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From Ingo Rockel <>
Subject Re: Tomcat JVM using 99.9% cpu
Date Fri, 23 Sep 2005 07:42:41 GMT
Hi Jost,

do you have any bug numbers concerning the OOM-issue with String.trim() 
and substring at hand?



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 
>> 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 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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