[openib-general] Re: [PATCH] TX/RX_RING_SIZE as loadable parameters

[Michael S. Tsirkin]

Quoting r. Roland Dreier <rdreier at cisco.com>:
> Subject: Re: [PATCH] TX/RX_RING_SIZE as loadable parameters
> 
>     Thomas> Sorry but that sounds like a needless restriction. Some
>     Thomas> hardware doesn't have ring buffers at all. Well, if ipoib
>     Thomas> does it this way though, I guess that's what it is.
> 
> It's a property of the way the ipoib driver keeps track of outstanding
> work requests.  We just keep constantly-incrementing head and tail
> pointers to a circular buffer, and mask them down to get an index into
> the actual buffer.

Looks like its already creating user confusion :)
I think, we could easily implement resize QP if we add a requirement
that it is only done on QP in RESET state.

Then, we could sample txqueuelen on interface up and set TX size
appropriately.
The user will be then responsible for tuning this parameter.

Makes sense?

-- 
Michael S. Tsirkin
Staff Engineer, Mellanox Technologies