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Problem with Linux Kernel Traffic Control
Hi,
The two last main versions of QEMU (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 0.15 and 1.0 but not with the 0.14...
In the 0.14, 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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