[erlang-questions] High CPU usage problem

Guilherme Andrade <>
Sat Dec 20 17:49:41 CET 2014


Now that I look more carefully, it looks like your system is spending a
whole lot of CPU time (~75%) in kernel space. Some system call (or
calls) is taking away way too many resources.


On 20-12-2014 16:19, Guilherme Andrade wrote:
> Hello gongtao,
>
> Besides 'message_queue_len', I would also look into 'reductions' over
> time (also using process_info/2.)
>
> As for big message queues, if the CPU is not overloaded, in most cases
> it's due to single processes becoming a bottleneck, whether due to IO
> and/or heavy crunching; if they can be pooled or split into multiple
> ones, the better. However, you say that CPU is topping at 100%, so
> it's most likely that it's just too heavy.
>
> Long-running NIFs could also cause weird behaviour in the scheduler.
>
> This dirty (multiple) one-liner should give you some insight into
> reduction count:
>
> ------------------
> rp([{-Reduc, Pid, case process_info(Pid, registered_name) of
> {registered_name,Name} -> Name; _ -> '_' end} ||
>     {Reduc, Pid} <-
>     lists:foldl(
>         fun(Pid, L) when length(L) > 40 ->
>                 SL = lists:sublist(lists:keysort(1, L), 20),
>                 case process_info(Pid, reductions) of
>                     {reductions,Reduc} -> [{-Reduc, Pid} | SL];
>                     undefined -> L
>                 end;
>             (Pid, L) ->
>                 case process_info(Pid, reductions) of
>                     {reductions,Reduc} -> [{-Reduc, Pid} | L];
>                     undefined -> L
>                 end
>         end, [], erlang:processes())]).
> ------------------
>
>
> Cheers,
>
> On 20-12-2014 12:03, gongtao wrote:
>> hello everyone:
>>     I am a programmer from china.I have a problem with my game
>> server.There is 8193 processes in my erlang node.But the cpu usage is
>> nearly full,and the computer have 24 cpus.I looked some erlang
>> processes info,find the message_queue_len of process is very big,more
>> than 1000 sometimes.The disk io and net io are normal,memory is
>> normal.My erlang version is R15B03.I don't know why.
>>     My english is poor.There are same informations from system.Hope
>> you can understand.
>>     Looking forward to your reply.
>>     Thanks.
>>
>> -bash-4.2$ sar -u 2 10
>> Linux 2.6.32-279.el6.x86_64          12/20/2014      _x86_64_      
>>  (24 CPU)
>>
>> 06:33:37 PM     CPU     %user     %nice   %system   %iowait    %steal
>>     %idle
>> 06:33:39 PM     all     11.21      0.00     75.04      0.00      0.00
>>     13.75
>> 06:33:41 PM     all     10.91      0.00     77.22      0.00      0.00
>>     11.86
>> 06:33:43 PM     all     12.08      0.00     75.96      0.00      0.00
>>     11.97
>> 06:33:45 PM     all     10.50      0.00     77.71      0.00      0.00
>>     11.79
>> 06:33:47 PM     all     11.09      0.00     76.75      0.00      0.00
>>     12.16
>> 06:33:49 PM     all     11.07      0.00     76.03      0.00      0.00
>>     12.90
>> 06:33:51 PM     all     12.07      0.00     75.27      0.00      0.00
>>     12.66
>> 06:33:53 PM     all     11.36      0.00     76.84      0.00      0.00
>>     11.80
>>
>>
>> | CPU Utilisation
>> -------------------------------------------------------------------------------------------------------------------------------------
>>     |
>> |---------------------------+-------------------------------------------------+
>>                                                                      
>>       |
>> |CPU  User%  Sys% Wait% Idle|0          |25         |50          |75
>>       100|                                                          
>>                   |
>> |  1  14.1  75.9   0.0  
>> 9.9|UUUUUUUsssssssssssssssssssssssssssssssssssss    >|              
>>                                                               |
>> |  2   9.8  81.3   0.0  
>> 8.8|UUUUssssssssssssssssssssssssssssssssssssssss    >|              
>>                                                               |
>> |  3  11.6  76.9   0.0
>>  11.6|UUUUUssssssssssssssssssssssssssssssssssssss      >            
>>                                                                 |
>> |  4   7.6  82.3   0.0
>>  10.1|UUUsssssssssssssssssssssssssssssssssssssssss >   |            
>>                                                                 |
>> |  5  14.2  74.1   0.0
>>  11.7|UUUUUUUsssssssssssssssssssssssssssssssssssss  >  |            
>>                                                                 |
>> |  6   8.6  81.3   0.0
