[ewg] Questions about CC in OFED

[Mascarenhas, Edward]

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

Intel's Fabric Manager User guide provides a brief section about enabling and using CCA. It can be downloaded from www.intel.com/infiniband. If you cannot download it, please contact me or our customer support offline and we can get you the manual and additional information about using CCA with PSM.

Basically there are configuration parameters in the Fabric Manager (FM) config file and there are PSM environment variable settings which can be modified. Once CCA is enabled in the FM config file, the fabric will use CCA since PSM has it enabled by default. The default values of PSM environment variables for CCA should be sufficient for most applications since we have taken care to find the best combination of parameters. If it becomes necessary to tune performance, additional PSM debug logging can be enabled to facilitate analysis of PSM CCA events.

- Edward
- -
- 

> -----Original Message-----
> From: ewg-bounces at lists.openfabrics.org [mailto:ewg-
> bounces at lists.openfabrics.org] On Behalf Of Ira Weiny
> Sent: Wednesday, June 27, 2012 9:26 AM
> To: Michael Zhang
> Cc: ewg at lists.openfabrics.org
> Subject: Re: [ewg] Questions about CC in OFED
> 
> 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
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