[ofa-general] Re: [PATCH 01/10] IB/ehca: Support for multiple event queues

[Hoang-Nam Nguyen]

Roland Dreier <rdreier at cisco.com> wrote on 16.07.2007 18:04:26:
> Do you have any data on how well this round-robin assignment works?
> It seems not quite right to me for the driver to advertise nr_eqs
> completion vectors, but then if round-robin is turned on to ignore the
> consumer's decision about which vector to use.
No, I've no figures to provide here. The background of this dist_eqs
option is actually to allow us testing across all event queues
without to change the testcases resp consumers to use certain
event queue number. Thus, I should comment it as EXPERIMENTAL?
> Maybe if round-robin is turned on you should report 0 as the number of
> completion vectors?  Or maybe we should allow well-known values for
> the completion vector passed to ib_create_cq to allow consumers to
> specify a policy (like round robin) instead of a particular vector?
> Maybe the whole interface is broken and we should only be exposing
> policies to consumers instead of the specific vector?
Agree in that device driver should not overwrite consumer's policy
of event queue assigment. Since dist_eqs is disabled as default,
there's no issue, isn't it?
Regarding ib_verbs: perhaps we should provide create/destroy_eq()
and let upper level protocols or consumers dictate the assignment
to cq by passing an event queue pointer to create_cq()...
> I think I would rather hold off on multiple EQs for this merge window
> and plan on having something really solid and thought-out for 2.6.24.
Fair enough. However why don't let us gather experience with this
feature now? Should we remove dist_eqs option for more consistency?
Thanks
Nam