Basics of congestion control?

Basics of congestion control?

[Sebastian Riemer]

Hi all,

could someone please explain what I can do with the new congestion control?

Do I understand it right that I can influence the flow control (e.g.
amount of credits) with it so that I can avoid disruption (XmitWait,
XmitDiscardedPackets) caused by congestion?

This is at least what we need. ;-)

Cheers,
Sebastian

-- 
Sebastian Riemer
Linux Kernel Developer

ProfitBricks GmbH • Greifswalder Str. 207 • 10405 Berlin, Germany
www.profitbricks.com • sebastian.riemer-EIkl63zCoXaH+58JC4qpiA@public.gmane.org
Tel.: +49 - 30 - 60 98 56 991 - 915

Sitz der Gesellschaft: Berlin
Registergericht: Amtsgericht Charlottenburg, HRB 125506 B
Geschäftsführer: Andreas Gauger, Achim Weiss

--
To unsubscribe from this list: send the line "unsubscribe linux-rdma" in
the body of a message to majordomo-u79uwXL29TY76Z2rM5mHXA@public.gmane.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html

Re: Basics of congestion control?

[Alex Netes]

Hi Sebastian,

On 11:37 Tue 31 Jul     , Sebastian Riemer wrote:
> Hi all,
> 
> could someone please explain what I can do with the new congestion control?
> 
> Do I understand it right that I can influence the flow control (e.g.
> amount of credits) with it so that I can avoid disruption (XmitWait,
> XmitDiscardedPackets) caused by congestion?

Congestion control isn't a credit based mechanism. While InfiniBand flow
control is defined between two ports of the same link, congestion control is
working across the fabric between a congestion point (a switch) and a reaction
point (source node). Reaction point implements a Congestion Control Table that
contains an array of values of injection rate delay used to control
congestion. You can find more information in the IBTA LWG Errata document
3Q2010.

-- Alex
--
To unsubscribe from this list: send the line "unsubscribe linux-rdma" in
the body of a message to majordomo-u79uwXL29TY76Z2rM5mHXA@public.gmane.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html

Re: Basics of congestion control?

[Sebastian Riemer]

On 31.07.2012 13:08, Alex Netes wrote:
> Congestion control isn't a credit based mechanism. While InfiniBand flow
> control is defined between two ports of the same link, congestion control is
> working across the fabric between a congestion point (a switch) and a reaction
> point (source node). Reaction point implements a Congestion Control Table that
> contains an array of values of injection rate delay used to control
> congestion. You can find more information in the IBTA LWG Errata document
> 3Q2010.

Nice, thank you very much!

I've found the IBTA spec and the errata.

Cheers,
Sebastian
--
To unsubscribe from this list: send the line "unsubscribe linux-rdma" in
the body of a message to majordomo-u79uwXL29TY76Z2rM5mHXA@public.gmane.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html