>>  10.1|UUUUssssssssssssssssssssssssssssssssssssssss  >  |            
>>                                                                 |
>> |  7  11.6  75.9   0.0
>>  12.6|UUUUUsssssssssssssssssssssssssssssssssssss       >            
>>                                                                 |
>> |  8   8.5  81.0   0.0
>>  10.5|UUUUssssssssssssssssssssssssssssssssssssssss >   |            
>>                                                                 |
>> |  9  11.7  76.1   0.0
>>  12.2|UUUUUssssssssssssssssssssssssssssssssssssss      >            
>>                                                                 |
>> | 10   9.1  80.8   0.0
>>  10.1|UUUUssssssssssssssssssssssssssssssssssssssss     >            
>>                                                                 |
>> | 11  10.2  76.5   0.0
>>  13.3|UUUUUssssssssssssssssssssssssssssssssssssss    > |            
>>                                                                 |
>> | 12   6.6  81.6   0.0
>>  11.7|UUUssssssssssssssssssssssssssssssssssssssss      >            
>>                                                                 |
>> | 13  12.1  75.3   0.0
>>  12.6|UUUUUUsssssssssssssssssssssssssssssssssssss      >            
>>                                                                 |
>> | 14   9.0  80.6   0.0
>>  10.4|UUUUssssssssssssssssssssssssssssssssssssssss     >            
>>                                                                 |
>> | 15  15.7  71.1   0.0
>>  13.2|UUUUUUUsssssssssssssssssssssssssssssssssss      >|            
>>                                                                 |
>> | 16   9.2  80.1   0.0
>>  10.7|UUUUssssssssssssssssssssssssssssssssssssssss  >  |            
>>                                                                 |
>> | 17  13.6  74.2   0.0
>>  12.1|UUUUUUsssssssssssssssssssssssssssssssssssss   >  |            
>>                                                                 |
>> | 18   7.2  82.1   0.0
>>  10.8|UUUsssssssssssssssssssssssssssssssssssssssss >   |            
>>                                                                 |
>> | 19  16.5  69.5   0.0
>>  14.0|UUUUUUUUssssssssssssssssssssssssssssssssss   >   |            
>>                                                                 |
>> | 20   7.3  81.2   0.0
>>  11.5|UUUssssssssssssssssssssssssssssssssssssssss    > |            
>>                                                                 |
>> | 21  17.8  69.0   0.0
>>  13.2|UUUUUUUUssssssssssssssssssssssssssssssssss     > |            
>>                                                                 |
>> | 22  11.4  77.2   0.0
>>  11.4|UUUUUssssssssssssssssssssssssssssssssssssss >    |            
>>                                                                 |
>> | 23  14.4  71.1   0.0
>>  14.4|UUUUUUUsssssssssssssssssssssssssssssssssss   >   |            
>>                                                                 |
>> | 24   5.8  81.7   0.0
>>  12.6|UUssssssssssssssssssssssssssssssssssssssss >     |            
>>                                                                 |
>> |---------------------------+-------------------------------------------------+
>>                                                                      
>>       |
>> |Avg  11.0  77.3   0.0
>>  11.7|UUUUUssssssssssssssssssssssssssssssssssssss >    |            
>>                                                                 |
>> |---------------------------+-------------------------------------------------+
>>  
>>
>>
>>
>>
>>
>> _______________________________________________
>> erlang-questions mailing list
>> 
>> http://erlang.org/mailman/listinfo/erlang-questions
>
> -- 
> Guilherme
>
> https://www.gandrade.net/
> PGP: 0x35CB8191 / 1968 5252 3901 B40F ED8A  D67A 9330 79B1 35CB 8191
>
>
> _______________________________________________
> erlang-questions mailing list
> 
> http://erlang.org/mailman/listinfo/erlang-questions

-- 
Guilherme

https://www.gandrade.net/
PGP: 0x35CB8191 / 1968 5252 3901 B40F ED8A  D67A 9330 79B1 35CB 8191

-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://erlang.org/pipermail/erlang-questions/attachments/20141220/02ec3dfc/attachment.html>
-------------- next part --------------
A non-text attachment was scrubbed...
Name: signature.asc
Type: application/pgp-signature
Size: 455 bytes
Desc: OpenPGP digital signature
URL: <http://erlang.org/pipermail/erlang-questions/attachments/20141220/02ec3dfc/attachment.bin>


More information about the erlang-questions mailing list