In ClassFileParser::parse_methods, the four arrays -- methods_annotations, methods_parameter_annotations, methods_default_annotations and methods_type_annotations are allocated, even if they would contain all NULL values.

It may be possible to apply a patch like this to avoid the unnecessary allocations. I tested with running Eclipse on JDK8/x64 VM and the saving is about 4MB, or about 7% of total class meta data loaded by Eclipse.


hg diff src/share/vm/classfile/classFileParser.cpp
diff -r 36171820ba15 src/share/vm/classfile/classFileParser.cpp
--- a/src/share/vm/classfile/classFileParser.cpp Mon Jan 07 13:10:37 2013 -0800
+++ b/src/share/vm/classfile/classFileParser.cpp Thu Jan 10 06:21:54 2013 -0800
@@ -2452,27 +2452,35 @@
         *has_default_methods = true;
       }
       methods->at_put(index, method());
+ if (method_annotations != NULL) {
       if (*methods_annotations == NULL) {
         *methods_annotations =
              MetadataFactory::new_array<AnnotationArray*>(loader_data, length, NULL, CHECK_NULL);
       }
       (*methods_annotations)->at_put(index, method_annotations);
+ }
+ if (method_parameter_annotations != NULL) {
       if (*methods_parameter_annotations == NULL) {
         *methods_parameter_annotations =
             MetadataFactory::new_array<AnnotationArray*>(loader_data, length, NULL, CHECK_NULL);
       }
       (*methods_parameter_annotations)->at_put(index, method_parameter_annotations);
+ }
+ if (method_default_annotations != NULL) {
       if (*methods_default_annotations == NULL) {
         *methods_default_annotations =
             MetadataFactory::new_array<AnnotationArray*>(loader_data, length, NULL, CHECK_NULL);
       }
       (*methods_default_annotations)->at_put(index, method_default_annotations);
+ }
+ if (method_type_annotations != NULL) {
       if (*methods_type_annotations == NULL) {
         *methods_type_annotations =
              MetadataFactory::new_array<AnnotationArray*>(loader_data, length, NULL, CHECK_NULL);
       }
       (*methods_type_annotations)->at_put(index, method_type_annotations);
     }
+ }
 
     if (_need_verify && length > 1) {
       // Check duplicated methods


This bug seems to have been introduced in JDK8. In JDK7, checks similar to the patch above are performed (this is the latest jdk7u code as of the filing of this bug).

http://hg.openjdk.java.net/jdk7u/jdk7u/hotspot/file/0d5d62e38450/src/share/vm/classfile/classFileParser.cpp

Thu Oct 11 14:46:20 2012 -0700
changeset 4034 cc602d511176

     2393 if (method_annotations.not_null()) {
     2394 if (methods_annotations.is_null()) {
     2395 objArrayOop md = oopFactory::new_system_objArray(length, CHECK_(nullHandle));
     2396 methods_annotations = objArrayHandle(THREAD, md);
     2397 }
     2398 methods_annotations->obj_at_put(index, method_annotations());
     2399 }
     2400 if (method_parameter_annotations.not_null()) {
     2401 if (methods_parameter_annotations.is_null()) {
     2402 objArrayOop md = oopFactory::new_system_objArray(length, CHECK_(nullHandle));
     2403 methods_parameter_annotations = objArrayHandle(THREAD, md);
     2404 }
     2405 methods_parameter_annotations->obj_at_put(index, method_parameter_annotations());
     2406 }
     2407 if (method_default_annotations.not_null()) {
     2408 if (methods_default_annotations.is_null()) {
     2409 objArrayOop md = oopFactory::new_system_objArray(length, CHECK_(nullHandle));
     2410 methods_default_annotations = objArrayHandle(THREAD, md);
     2411 }
     2412 methods_default_annotations->obj_at_put(index, method_default_annotations());
     2413 }