Re: [PATCH rdma-next 0/4] Add packet pacing support for IB verbs

[Leon Romanovsky <leon-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org>]

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On Wed, Nov 09, 2016 at 05:06:52PM +0000, Hefty, Sean wrote:
> > On Tue, Nov 08, 2016 at 05:49:26PM +0000, Hefty, Sean wrote:
> > > > When sending from a 10G host to a 1G host, it is easy to overrun
> > the
> > > > receiver,
> > > > leading to packet loss and traffic backing off. Similar problems
> > occur
> > > > when
> > > > a 10G host sends data to a sub-10G virtual circuit, or a 40G host
> > > > sending
> > > > to a 10G host. Packet pacing could control packet injection rate
> > and
> > > > reduces
> > > > network congestion to maximize throughput & minimize network
> > latency.
> > >
> > > Why isn't the path record data and existing mechanisms sufficient to
> > handle this?
> > >
> >
> > Packet pacing allows different combinations of traffic shaping: per-
> > CPU,
> > per-flow and their combinations with better and steady QoS requirements
> > without involving subnet management.
>
> The patch adds this as a QP attribute, and we already have a rate for that.  I still don't see why the standard mechanisms are insufficient or couldn't be adapted.

I'll let to Bodong to elaborate on it more, but as far as I see, the AH
attribute is relevant to UD QP only, while the packet pacing is intended
for all types of QPs.

Thanks

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