[openib-general] [PATCH] mthca updates (2.6.8 dependent)

[Michael S. Tsirkin]

Hello!
Quoting r. Roland Dreier (roland at topspin.com) "Re: [openib-general] [PATCH] mthca updates (2.6.8 dependent)":
>     Dror> Anyway, I believe that with both MSI and MSI-X you can avoid
>     Dror> the PIO read. * If it's MSI-X, it's easy. By the IRQ# you
>     Dror> can tell which EQ has work.  * If it's MSI, just go and peek
>     Dror> into all available EQs. It's much more efficient than doing
>     Dror> a PIO read.
> 
> It seems this would apply to standard INTx mode as well.  Do you know
> why Mellanox didn't use this in THCA?  In any case, I'll have to
> benchmark this approach.

It does apply to the standard INTx mode. However with standard
INTx mode there is more of a chance that by the time you peek
the EQ, the EQ is empty and you end up getting an extra interrupt.
    
But please note that you must arm all EQs even if you dont find
any EQ entries there.
So you trade PIO read for PIO writes, and the more EQs the more
writes you will need.

I dont know what the driver currently does but it is certainly
something we planned to do.

MST