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[jason at jasonjgw.net]

After upgrading to the 2.6.29 kernel (the Debian packaged version), FreeSWITCH
takes up more CPU time than usual, e.g., 7% as reported by top, and the load
average is high (e.g., 0.87) even when the machine is idle and there are no
calls in progress. When top is run, FreeSWITCH appears at the start of the
list.

Is anybody else seeing this? The proportion of CPU time devoted to system
calls seems higher than it should be.

I would be interested in reports from anyone else who is running FreeSWITCH
under Linux 2.6.29.1 or equivalent from a distribution.


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[pawel at voiceworks.pl]

boot Your kernel with "divider=10 nohz=off" options

Recent kernels are tickless which basically causes all freeswitch timers/sleeps to fire at requested microsecond intervals.
With nohz kernels You get hundred times more system calls with freeswitch

On 2009-04-27, at 03:00, Jason White wrote:

[jason at jasonjgw.net]

Paweł Pierścionek <pawel@voiceworks.pl> wrote:

[jason at jasonjgw.net]

Just to add data to this:


PowerTOP 1.11 (C) 2007, 2008 Intel Corporation

Collecting data for 15 seconds


< Detailed C-state information is not available.>
P-states (frequencies)
2.34 Ghz 0.0%
2.00 Ghz 100.0%
Wakeups-from-idle per second : 405.4 interval: 15.0s
no ACPI power usage estimate available
Top causes for wakeups:
82.2% (1067.3) freeswitch : schedule_hrtimeout_range (hrtimer_wakeup)
[snip]


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[daniel at rimspace.net]

Paweł Pierścionek <pawel@voiceworks.pl>
writes:

G'day Paweł.

[pawel at voiceworks.pl]

Hi,

With really old kernels (100Hz) if You do sleep(1ms) You sleep for
10ms on average.
With enterprise kernels (250Hz) Your sleep resolution increases by a
factor of 4.
With fresh kernels (1000Hz) You get real 1ms timer resolution -
10fold increase compared to old kernels.

With tickless You get whatever resolution You want - eg when You
sleep for 100 microseconds(micro not mili) then You get exactly what
You wish for.

Now for reasons I do no try to understand there are a lot of
really short sleeps and fast timers in FreeSwitch - like 100
micro(1/10th of a ms).
So with CentOS such a 100 microsecond sleep cannot "fire" faster
then 250 times a second.
With tickless kernel same 100 microsecond sleep "fires" 10k times a
second.

Pawel,

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[brian at freeswitch.org]

Then it would be recommended to not do tickless clock

/b

On Apr 30, 2009, at 1:28 PM, Paweł Pierścionek wrote:

[mike at jerris.com]

Can you point out any place we do sub milli second sleeps? The timer
thread should be doing 1ms, I can't think of any that would be less.

MIke

On Apr 30, 2009, at 2:28 PM, Paweł Pierścionek wrote:

[pablosaro at gmail.com]

Jason:

IMHO, it is related with the following kernel options: CONFIG_HZ, CONFIG_NO_HZ and CONFIG_HIGH_RES_TIMERS.
Take a look at those options in your kernel and try modifying them until get the desired result. Google that options and you will find lots of discussions that will clarify your mind. Here you will find a simple explanation: http://www.smk.co.za/2007/07/21/a-tickless-kernel/
My configuration is 100 Hz + tickless + High-Res timers and everything goes perfect. When system is idle and FS has no calls, I see my CPU at 0%.
Hope it helps.

Pablo

On Thu, Apr 30, 2009 at 3:48 PM, Michael Jerris <mike@jerris.com (mike@jerris.com)> wrote:

[jason at jasonjgw.net]

Pablo Hernan Saro <pablosaro@gmail.com> wrote:

[kjv at ken-ton.com]

Folks;

Bear in mind that the frequency is (X)Hz * (num cores), hence saying 100Hz on a dual core winds up being 200Hz.


My setup is 250Hz on a Dual-Core and the quality is perfect.


Oh, btw folks, don't attempt to do anything involving QOS (be it TBF, CBQ, HTB, or whatnot) on anything less than kernel 2.6.28.4


I don't know why exactly that is, but extensive testing here in the lab showed that this was entirely FUBAR until 2.6.25.7 where it got better, but not perfect until 2.6.28.4
(I may not be exact on the revisions, but close enough...)


There's also some options in the kernel that you must disable (not compile in) if you expect packet shaping to work.


If there's interest in this, e-mail me directly and I'll see if I can toss it into the FS Wiki some time this upcoming weekend.



Best Regards,
Karl J. Vesterling
kjv@ken-ton.com (kjv@ken-ton.com)
202-461-3231 x0






On May 9, 2009, at 2:14 AM, Jason White wrote: