net.inet.tcp.slowstart_flightsize in 8-STABLE

[Lawrence Stewart]

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.

Cheers,
Lawrence