netdev - Re: [PATCH net 1/5] tcp_bbr: cut pacing rate only if filled pipe

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Message-ID: <20170714161535.66c5110a@xeon-e3>
Date:   Fri, 14 Jul 2017 16:15:35 -0700
From:   Stephen Hemminger <stephen@...workplumber.org>
To:     Neal Cardwell <ncardwell@...gle.com>
Cc:     David Miller <davem@...emloft.net>,
        Netdev <netdev@...r.kernel.org>,
        Yuchung Cheng <ycheng@...gle.com>,
        Soheil Hassas Yeganeh <soheil@...gle.com>
Subject: Re: [PATCH net 1/5] tcp_bbr: cut pacing rate only if filled pipe

On Fri, 14 Jul 2017 18:54:02 -0400
Neal Cardwell <ncardwell@...gle.com> wrote:

> On Fri, Jul 14, 2017 at 6:36 PM, Stephen Hemminger
> <stephen@...workplumber.org> wrote:
> > On Fri, 14 Jul 2017 17:49:21 -0400
> > Neal Cardwell <ncardwell@...gle.com> wrote:
> >  
> >> In bbr_set_pacing_rate(), which decides whether to cut the pacing
> >> rate, there was some code that considered exiting STARTUP to be
> >> equivalent to the notion of filling the pipe (i.e.,
> >> bbr_full_bw_reached()). Specifically, as the code was structured,
> >> exiting STARTUP and going into PROBE_RTT could cause us to cut the
> >> pacing rate down to something silly and low, based on whatever
> >> bandwidth samples we've had so far, when it's possible that all of
> >> them have been small app-limited bandwidth samples that are not
> >> representative of the bandwidth available in the path. (The code was
> >> correct at the time it was written, but the state machine changed
> >> without this spot being adjusted correspondingly.)
> >>
> >> Fixes: 0f8782ea1497 ("tcp_bbr: add BBR congestion control")
> >> Signed-off-by: Neal Cardwell <ncardwell@...gle.com>
> >> Signed-off-by: Yuchung Cheng <ycheng@...gle.com>
> >> Signed-off-by: Soheil Hassas Yeganeh <soheil@...gle.com>  
> >

You are correct, these look more like bug fixes. I was a little concerned
that the changes would be visible but they really aren't user visible.

Should they go to stable as well?