[Openib-windows] Adding an environment variable for determining the initial CQ size

[Fabian Tillier]

Hi Tzachi,

On 7/13/06, Tzachi Dar <tzachid at mellanox.co.il> wrote:
> Fab,
>
> We do plan to add resize CQ support but since it is quite a large  and
> risky patch we prefer not to do that before the coming release.
> The WSD provider implementation will open another CQ in case there is no
> more place available and will not free the CQ if it is empty we may get
> to a leakage scenario. A larger CQ helps to reduce this. There is no
> limitation for large cluster other then this possible leakage.

It's not really a leak, as the CQ is tracked - it just means a CQ is
allocated, and its thread is in a wait state.  I want to be careful
about the language here as calling it a leak makes it sound like a
bug, whereas it is not.

> Once again, we will defiantly add resize CQ to MTHCA but I doubt if it
> will be ready for the coming release.

Right, understood.  I don't think we should delay the coming release
to add resize_cq support.

> Each CQE entry is 32B. This mean that the memory allocated per CQ is 32
> * 512 * 32 = 512KB

Would you mind just changing the initial CQ size to 500, without
adding the environment variable?  This would reduce the number of CQs
and associated threads in large runs.

I don't really want to add a tunable for this as users are unlikely to
know how to properly use this variable, and it is going to be short
lived anyhow.

Thoughts?

- Fab