Re: [PATCH RFC 11/11] net/mlx5e: XDP TX xmit more

On Wed, 7 Sep 2016 19:57:19 +0300 Saeed Mahameed [off-list ref] wrote:

On Wed, Sep 7, 2016 at 6:32 PM, Eric Dumazet [off-list ref] wrote:

quoted

On Wed, 2016-09-07 at 18:08 +0300, Saeed Mahameed wrote:  

quoted

On Wed, Sep 7, 2016 at 5:41 PM, Eric Dumazet [off-list ref] wrote:  

quoted

On Wed, 2016-09-07 at 15:42 +0300, Saeed Mahameed wrote:  

[...]

quoted

Only if a qdisc is present and pressure is high enough.

But in a forwarding setup, we likely receive at a lower rate than the
NIC can transmit.

Yes, I can confirm this happens in my experiments.

quoted

Jesper has a similar Idea to make the qdisc think it is under
pressure, when the device TX ring is idle most of the time, i think
his idea can come in handy here. I am not fully involved in the
details, maybe he can elaborate more.

But if it works, it will be transparent to napi, and xmit more will
happen by design.

Yes. I have some ideas around getting more bulking going from the qdisc
layer, by having the drivers provide some feedback to the qdisc layer
indicating xmit_more should be possible.  This will be a topic at the
Network Performance Workshop[1] at NetDev 1.2, I have will hopefully
challenge people to come up with a good solution ;-)

-- 
Best regards,
  Jesper Dangaard Brouer
  MSc.CS, Principal Kernel Engineer at Red Hat
  Author of http://www.iptv-analyzer.org
  LinkedIn: http://www.linkedin.com/in/brouer

[1] http://netdevconf.org/1.2/session.html?jesper-performance-workshop