Re: [Qemu-devel] [Bug 899140] Re: Problem with Linux Kernel Traffic Control

[Vincent Autefage]

Here is the problem !

The Ubuntu version works only because it not uses an *Intel e1000* but a 
*rtl8139*.
Therefore, the problem about the e1000 is present in *all* version 
(original or ubuntu ones).

Thus, the file *e1000.c* must contain some instructions which imply the 
bad TC behavior.

Vincent

Le 15/12/2011 17:09, Stefan Hajnoczi a écrit :
> On Thu, Dec 15, 2011 at 3:03 PM, Vincent Autefage
> <address@hidden>  wrote:
>> Ok,
>>
>> So the e1000.c and the e1000_hw.h have absolutely no difference between
>> the original and the ubuntu version...
>> The only differences witch refers to the *Intel e1000* in the wall
>> sources is this one :
>>
>>
>> diff -ru qemu//hw/pc_piix.c qemu-kvm-0.14.0+noroms//hw/pc_piix.c
>> --- qemu//hw/pc_piix.c  2011-12-15 15:37:28.539290000 +0100
>> +++ qemu-kvm-0.14.0+noroms//hw/pc_piix.c        2011-02-22
>> 14:34:38.000000000 +0100
>>
>> @@ -123,7 +141,7 @@
>>           if (!pci_enabled || (nd->model&&  strcmp(nd->model,
>> "ne2k_isa") == 0))
>>               pc_init_ne2k_isa(nd);
>>           else
>> -            pci_nic_init_nofail(nd, "e1000", NULL);
>> +            pci_nic_init_nofail(nd, "rtl8139", NULL);
>>       }
>>
>>       if (drive_get_max_bus(IF_IDE)>= MAX_IDE_BUS) {
> That looks like it is only changing the default NIC from e1000 to
> rtl8139.
>
> Stefan
>

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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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