jmap -permstat reports only 50-60% of permgen memory usage.

###@###.### wrote:
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Hi,

I'd like to contribute this patch. I need a reviewer who is familiar
with the Hotspot Serviceability Agent.

The description of the patch is something like:

        Accounting for more memory uses associated with class metadata
        in PermGen which "jmap -permstat" misses.

In a small test, the "jmap -permstat" command reports only about
50-60% of the permgen memory usage (compared to the actual usage of
permgen based on what the "jmap" command reports). This patch will
increase the number up to 80-90%.

Here's the patch which is based on a very recent version of
http://hg.openjdk.java.net/jdk7/jdk7

--- a/agent/src/share/classes/sun/jvm/hotspot/tools/PermStat.java
+++ b/agent/src/share/classes/sun/jvm/hotspot/tools/PermStat.java
@@ -266,45 +266,51 @@
       out.println();
    }

+ private static long objectSize(Oop oop) {
+ return oop == null ? 0L : oop.getObjectSize();
+ }
+
+ // Don't count the shared empty arrays
+ private static long arraySize(Array arr) {
+ return arr.getLength() != 0L ? arr.getObjectSize() : 0L;
+ }
+
    private long computeSize(InstanceKlass k) {
       long size = 0L;
- // InstanceKlass object size
+ // the InstanceKlass object itself
       size += k.getObjectSize();

- // add ConstantPool size
- size += k.getConstants().getObjectSize();
+ // Constant pool
+ ConstantPool cp = k.getConstants();
+ size += cp.getObjectSize();
+ size += objectSize(cp.getCache());
+ size += objectSize(cp.getTags());

- // add ConstantPoolCache, if any
- ConstantPoolCache cpCache = k.getConstants().getCache();
- if (cpCache != null) {
- size += cpCache.getObjectSize();
+ // Interfaces
+ size += arraySize(k.getLocalInterfaces());
+ size += arraySize(k.getTransitiveInterfaces());
+
+ // Inner classes
+ size += objectSize(k.getInnerClasses());
+
+ // Fields
+ size += objectSize(k.getFields());
+
+ // Methods
+ ObjArray methods = k.getMethods();
+ int nmethods = (int) methods.getLength();
+ if (nmethods != 0L) {
+ size += methods.getObjectSize();
+ for (int i = 0; i < nmethods; ++i) {
+ Method m = (Method) methods.getObjAt(i);
+ size += m.getObjectSize();
+ size += objectSize(m.getConstMethod());
+ }
       }

- // add interfaces size
- ObjArray interfaces = k.getLocalInterfaces();
- size += (interfaces.getLength() != 0L)? interfaces.getObjectSize() : 0L;
- ObjArray transitiveInterfaces = k.getTransitiveInterfaces();
- size += (transitiveInterfaces.getLength() != 0L)?
transitiveInterfaces.getObjectSize() : 0L;
-
- // add inner classes size
- TypeArray innerClasses = k.getInnerClasses();
- size += innerClasses.getObjectSize();
-
- // add fields size
- size += k.getFields().getObjectSize();
-
- // add methods size
- ObjArray methods = k.getMethods();
- size += (methods.getLength() != 0L)? methods.getObjectSize() : 0L;
- TypeArray methodOrdering = k.getMethodOrdering();
- size += (methodOrdering.getLength() != 0L)?
methodOrdering.getObjectSize() : 0;
-
- // add each method's size
- int numMethods = (int) methods.getLength();
- for (int i = 0; i < numMethods; i++) {
- Method m = (Method) methods.getObjAt(i);
- size += m.getObjectSize();
- }
+ // MethodOrdering - an int array that records the original
+ // ordering of methods in the class file
+ size += arraySize(k.getMethodOrdering());

       return size;
    }
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