Proxy.isProxyClass scalability (original) (raw)

Peter Levart peter.levart at gmail.com
Fri Jan 25 16:37:06 UTC 2013

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

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