Re: [RFC PATCH 12/12] net: sched: pfifo_fast new option to deque multiple pkts

John Fastabend
2015-12-30T18:13:30Z

On 15-12-30 09:55 AM, John Fastabend wrote:
> Now that pfifo_fast is using the alf_queue data structures we can
> dequeue multiple skbs and save some overhead.
>
> This works because the bulk dequeue logic accepts skb lists already.
>
> Signed-off-by: John Fastabend <john.r.fastabend@intel.com>
> ---

oops I didn't mean to send this it obviously doesn't work because
until you have 8 skbs nothing gets dequeued. This was just a test
patch I was looking at for perf numbers. Maybe it provides some
insight into how we could build a pfifo_bulk or add an option to
pfifo_fast to dequeue multiple pkts at a time. The trick is to
sort out how long to wait for packets to build up or possibly
just remove this line,

+ if (this_cpu_ptr(qdisc->cpu_qstats)->qlen < 8)
+ return NULL;

And opportunistically pull packets out at the risk of over-running
the driver if those are large skbs.

.John