[Freeswitch-users] KVM vs. XEN virtualization

Sergey Safarov s.safarov at gmail.com
Mon Apr 6 16:27:30 MSD 2015 

Errol can you test VM timer with utility
https://rt.wiki.kernel.org/index.php/Cyclictest

My VM currently have folowing results

[root at fs1 ~]#  date && /tmp/rt-tests/cyclictest -t42 -p 80 -d 0 -n -i
125 -l 240000 && date
Sun Apr  5 07:01:31 GMT 2015
# /dev/cpu_dma_latency set to 0us
policy: fifo: loadavg: 2.38 0.93 0.50 1/194 1574

T: 0 ( 1531) P:80 I:125 C: 240000 Min:      2 Act:   12 Avg:   16 Max:    1302
T: 1 ( 1532) P:80 I:125 C: 240000 Min:      2 Act:   15 Avg:   14 Max:    2895
T: 2 ( 1533) P:80 I:125 C: 240000 Min:      3 Act:   10 Avg:   12 Max:    2888
T: 3 ( 1534) P:80 I:125 C: 240000 Min:      1 Act:   16 Avg:   13 Max:    1333
T: 4 ( 1535) P:80 I:125 C: 240000 Min:      2 Act:   20 Avg:   14 Max:    2962
T: 5 ( 1536) P:80 I:125 C: 240000 Min:      1 Act:   12 Avg:   14 Max:    2946
T: 6 ( 1537) P:80 I:125 C: 240000 Min:      2 Act:   10 Avg:   13 Max:    1363
T: 7 ( 1538) P:80 I:125 C: 240000 Min:      2 Act:   12 Avg:   13 Max:    1344
T: 8 ( 1539) P:80 I:125 C: 240000 Min:      3 Act:   12 Avg:   16 Max:    1408
T: 9 ( 1540) P:80 I:125 C: 240000 Min:      1 Act:    8 Avg:   13 Max:    2882
T:10 ( 1541) P:80 I:125 C: 239974 Min:      2 Act:   12 Avg:   13 Max:    2908


On Mon, Apr 6, 2015 at 11:15 AM, Errol Samuels <ewsamuels at gmail.com> wrote:

> Good job and Thanks for sharing!
>
> KVM at digitalocean.com, Debian 7 64bit, FreeSWITCH 1.4.15: bad precision
>
>
> As someone who has been using KVM for a few years and has just migrated
> about 20 VMs across to Digital Ocean about 6 weeks ago I admit I am a
> little concerned about this finding.
>
> Just out of curiosity can you tell me the specs of the VM that you tested
> with and which DO Datacenter?  I am using NYC3 so perhaps and I will do
> some tests as soon as I have some time.
>
> With regards to Xen was this at Linode or inhouse?
>
> Thanks
>
> Errol
>
>
>
> On Sun, Apr 5, 2015 at 1:37 AM, Stanislav Sinyagin <ssinyagin at gmail.com>
> wrote:
>
>> here we go:
>>
>> https://txlab.wordpress.com/2015/04/05/testing-rtp-clock-precision-on-a-virtual-machine/
>>
>>
>>
>> On Sat, Apr 4, 2015 at 4:26 PM, Stanislav Sinyagin <ssinyagin at gmail.com>
>> wrote:
>> > On Sat, Apr 4, 2015 at 1:03 PM, Regis M <
>> regis.freeswitch.org at tornad.net> wrote:
>> >> How do you check wavs together in audacity ?
>> >
>> > you just open two WAV files, align their starting position, and
>> > visually check the waves. If there's a problem, you would see that
>> > after few seconds, the waves are not aligned any more.
>> >
>> >> Can you send me 2 samples wav (send... and recorded) so I could see
>> the 20ms
>> >> diff that you exposed...
>> >>
>> >> Is there a way to automate the result checking, so it could help to
>> monitor
>> >> itsp quality
>> >
>> > Here
>> > https://github.com/openpreserve/scape-xcorrsound/issues/17
>> > this is a link to a tool which compares two sound files at the wave
>> > level. You can also see the sound samples in the ticket.
>> > The problem is, that currently this tool does not detect such slipping
>> frames.
>> >
>> > I will also write a detailed article with examples, during the weekend.
>> >
>> >
>> >
>> >
>> >
>> >>
>> >>
>> >> 2015-04-04 12:53 GMT+02:00 Stanislav Sinyagin <ssinyagin at gmail.com>:
>> >>>
>> >>> Important is to send the media through two independent carriers -
>> then you
>> >>> can be sure that your clock is compared against a high quality one.
>> >>>
>> >>> On Apr 4, 2015 12:46 PM, "Regis M" <regis.freeswitch.org at tornad.net>
>> >>> wrote:
>> >>>>
>> >>>> Hi,
>> >>>>
>> >>>> It's a very interresting test and conclusion.
>> >>>>
>> >>>> I will try to build a similar environnement on my freeswitch to check
>> >>>> some system :)
>> >>>>
>> >>>> thanks
>> >>>>
>> >>>>
>> >>>>
>> >>>> 2015-04-04 2:16 GMT+02:00 Stanislav Sinyagin <ssinyagin at gmail.com>:
>> >>>>>
>> >>>>> hi,
>> >>>>>
>> >>>>> Here are some test results which might be interesting:
>> >>>>>
>> >>>>> I've set up a test FreeSWITCH server at digitalocean (they use KVM),
>> >>>>> and originated test calls to some ITSP accounts. Each call played a
>> >>>>> test sound file (voice samples from ITU:
>> >>>>>
>> http://www.itu.int/net/itu-t/sigdb/genaudio/AudioForm-g.aspx?val=1000050
>> >>>>> ), and on the receiving end another FreeSWITCH server was recording
>> >>>>> the received session. The receiving server was on a XEN VM. Both
>> >>>>> servers talked G711 to their corresponding ITSP accounts.
>> >>>>>
>> >>>>> Then I compared the source audio and received audio in Audacity
>> editor.
>> >>>>>
>> >>>>> The tests showed that the received voice wave shifts 20ms from the
>> >>>>> original sound every few seconds, randomly back and forward. This
>> >>>>> skewing was always present, regardless of ITSP and time of day.
>> >>>>>
>> >>>>> Then I moved the sending server to a XEN VM, and the waves appeared
>> >>>>> almost perfectly synchronized (there was a 5ms skew in one test,
>> and I
>> >>>>> guess it's related to transcoding buffer, as the sound was obviously
>> >>>>> transcoded).
>> >>>>>
>> >>>>> The effect was always visible with a 30-second sample, and I also
>> made
>> >>>>> additional tests with 2-minute samples.
>> >>>>>
>> >>>>> It would also be interesting to test this from a VmWare VM. If
>> someone
>> >>>>> wants to run such a test, feel free to contact me directly.
>> >>>>>
>> >>>>>
>> >>>>> cheers,
>> >>>>> stan
>> >>>>>
>> >>>>>
>> >>>>>
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>>
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>
>
> _________________________________________________________________________
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>
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