[ewg] Questions about CC in OFED

[Ira Weiny]

On Wed, 27 Jun 2012 11:41:03 +0800
Michael Zhang <ziwen1203 at gmail.com> wrote:

> Hi everybody,
> 
>   I focus on the source code of  IB congestion control in OFED, such as CCT
> related data structure and FECN/BECN process. But the only code related to
> the congestion control mechanism is found in the module of
> "infinipath-psm". As I know, psm works for MPI applications and actually I
> haven't installed psm in our system. I have done experiment through IPoIB
> and the congestion control still works that makes me confused.

I am not familiar with how psm may set CC parameters.  Perhaps someone from QLogic/Intel can speak up here?

>   Could someone tell me where is the CC-related source code located besides
> "infinipath-psm"? Or some functions are realized in hardware such as the
> movement of CCT Index when receives BECN message?
>   Thank you for your help!

The latest version of infiniband-diags (1.6.0)[*] has 2 tools (ibccquery and ibccconfig) which will allow one to query and set the CC parameters.  As you will note in the man page as well as the help output these tools are not to be used lightly.  You can cause instability in your fabric if you set things wrong.  However, when used properly they work well.

In addition, Al Chu from LLNL has posted a patch to OpenSM which allows for the setting of CC parameters in OpenSM.  Feedback from this patch has been minimal but Alex Netes (maintainer of OpenSM) says he will review it soon.  (http://www.spinics.net/lists/linux-rdma/msg11615.html)

Finally, if you are interested in the ongoing development of this and other features of Open Fabrics code you may want to sign up for the linux-rdma mailing list (linux-rdma at vger.kernel.org or http://vger.kernel.org/vger-lists.html).

Ira

[*] git://beany.openfabrics.org/~iraweiny/infiniband-diags.git

> 
> Best,
> Ziwen
> 
> -- 
> Ziwen(Michael) Zhang Ph.D candidate
> College of Computer
> National University of Defense Technology (NUDT) , P.R.China
> Email: ziwen at nudt.edu.cn ziwen1203 at gmail.com


-- 
Ira Weiny
Member of Technical Staff
Lawrence Livermore National Lab
925-423-8008
weiny2 at llnl.gov