net.inet.tcp.slowstart_flightsize in 8-STABLE

Lawrence Stewart lstewart at freebsd.org
Fri Nov 12 10:21:32 UTC 2010


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?

Cheers,
Lawrence


More information about the freebsd-net mailing list