[Bug 1862044] [NEW] packet loss, extra latency and lower bandwidth on bionic

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We are investigating migrating our servers from Xenial to Bionic.
We are seeing significant network differences between the 2 LTS versions.
Using the same hardware an machines connected to a single swith on the same network, we see:
10% less packets throuput on bionic in comparision to Xenial when running uperf.
Also "tc -s qdisc" report packets been dropped on Bionic but not Xenial.
The command iperf -c <host> -u -d -p 20 timeout on Bionic and not on Xenial, and if you reduce the value of p, you will see more packet drops on Bionic.

We tryied to upgrade the xenial kernel to the same version than bionic.
We did not see any improvement.

All the tests are performed with 4 identical physical machines connected
to the same physical switch. With one bionic machine, one Xenial machine
and 2 extra Xenial machine that act as iperf/uperf clients.

All 4 nodes are configured as ntp peers with each others. Under load,
the bionic machine see siginificant jitter improvement with the 3 others
machines. We don't see that with the Xenial hosts.

I doesn't seems to be an hardware compatibility issue as we see
significant network performance loss in our datacenter on fully
different hardware.

ProblemType: Bug
DistroRelease: Ubuntu 18.04
Package: iperf 2.0.10+dfsg1-1ubuntu0.18.04.2
ProcVersionSignature: Ubuntu 4.15.0-76.86-lowlatency 4.15.18
Uname: Linux 4.15.0-76-lowlatency x86_64
ApportVersion: 2.20.9-0ubuntu7.9
Architecture: amd64
Date: Wed Feb 5 17:14:25 2020
Dependencies:
 gcc-8-base 8.3.0-6ubuntu1~18.04.1
 libc6 2.27-3ubuntu1
 libgcc1 1:8.3.0-6ubuntu1~18.04.1
 libstdc++6 8.3.0-6ubuntu1~18.04.1
InstallationDate: Installed on 2020-01-29 (7 days ago)
InstallationMedia: Ubuntu-Server 18.04.3 LTS "Bionic Beaver" - Release amd64 (20190805)
ProcEnviron:
 TERM=xterm-256color
 PATH=(custom, no user)
 XDG_RUNTIME_DIR=<set>
 LANG=en_US.UTF-8
 SHELL=/bin/bash
SourcePackage: iperf
UpgradeStatus: No upgrade log present (probably fresh install)

ProblemType: Bug
DistroRelease: Ubuntu 18.04
Package: systemd 237-3ubuntu10.29
ProcVersionSignature: Ubuntu 4.15.0-76.86-lowlatency 4.15.18
Uname: Linux 4.15.0-76-lowlatency x86_64
ApportVersion: 2.20.9-0ubuntu7.9
Architecture: amd64
Date: Wed Feb  5 17:29:53 2020
ExecutablePath: /lib/systemd/systemd
InstallationDate: Installed on 2020-01-29 (7 days ago)
InstallationMedia: Ubuntu-Server 18.04.3 LTS "Bionic Beaver" - Release amd64 (20190805)
MachineType: Dell Inc. XPS 8700
ProcEnviron:
 TERM=linux
 PATH=(custom, no user)
ProcKernelCmdLine: BOOT_IMAGE=/vmlinuz-4.15.0-76-lowlatency root=UUID=400563c9-8749-47b7-8abb-1efdb57bc589 ro
SourcePackage: systemd
UpgradeStatus: No upgrade log present (probably fresh install)
dmi.bios.date: 05/16/2013
dmi.bios.vendor: Dell Inc.
dmi.bios.version: A01
dmi.board.name: 0KWVT8
dmi.board.vendor: Dell Inc.
dmi.board.version: A00
dmi.chassis.type: 3
dmi.chassis.vendor: Dell Inc.
dmi.modalias: dmi:bvnDellInc.:bvrA01:bd05/16/2013:svnDellInc.:pnXPS8700:pvr:rvnDellInc.:rn0KWVT8:rvrA00:cvnDellInc.:ct3:cvr:
dmi.product.family: To be filled by O.E.M.
dmi.product.name: XPS 8700
dmi.sys.vendor: Dell Inc.

** Affects: systemd (Ubuntu)
     Importance: Undecided
         Status: New


** Tags: amd64 apport-bug bionic uec-images
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packet loss, extra latency and lower bandwidth on bionic
https://bugs.launchpad.net/bugs/1862044
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