netdev - Re: Disabling XPS for 4.4.0-1+ixgbe+OpenStack VM over a VLAN means 65% increase in netperf TCP

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Date:	Mon, 8 Feb 2016 10:03:35 -0800
From:	Rick Jones <rick.jones2@....com>
To:	Tom Herbert <tom@...bertland.com>
Cc:	Linux Kernel Network Developers <netdev@...r.kernel.org>
Subject: Re: Disabling XPS for 4.4.0-1+ixgbe+OpenStack VM over a VLAN means
 65% increase in netperf TCP_STREAM

On 02/04/2016 11:38 AM, Tom Herbert wrote:
> I'd start with verifying the XPS configuration is sane and then trying
> to reproduce the issue outside of using VMs, if both of those are okay
> then maybe look at some sort of bad interaction with OpenStack
> configuration.

So, looking at bare-iron, I can see something similar but not to the 
same degree (well, depending on which is one's metric of interest I guess):


XPS being enabled for ixgbe here looks to be increasing receive side 
service demand by 30% but there is enough CPU available in this setup 
that it is only a loss of 2.5% or so on throughput.

stack@...erf-cp1-comp0001-mgmt:~$ grep 87380 xps_on_* | awk 
'{t+=$6;r+=$9;s+=$10}END{print "throughput",t/NR,"recv sd",r/NR,"send 
sd",s/NR}'
throughput 9072.52 recv sd 0.8623 send sd 0.3686
stack@...erf-cp1-comp0001-mgmt:~$ grep TCPOFO xps_on_* | awk '{sum += 
$NF}END{print "sum",sum/NR}'
sum 1621.1
stack@...erf-cp1-comp0001-mgmt:~$ grep 87380 xps_off_* | awk 
'{t+=$6;r+=$9;s+=$10}END{print "throughput",t/NR,"recv sd",r/NR,"send 
sd",s/NR}'
throughput 9300.48 recv sd 0.6543 send sd 0.3606
stack@...erf-cp1-comp0001-mgmt:~$ grep TCPOFO xps_off_* | awk '{sum += 
$NF}END{print "sum",sum/NR}'
sum 173.9

happy benchmarking,

rick jones

raw results at ftp://ftp.netperf.org/xps_4.4.0-1_ixgbe.tgz