netdev - Re: [net-next PATCH 1/3] net: make default tx_queue

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Message-ID: <20150813151033.048d73b8@redhat.com>
Date:	Thu, 13 Aug 2015 15:10:33 +0200
From:	Jesper Dangaard Brouer <brouer@...hat.com>
To:	Phil Sutter <phil@....cc>
Cc:	Alexei Starovoitov <alexei.starovoitov@...il.com>,
	netdev@...r.kernel.org, brouer@...hat.com
Subject: Re: [net-next PATCH 1/3] net: make default tx_queue_len
 configurable


On Thu, 13 Aug 2015 03:13:40 +0200 Phil Sutter <phil@....cc> 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
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