Subject: Re: [net-next PATCH 1/3] net: make default tx_queue_len configurable

From: Jesper Dangaard Brouer <[email-masked]>
Date: Thu, 13 Aug 2015 15:10:33 +0200

On Thu, 13 Aug 2015 03:13:40 +0200 Phil Sutter <[email-masked]> wrote:

> On Tue, Aug 11, 2015 at 06:13:49PM -0700, Alexei Starovoitov wrote:

> > In general 'changing the default' may be an acceptable thing, but then
> > it needs to strongly justified. How much performance does it bring?
> 
> A quick test on my local VM with veth and netperf (netserver and veth
> peer in different netns) I see an increase of about 5% of throughput
> when using noqueue instead of the default pfifo_fast.

Good that you can show 5% improvement with a single netperf flow.  We
are saving approx 6 atomic operations avoiding the qdisc code path.

This fixes a scalability issue with veth. Thus, the real performance
boost will happen with multiple flows and multiple CPU cores in
action.  You can try with a multi core VM and use super_netperf.

https://github.com/borkmann/stuff/blob/master/super_netperf

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