[PATCH 3/3] net: hisilicon: new hip04 ethernet driver

David Laight
2014-03-26T09:55:46Z

From: Arnd Bergmann
> On Tuesday 25 March 2014 10:16:28 Florian Fainelli wrote:
> >
> > Ok, well that's really unfortunate, to achieve the best of everything,
> > the workaround should probably look like:
> >
> > - keep reclaiming TX buffers in ndo_start_xmit() in case you push more
> > packets to the NICs than your timer can free
> > - reclaim TX buffers in NAPI poll() context for "symetrical" workloads
> > where e.g: TCP ACKs received allow you to complete TX buffers
> > - have a timer like you suggest which should help with transmit only
> > workloads at a slow rate
>
> Yes, that is what I was thinking, but with orphaning the tx skbs,
> we can probably be a little smarter. Note that in order to check
> the state of the queue, we have to do a read from uncached memory,
> since the hardware also doesn't support cache coherent DMA.
> We don't want to do that too often.

Possibly you can check for all the pending transmits having
completed - the most likely case. Instead of checking them
individually?

You should limit the number of tx bytes as well as the number
of tx frames - buffering a ring full of large frames subverts
some of the algorithms higher up the stack.

David