[openib-general] Serialization in ib_uverbs

[Boyd R. Faulkner]

On Mon June 5 2006 15:36, Roland Dreier wrote:
>     Boyd> I have a question about the intent of the mutex lock
>     Boyd> ib_uverbs_idr_mutex used in kernel interface from user
>     Boyd> libraries.  It appears to be a lock on the idr linked lists
>     Boyd> but as a great many, if not all, of the ib_uverbs commands
>     Boyd> grab the mutex at the start of the function and hold it to
>     Boyd> the end, it acts to serialize all the library accesses to
>     Boyd> the kernel.  Is this intended?
>
> Yes, when I first implemented things it made things a lot easier to
> serialize things.  For example holding the mutex during the entire
> process of creating a QP prevents the associated CQs from being
> destroyed in the middle of the operation.
>
> It does seem to be a scalability problem for some devices/workloads,
> and Robert Walsh from qlogic was planning on looking at this
> (replacing the mutex with a reference counting scheme).  I don't know
> if he's started on this or not.
>
>  - R.

It is in the pipe.  Sweet.

Thanks,
Boyd

-- 
Boyd R. Faulkner
Open Grid Computing, Inc.
Phone:	512-343-9196 x109
Fax:	512-343-5450