[openib-general] Re: LLTX and netif_stop_queue

[Eric Lemoine]

On 03 Jan 2005 10:04:21 -0500, jamal <hadi at cyberus.ca> wrote:
> this piece:
> -----
> +
> +                       /* And release queue */
> +                       spin_unlock(&dev->queue_lock);
>                 }
> ---------
> 
> Isnt there a possibility (higher as you increase number of processors)
> that you will spin for a long time in _the driver_ waiting for the queue
> lock?

I don't see how LLTX is different from non-LLTX wrt the time spent
spinning on queue_lock. What am i missing?

> 
> Maybe we need a flag "the queue lock" is already been grabbed passed
> to the driver. LLTX is a good  alias but insufficient (if you run your
> driver in an old kernels which support LLTX but not the idea of locking
> the queue for you).
> 
> Andi or anyone else - has anyone really done perfomance analysis of LLTX
> (with anything other than loopback) and shown it has any value? Maybe
> time to just shoot the damn thing.

I do not like LLTX too much either as I can't see a cleaner way to get
rid of that packet reordering race condition.

-- 
Eric