CR 8005604: HPROF should report the actual instance size
Aleksey Shipilev
aleksey.shipilev at oracle.com
Sat Dec 29 01:14:06 PST 2012
Hi guys,
This issue popped out (again?) in the course of @Contended work, which
does the padding around fields in some corner cases. HPROF just iterates
the fields to deduce the instance size, which can give a terribly wrong
instance size estimate.
I have filed CR 8005604 to track this.
FWIW, the fix appears to be very simple, we can reuse the instance size
data already available in instanceKlass, like this:
--- a/src/share/vm/services/heapDumper.cpp Mon Dec 24 11:46:38 2012 -0800
+++ b/src/share/vm/services/heapDumper.cpp Sat Dec 29 13:08:51 2012 +0400
@@ -772,33 +772,7 @@
u4 DumperSupport::instance_size(Klass* k) {
HandleMark hm;
instanceKlassHandle ikh = instanceKlassHandle(Thread::current(), k);
-
- int size = 0;
-
- for (FieldStream fld(ikh, false, false); !fld.eos(); fld.next()) {
- if (!fld.access_flags().is_static()) {
- Symbol* sig = fld.signature();
- switch (sig->byte_at(0)) {
- case JVM_SIGNATURE_CLASS :
- case JVM_SIGNATURE_ARRAY : size += oopSize; break;
-
- case JVM_SIGNATURE_BYTE :
- case JVM_SIGNATURE_BOOLEAN : size += 1; break;
-
- case JVM_SIGNATURE_CHAR :
- case JVM_SIGNATURE_SHORT : size += 2; break;
-
- case JVM_SIGNATURE_INT :
- case JVM_SIGNATURE_FLOAT : size += 4; break;
-
- case JVM_SIGNATURE_LONG :
- case JVM_SIGNATURE_DOUBLE : size += 8; break;
-
- default : ShouldNotReachHere();
- }
- }
- }
- return (u4)size;
+ return (u4)ikh->size_helper();
}
// dumps static fields of the given class
Please let me know if you have troubles with pushing this. If not, I can
get the proper due diligence to get this fixed.
Thanks,
Aleksey.
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