net.inet.tcp.slowstart_flightsize in 8-STABLE

[Kostik Belousov]

On Fri, Nov 12, 2010 at 09:21:29PM +1100, Lawrence Stewart wrote:
> On 11/12/10 20:44, Lawrence Stewart wrote:
> > On 11/07/10 17:32, Lawrence Stewart wrote:
> >> On 11/03/10 09:30, Andre Oppermann wrote:
> >>> On 02.11.2010 01:11, Maxim Dounin wrote:
> >>>> Hello!
> >>>>
> >>>> On Mon, Sep 27, 2010 at 03:17:59PM +0200, Andre Oppermann wrote:
> >>>>
> >>>>> On 27.09.2010 10:12, Maxim Dounin wrote:
> >>>>>> Hello!
> >>>>>>
> >>>>>> On Mon, Sep 13, 2010 at 09:24:53PM +0400, Maxim Dounin wrote:
> >>>>>>
> >>>>>> [...]
> >>>>>>
> >>>>>>> Andre, could you please take a look at one more patch as well?
> >>>>>>>
> >>>>>>> Igor reported that it still sees 100ms delays with rfc3465 turned
> >>>>>>> on, and it turns out to be similar issue (setting cwnd to 1*MSS)
> >>>>>>> for hosts found in hostcache.
> >>>>>>>
> >>>>>>> The problem with setting cwnd from hostcache was already reported
> >>>>>>> here:
> >>>>>>>
> >>>>>>> http://www.freebsd.org/cgi/query-pr.cgi?pr=kern/92690
> >>>>>>> http://lists.freebsd.org/pipermail/freebsd-net/2007-July/014780.html
> >>>>>>>
> >>>>>>> As using larger cwnd from hostcache may cause problems on
> >>>>>>> congested links (see second thread) I changed code to only use
> >>>>>>> cached cwnd as an upper bound for cwnd (instead of fixing current
> >>>>>>> code).  This is also in-line with what we do on connection
> >>>>>>> restarts.
> >>>>>>>
> >>>>>>> We may later consider re-adding usage of larger cwnd from
> >>>>>>> hostcache.  But I believe it should be done carefully and
> >>>>>>> probably behind sysctl, off by default.
> >>>>>>
> >>>>>> Ping.
> >>>>>
> >>>>> Thanks for the reminder.  I'll disable priming CWND from hostcache.
> >>>>
> >>>> Ping again.
> >>>>
> >>>> I would like to see the patch in question[1] committed and MFC'ed
> >>>> somewhere before 8.2.
> >>>>
> >>>> Andre, if you are just too busy to do it yourself - please say so,
> >>>> I'll ask somebody else to commit it.
> >>>
> >>> Thanks for the reminder.  After EuroBSDCon Developer Summit I was
> >>> busy with other work and most of my tcp work was stalled due to
> >>> review bandwidth issues.
> >>
> >> Sorry for the review bandwidth issues. I'm only just managing to keep my
> >> head above water at the moment and have had to reduce much of my FreeBSD
> >> work to a trickle.
> >>
> >>> Lawrence, could you please spare a few seconds and take a quick look
> >>> at the attached patch?
> >>
> >> The patch looks fine, please commit. I hope to give the hostcache some
> >> TLC at some point, but in the meantime it's fine to ignore cached cwnd.
> > 
> > FYI Andre, this patch got rolled into r215166 because I had to move all
> > the code around which the patch was based on. Is that going to cause any
> > issues here? I should have checked prior to committing but completely
> > forgot I had pulled the patch into my dev tree before creating the mod
> > CC patch.
> 
> Gah, I think I've answered my own question. MFCing the patch standalone
> in time for 8.2 as Maxim requested is not going to be possible. I think
> I'll have to back out r215166, commit your patch and then recommit the
> modular CC patch.
> 
> Unless someone can think of a way that doesn't involve all the mucking
> about?
Well, if the change is indeed already in HEAD, you can do a direct commit
to stable/8 after proper MFC period, noting that this is a cherry-pick of
the part of corresponding revision.
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