[ofa-general] Re: [PATCH RFC] sharing userspace IB objects

[Or Gerlitz]

Michael S. Tsirkin wrote:
>> Quoting Roland Dreier <rdreier at cisco.com>:
>> Subject: Re: [PATCH RFC] sharing userspace IB objects

>>    Is there really a strong use case for making every type of object
>>    shareable?  Can we handle the SRC stuff without going to this
>>    extreme of complexity?

> This is not directly related to SRC: this is an effort
> to make it possible to share QPs, CQ etc across processes
> in the same way as they can be currently shared across threads.
> So assuming that we want multiple processes to post to
> the same QP, how can we support this?

Indeed, lets zoom out a little and define the high level scope and 
design here, such that people can comment.

For example the design should treat also sharing/passing the CM 
(RDMA-CM) ID among processes, and state the limitations, eg on the 
private data etc.

>>  - Given that everything shared is in shared memory,

> I think we should try and keep shared memory usage to minimum.
> For example, in mthca mr object just needs a key: we could
> keep it in non-shared memory, just pass the key around
> and save on sahred memory usage.

what do you refer by "it" here? is it the lkey of the memory used for 
the QP, or the lkey describing the rx/tx buffers?

On the latter case, looking on ib_umem_get, it uses current->mm etc,
doesn't this mean that there should be some difference between shared to 
non shared memory?

Or.