Megaco Avalanche! (was: ets:update_counter/3 taking a looooong time!)

Micael Karlberg micael.karlberg@REDACTED
Tue May 6 14:09:34 CEST 2003

Hi Peter,

Another suggestion came up. Try eprof and compare the 
result to fprof (in case fprof has a bug).


Peter-Henry Mander writes:
 > Hi Micael,
 > Thanks for the three suggestions. Since I managed to hack the problem 
 > into submission and obtain a sufficiently fast result, I'm probably not 
 > going to be able to try them until after more urgent hacking is 
 > finished. But when I do I'll try to isolate and diagnose what was going on.
 > A curious symptom was that the two nodes either end of the megaco 
 > signalling link where running idle, as if they where waiting for each 
 > other. Could it be that they were franticly garbage collecting or 
 > something? The CPU usage was practically zero.
 > Q1: no, I haven't changed any default values. I noticed the 
 > reset_trans_id_counter function but ignored it because it was never 
 > being called.
 > Q2: The results were the same whether "hot" or "cold." I assume you are 
 > hinting at the garbage collector kicking in?
 > S2: I have a different test that "churns" the calls very quickly, 
 > setting them up and tearing them down without holding them and without 
 > any pause between. This one sustains almost 400 calls setup and teardown 
 > every second, so it is clear to me that ets:update_counter/3 *must* be 
 > capable of at least this rate. When I attempted this new test where 
 > calls were setup without tearing them down I was expecting at least 
 > 400/second if not more. So I am very puzzled as to why I have to 
 > introduce "breathing time" when before it wasn't necessary. The only 
 > difference is that memory is being rapidly consumed by the call 
 > processes to store the call contexts.
 > If I manage to reproduce the symptoms with a subset of the code, would 
 > you be interested in reading it? I must warn you that it is *very* 
 > "experimental!" i.e. hacked code.
 > Pete.
 > Micael Karlberg wrote:
 > Hi Peter,
 > I have been trying to reproduce your problem without success.
 > I have some questions and suggestions.
 >    q1: Have you changed the max counter value (max_trans_id)?
 >        A small value would lead to reset_trans_id_counter more
 >        often (I admit that from the fprof output that does not
 >        seem to be the case).
 >    q2: The fprof results included here, where they produced
 >        after the system beeing "warmed up"?
 >    s1: When fprof'ing, use fprof:apply(Func, Args, OptionList)
 >        and include the megaco system processes megaco_config
 >        and megaco_monitor ({procs, [self(),megaco_config,megaco_monitor]}).
 >    s2: In order to get more reliable results, run more then one
 >        set of call-setup: N*(add, modify & subtract).
 >    s3: Try setting prio of the megaco_config process to high.
 > /BMK

Micael Karlberg          Ericsson AB, Älvsjö Sweden
Tel:  +46 8 727 5668     EAB/UHK/KD - OTP Product Development
ECN:  851 5668           Mail: micael.karlberg@REDACTED
Fax:  +46 8 727 5775    

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