Re: Maximum size for memory registration (ibv_reg_mr)

Eli Cohen
2010-10-07T10:13:16Z

On Thu, Oct 07, 2010 at 11:40:02AM +0200, Or Gerlitz wrote:
> Roland Dreier wrote:
> >> max_mr_size returned by calling ibv_devinfo is 0xffffffffffffffff. Does this mean the size is unlimited?
> > It means that the query function might be returning bad data. What adapter is it?
>
> Yep, mlx4_ib_query_device does props->max_mr_size = ~0ull ...
>
> Jack, what would it take to fix that? I took a look and other settings are taken from
> dev->dev->caps.xxx where caps is of type mlx4_caps which is in turn filled @ drivers/net/mlx4/main.c
> :: mlx4_dev_cap I wasn't sure what field/computation would exactly account for later setting max_mr_size
>
It is not that trivial to calculate this value.
If you create a MR in kernel, it covers the entire address space and
the HCA does not pose any limit since you do not consume MTTs.
And if you use MTTs then the page size is a parameter in this
calculation - huge page, regular page etc.

Do leaving it as is seems to be the most accurate thing...