On 01/25/2013 05:34 PM, Aleksey Shipilev wrote:
On 01/25/2013 08:02 PM, Peter Levart wrote:
On 01/25/2013 06:35 AM, David Holmes wrote:
On 25/01/2013 2:36 AM, Peter Levart wrote:
On 01/24/2013 04:45 PM, Peter Levart wrote:
...so it seems that in both cases, adding a boolean to j.l.Class wastes
8 bytes per Class object :-(
Seems to be the case, we are hitting the 8-byte alignment boundary.
java-object-layout [1] on jdk7u12:
$ java -jar ~/projects/java-object-layout/target/java-object-layout.jar
java.lang.Class
Running 64-bit HotSpot VM.
Using compressed references with 3-bit shift.
Objects are 8 bytes aligned.
java.lang.Class
offset size type description
0 12 (assumed to be the object header)
12 4 Constructor Class.cachedConstructor
16 4 Class Class.newInstanceCallerCache
20 4 String Class.name
24 4 SoftReference Class.declaredFields
28 4 SoftReference Class.publicFields
32 4 SoftReference Class.declaredMethods
36 4 SoftReference Class.publicMethods
40 4 SoftReference Class.declaredConstructors
44 4 SoftReference Class.publicConstructors
48 4 SoftReference Class.declaredPublicFields
52 4 SoftReference Class.declaredPublicMethods
56 4 ClassRepository Class.genericInfo
60 4 Object[] Class.enumConstants
64 4 Map Class.enumConstantDirectory
68 4 Map Class.annotations
72 4 Map Class.declaredAnnotations
76 4 AnnotationType Class.annotationType
80 4 ClassValueMap Class.classValueMap
84 12 (alignment/padding gap)
What's this? why 12 bytes?
96 4 int Class.classRedefinedCount
100 4 int Class.lastRedefinedCount
104 (object boundary, size estimate)
But, otherwise, can't we use java.lang.ClassValue to associate this flag
with each class?
-Aleksey.
[1] https://github.com/shipilev/java-field-layout
