Tarreau @ 2017-05-27 12:10 UTC (permalink / raw)
To: Lars Erik Storbukås; +Cc: LKML
On Sat, May 27, 2017 at 02:08:01PM +0200, Lars Erik Storbukås wrote:
> I want to store the value of snd_cwnd when a congestion event occurs
> (value before snd_cwnd is reduced), and the new value of snd_cwnd (the
> value it has been reduced to). In other words: the congestion window
> before and after a congestion event occurs.
(...)
At the very least you should post this to netdev to get a useful response.
Willy
^ permalink raw reply [flat|nested] 2+ messages in thread
end of thread, other threads:[~2017-05-27 12:10 UTC | newest]
Thread overview: 2+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
2017-05-27 12:08 TCP get SND_CWND change on loss event Lars Erik Storbukås
2017-05-27 12:10 ` Willy Tarreau
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).