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[Qemu-devel] [Bug 899140] Re: Problem with Linux Kernel Traffic Control
From: |
Henrique Rodrigues |
Subject: |
[Qemu-devel] [Bug 899140] Re: Problem with Linux Kernel Traffic Control |
Date: |
Sun, 29 Jan 2012 04:49:01 -0000 |
Hi guys,
I'm having the same problem with a ubuntu 11.04 (natty) host. I tried to
set the rate controllers using tc both at the host and inside the guest
i.e.:
tc qdisc add vnic0 root tbf rate 20mbit burst 20480 latency 50ms (host - to
control the traffic going to the guest vm) and
tc qdisc add eth0 root tbf rate 20mbit burst 20480 latency 50ms (guest)
And the results are the same reported initially: ~140kbit/sec. I also
tried to use policing filters at the host but I got the same results.
However, if I use htb I can get reasonable throughputs (~20mbit). I used
these commands (both for host and guest):
tc qdisc add dev <DEV> root handle 1: htb default 255
tc class add dev <DEV> parent 1: classid 1:1 htb rate 20mbit burst 20480
tc filter add dev <DEV> parent 1: prio 255 proto ip u32 match ip src 0.0.0.0/0
flowid 1:1
It seems that the problem is related with the root qdisc only. Have you
guys found an answer for this?
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https://bugs.launchpad.net/bugs/899140
Title:
Problem with Linux Kernel Traffic Control
Status in QEMU:
New
Bug description:
Hi,
The last main versions of QEMU (0.14.1, 0.15 and 1.0) have an important
problem when running on a Linux distribution which running itself a Traffic
Control (TC) instance.
Indeed, when TC is configured with a Token Bucket Filter (TBF) with a
particular rate, the effective rate is very slower than the desired one.
For instance, lets consider the following configuration :
# tc qdisc add dev eth0 root tbf rate 20mbit burst 20k latency 50ms
The effective rate will be about 100kbit/s ! (verified with iperf)
I've encountered this problem on versions 0.14.1, 0.15 and 1.0 but not with
the 0.14.0...
In the 0.14.0, we have a rate of 19.2 mbit/s which is quiet normal.
I've done the experimentation on several hosts :
- Debian 32bit core i7, 4GB RAM
- Debian 64bit core i7, 8GB RAM
- 3 different high performance servers : Ubuntu 64 bits, 48 AMD Opteron,
128GB of RAM
The problem is always the same... The problem is also seen with a
Class Based Queuing (CBQ) in TC.
Thanks
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- [Qemu-devel] [Bug 899140] Re: Problem with Linux Kernel Traffic Control,
Henrique Rodrigues <=