[Xen-devel] Perf regression of netperf compared Xen 4.4 to origin/master

[Konrad Rzeszutek Wilk <konrad.wilk@xxxxxxxxxx>]

The test is pretty silly.

I've 14 guests, and I make each guest run netperf against the other.
I start with 1 pair, then 2 pairs, then up to 7. Each guest
is 768 MB, runs in a RAMdisk and just has one vif. The box is
a SuperMicro X8DB8+ with two E5520 and 12GB of RAM.
The netperf runs for a minute. The guests are PVHVM and I am
using qemu-upstream.  The guest configs are:

builder='hvm'
disk = [ 'file:/mnt/lab/bootstrap-x86_64/root_image.iso,hdc:cdrom,r']
memory=768
boot='d'
vcpus=1
serial='file:/var/log/xen/console-g-vm0.log'
vnclisten='0.0.0.0'
name='g-vm0'
on_crash='preserve'
# IP is 192.168.102.90
vif = [ 'mac=00:0f:4b:01:01:00, bridge=switch' ]
.. and naturally the ip, name and MAC change for each guest.

The kernel for both the guest and domain 0 is the same - no
configuration change. The Xen is built without debug=y.

When doing this test under Xen 4.4:

 0,  8823.14,  8823.14,  8823.14,  8823.14
 1,  9645.67,  4822.84,  4085.88,  5559.79
 2,  11725.3,  3908.44,  2652.09,  4698.15
 3,  12199.3,  3049.83,  1473.95,  3631.93
 4,  12223.2,  2444.64,  1023.48,  2887.83
 5,  11733.4,  1955.57,   909.66,  3057.11
 6,  11927.7,  1703.95,  1187.29,  1933.76
 7,  11623.8,  1452.97,   538.11,  2228.21

And when doing it under 'master' branch:


 0,  8478.57,  8478.57,  8478.57,  8478.57
 1,  7663.38,  3831.69,  3427.70,  4235.68
 2,  8381.77,  2793.92,  1977.75,  3242.46
 3,  8165.55,  2041.39,  1373.43,  2294.48
 4,  7742.64,  1548.53,   763.08,  2065.43
 5,  7691.87,  1281.98,   626.85,  1784.72
 6,  8337.06,  1191.01,   626.98,  1847.55
 7,   8074.8,  1009.35,   384.84,  1380.00

I am going to start a bit of git bisection to figure this out
but if somebody has some ideas on where/when to concentrate I
would appreciate the help.

Attachment: network.png
Description: PNG image

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