[Freeswitch-users] Choppy sound with PCMU

Mon Dec 7 09:32:25 PST 2009

oh and also

use top -H to see which threads are using specific CPU and try to cross
reference them by attaching with gdb and dumping all the thread bt

On Mon, Dec 7, 2009 at 10:16 AM, Michael Jerris <mike at jerris.com> wrote:

> Also I have seen some people reporting that the new tickless timers in
> newer kernels work better.  You may want to try those.
>
> Mike
>
> On Dec 7, 2009, at 11:00 AM, Anthony Minessale wrote:
>
> Did you do each thing alone too to tell the difference?
> -hp alone, disable monotonic alone (i did not see you mention the disable
> monotonic)
>
> as for your 4ms thing, yes we require high resolution timing, if we ask to
> sleep 1000 microseconds that is what we need it to sleep for or at least as
> close as possible, and the main reason that thread is never sleeping is
> because you can't actually count on it to run every 1ms but you mostly can.
> Hence the whole philosophy on only making 1 thread run hot all the time to
> ensure that the rest don't have to repeat the same algorithm.  We focus on
> high end performance this was the point of your experimentation because we
> will need to use a compile time defines and other logic to make it more
> efficient on your platform, a platform which we are not using.  I am curious
> what would happen if you install Kristian's astlinux on one of your devices,
> i think you should also compare the kernel versions.
>
>
> What OS are you running anyway?
>
> Here are some more things to try (running plain trunk with no mods) do
> these systematically each alone and all together with/without -hp or disable
> monotonic etc to see what different combos create
>
> comment out this line (line 10)
> #define DISABLE_1MS_COND
>
> rebuild, this tells it to run a conditional at 1ms in the same timer thread
> which will make all the switch_cond_next share a 1ms conditional instead of
> doing microsleeps
>
> next
>
> some kernels/devices work better using select(0) for sleep where others
> work better using usleep.
> comment out line 109
> apr_sleep(t);
>
> and try
> usleep(t)
>
> also mac works better using nanosleep so you could try changing it so it
> uses the code starting at 101 instead.
>
>
> also your claim about JS should be investigated because I do not think it
> should be the case.
> but you may want to move this to a jira http://jira.freeswitch.org
>
> As for the asterisk comparison,
> not sure how to answer you, that's your decision.
>
>
>
> On Mon, Dec 7, 2009 at 9:28 AM, eaf <erandr-junk at usa.net> wrote:
>
>>
>> Here is what I found...
>>
>> I tried high-priority scheduling as per your suggestion, reniced the
>> program
>> explicitly, rewrote timer thread to sleep on cond. variable and activate
>> only when there are timers and only when the timer actually had to be
>> clicked, turned off SQL thread and removed polling from sofia profile
>> thread.
>>
>> That pretty much eliminated all idle 1ms sleepers that were there except
>> for
>> three in sofia itself (su_epoll_port). And when I was about to be happy, I
>> found that two outgoing calls through my VOIP providers when bridged
>> together showed terrible distortions. I undid all my changes, tried 1.0.4,
>> trunk (noticed btw that when I bridge two calls via loopback in JS in the
>> trunk I must keep JS running, or the calls get terminated - NOT the same
>> as
>> in 1.0.4 where exitting JS left calls running), got pretty much the same
>> sad
>> results. At the same time calls bridged by freeswitch between LAN and any
>> of
>> the VOIP providers behaved just fine. And calls bridged by Asterisk any
>> way
>> were fine too. So that pretty much looked like the end of the freeswitch
>> trials for me.
>>
>> But then I timed your code, mine and found that all those 1ms sleeps that
>> your timer thread was doing (and all those pollers were doing as well)
>> were
>> actually 4ms sleeps because you know what unless kernel is configured with
>> HZ=1000, you can't sleep for less than 4ms (HZ=250) or perhaps even 10ms
>> (HZ=100). Mine was 250.
>>
>> This actually meant that the original timer thread was firing once,
>> sleeping
>> for 4ms, firing 3 more times back-to-back, sleeping for 4ms more, firing 4
>> times back-to-back, etc. It was still firing 20ms timers on time, but 30ms
>> ones of course were not, since 30ms doesn't divide by 4 evenly. Plus
>> whoever
>> relied on runtime.reference or switch_micro_time_now() were kind of
>> screwed
>> because both were running jumpy. Plus whoever assumed that apr_sleep(1000)
>> or cond_yield() was sleeping for 1ms were also in for a surprise. It felt
>> satisfying to find that, however it didn't explain why the same
>> distortions
>> were observed with rewritten timer thread and disabled RTP timers.
>>
>> Anyway, I sighed (pretty much like you) and recompiled the kernel with
>> HZ=1000. Recompiling kernel on these ALIX boards is fun. If smth goes
>> south,
>> you need to hook up serial console and see what the heck went wrong.
>>
>> That eliminated distortions, ha! But made freeswitch more CPU hungry. Now
>> the remaining 1ms threads sitting in sofia epoll were really polling for
>> 1ms, not 4, and freeswitch was consistently sitting in the first line of
>> the
>> top chart showing 3% CPU utilization when idle.
>>
>> Don't know whether it's because of the remaining epolls in sofia or
>> whether
>> it's because there are still some threads left in freeswitch that I
>> neglected to change because they were sleeping with 100ms interval, so I
>> figured, who cares. Maybe when all things come together (sofia, 100ms*N)
>> freeswitch ends up spending 3% of CPU while doing pretty much nothing.
>>
>> Btw, compared with Asterisk, the latter is not even visible on the first
>> top's screen and spends 1% CPU when bridging two G711 calls and recording
>> them to disk.
>>
>> So, at this time I have both original Asterisk and FS setups running. One
>> is
>> seemless but clumsy in configuration, the other one is neat and stylish
>> but
>> too preoccupied with smth... Should I look into sofia epollers? That's
>> kind
>> of deep in the code. Or should I just stick with Asterisk?
>>
>
>
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-- 
Anthony Minessale II

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