Differences

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--- java [2012/12/04 23:57]
a
+++ java [2012/12/05 00:07]
a [Good/best practices]
@@ Line 28: / Line 28: @@
 | **-XX:MinHeapFreeRatio** | default is 40%. JVM will allocate memory to always have as minimum 40% of free memory. When -Xmx = -Xms, it's useless. |
 | **-XX:MaxHeapFreeRatio:** | default is 70%. The same as Min, to avoid unecessary memory allocation. |
+<note important>
+**A nice gotcha...** \\
+Major collection don't run until tenured is full.
+This mean that using -Xmx1024, current heap could be 750MB with 500MB of "dead" object. If the JVM is idle, it could stay like that during a very long time => wasting 500MB or RAM for an idle JVM !
+</note>
 <note tip>
@@ Line 36: / Line 43: @@
 ==== Good/best practices ====
+FIXME
 ==== Examples ====
+tying to limit jvm to ~2G of RAM (java x86_64)
+    java -Xms512m -Xmx2G -XX:+UseCompressedOops -server -XX:MaxPermSize128
+java (i386)
+    java -Xms1400m -Xmx2G -XX:MaxPermSize=128m -server
 ==== Troubleshooting ====