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From: Apache Wiki <wikidiffs@apache.org>
To: Apache Wiki <wikidiffs@apache.org>
Date: Wed, 05 Feb 2014 13:36:51 -0000
Message-ID: <20140205133651.30461.23323@eos.apache.org>
Subject: 
 =?utf-8?q?=5BTomcat_Wiki=5D_Trivial_Update_of_=22OutOfMemory=22_by_Konsta?=
 =?utf-8?q?ntinKolinko?=
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The "OutOfMemory" page has been changed by KonstantinKolinko:
https://wiki.apache.org/tomcat/OutOfMemory?action=3Ddiff&rev1=3D11&rev2=3D12

Comment:
Add TOC, remove dead link

  #format wiki
  #language en
+ =

+ <<TableOfContents>>
  =

  =3D How to Deal With Out Of Memory Errors =3D
  =

@@ -18, +20 @@

  An Out Of Memory can be thrown by several causes:
  =

   * A servlet trying to load a several GBytes file into memory will surely=
 kill the server. These kind of errors must be considered a simple bug in o=
ur program.
-  * To compensate for the data your servlet tries to load, you increase th=
e heap size so that there is no room to create the stack size for the threa=
ds that need to be created.  The memory required by each thread will vary b=
y OS but can be as high as 2M by default and in some OS's (like Debian Sarg=
e) is not reducible with the -Xss parameter. [[http://goobsoft.homeip.net/W=
iki.jsp?page=3DJavaDebianTuning|1]]  Rule of Thumb, use no more than 1G for=
 heap space in a 32-bit web application.
+  * To compensate for the data your servlet tries to load, you increase th=
e heap size so that there is no room to create the stack size for the threa=
ds that need to be created.  The memory required by each thread will vary b=
y OS but can be as high as 2M by default and in some OS's (like Debian Sarg=
e) is not reducible with the -Xss parameter. Rule of Thumb, use no more tha=
n 1G for heap space in a 32-bit web application.
   * Deep recursive algorithms can also lead to Out Of Memory problems. In =
this case, the only fixes are increasing the thread stack size ({{{-Xss}}})=
, or refactoring the algorithms to reduce the depth, or the local data size=
 per call.
   * A webapp that uses lots of libraries with many dependencies, or a serv=
er maintaining lots of webapps could exhauste the JVM PermGen space. This s=
pace is where the VM stores the classes and methods data. In those cases, t=
he fix is to increase this size. The Sun VM has the flag {{{-XX:MaxPermSize=
}}} that allows to set its size (the default value is 64M)
   * Hard references to classes can prevent the garbage collector from recl=
aiming the memory allocated for them when a ClassLoader is discarded. This =
will occur on JSP recompilations, and webapps reloads. If these operations =
are common in a webapp having these kinds of problems, it will be a matter =
of time, until the PermGen space gets full and an Out Of Memory is thrown.

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