[ofa-general] Setting the Credits.

[Ashwath Narasimhan]

Hi Jason/All,Thank you for your response. Do you mean the link layer flow
control (VL's)? or the end to end flow control credits of the Transport
layer? How do I set the end to end flow control credits? I looked at the
driver source code and the file ipath_qp.c interested me. Here they
calculate the credits based on the difference between the head and tail
pointers of the 'qp' receive queue pairs (refer -
drivers/infiniband/hw/ipath). should i change the size of these queues? am I
even looking at the right file?

regards,
Ashwath.

On Thu, Aug 6, 2009 at 5:12 PM, Jason Gunthorpe <
jgunthorpe at obsidianresearch.com> wrote:

> On Wed, Aug 05, 2009 at 08:03:04PM -0400, Ashwath Narasimhan wrote:
>
> > The reason why I need such small rates is because I interface the
> > Infiniband HCA to an FPGA via an Infiniband physical link.  Imagine
> > the FPGA as a simple repeater that simply forwards the infiniband
> > signals to the Target HCA. The FPGA cannot handle such a high data
> > rate and neither do I have as much memory as required to buffer it
> > on the FPGA (I might drop packets if the buffer becomes full). Hence
> > I wish to limit the rate to say 100Mbps instead of 2.5Gbps.
>
> The correct thing to do is manage the flow control credits you are
> giving to the IB network so you don't loose packets.
>
> Jason
>



-- 
regards,
Ashwath
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