Re: [PATCH v2] Proportional Rate Reduction for TCP.

On Fri, 19 Aug 2011, Nandita Dukkipati wrote:

Forgot to turn off gmail's rich formatting, so re-sending to the list.

On Fri, Aug 19, 2011 at 3:25 AM, Ilpo Järvinen
[off-list ref] wrote:

quoted

On Fri, 19 Aug 2011, Nandita Dukkipati wrote:

quoted

+static void tcp_update_cwnd_in_recovery(struct sock *sk, int newly_acked_sacked,
+                                     int fast_rexmit, int flag)
+{
+     struct tcp_sock *tp = tcp_sk(sk);
+     int sndcnt = 0;
+     int delta = tp->snd_ssthresh - tcp_packets_in_flight(tp);
+
+     if (tcp_packets_in_flight(tp) > tp->snd_ssthresh) {
+             if (WARN_ON(!tp->prior_cwnd))
+                     tp->prior_cwnd = 1;

This should still be made larger to avoid problems if it ever will be
needed.

I am letting the value remain at 1, mainly because this is the valid
lowest non-zero value for snd_cwnd to take on. The main purpose of
this code is to catch any lurking bug outside of PRR which results in
an undesirable divide by 0 in PRR. I would like to fix that bug if I
find this code is executed.

NACK, until this value is at least 2 * tp->snd_ssthresh. Or alternatively 
the fallback is removed so that we DBZ and do not end up wrecking the 
network.

Other than that I'm ok with the patch (assuming the branches I brought
up earlier is ok for everybody else).


-- 
 i.