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From Ingo Rockel <iroc...@pironet-ndh.com>
Subject Re: Tomcat JVM using 99.9% cpu
Date Fri, 23 Sep 2005 08:06:56 GMT
Very interesting links, thanx a lot :)

Jost Richstein schrieb:
> For more information see:
> 
> http://fishbowl.pastiche.org/2005/04/27/the_string_memory_gotcha
> http://bugs.sun.com/bugdatabase/view_bug.do?bug_id=6294060
> http://bugs.sun.com/bugdatabase/view_bug.do?bug_id=4513622
> 
> Ingo Rockel wrote:
> 
>> Hi Jost,
>>
>> do you have any bug numbers concerning the OOM-issue with 
>> String.trim() and substring at hand?
>>
>> cheers,
>>
>> Ingo
>>
>> Jost Richstein schrieb:
>>
>>> Most likely the garbage collector causes your CPU load.
>>> At some point there is not enough memory and the collector tries
>>> to free some of it and tries and tries and tries. Usually your
>>> server runs fine even with this CPU load, it even sends quick
>>> responses (the collector has a low priority), but it results
>>> sooner or later in an "out of memory" exception.
>>>
>>> We had the same problem and the solution was not so obvious
>>> (for me at least). The memory leak we experienced was a
>>> String.substring() and String.trim() problem. These methodes
>>> do not create new Strings instead they point into the underlying
>>> char-array of the original String. The consequence is that the
>>> original string can not be freed until all substrings and trims
>>> are freed. If you are using caches, static strings - check this.
>>> And, by the way: all is fine if you are using
>>> new String(str.substring()). It is well documented in the bug
>>> parade.
>>>
>>>
>>>
>>> Azariah Jeyakumar wrote:
>>>
>>>> Hi,
>>>>
>>>> Has anyone seen Tomcat JVM using 99.9% cpu when there is no HTTP 
>>>> load at all? The JSP pages are accessible fine without any loss in 
>>>> functionality, but the machine is sluggish (expectedly, as the JVM 
>>>> is using all the CPU). If tomcat is restarted, the problem goes away 
>>>> and the CPU usage returns to normal.
>>>>
>>>> I have not been able to reproduce the problem at will. It has been 
>>>> noticed only twice or so in the past week, out of hundreds of attempts.
>>>> I have seen other posts asking to tweak the settings like socket_* 
>>>> in workers.properties files. But since I have not been able to 
>>>> reproduce the problem at will, I am hesitant to change the 
>>>> parameters, not knowing which change will fix the problem.
>>>>
>>>> Thanks for any input or pointers on:
>>>> - the nature of the problem that causes this 99.9% CPU usage
>>>> - how to reproduce the problem
>>>> - what parameters should be set in workers.properties file or 
>>>> elsewhere to avoid this problem in the future.
>>>>
>>>> I am using Tomcat 5.0.28, Apache 2.x, jk2, Sun JRE 1.4.2_08  on Suse 
>>>> Linux Enterprise Server (SLES 9 SP2).
>>>>
>>>> Thanks
>>>> Azariah
>>>>
>>>>
>>>
>>>
>>>
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>>
>>
> 
> 
> 
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