2-nd round RFR (M) 8046246: the constantPoolCacheOopDesc::adjust_method_entries() used in RedefineClasses does not scale

[serguei.spitsyn at oracle.com]

The hotspot webrev below addresses the Coleen's comments from the 1-st 
review round.

Open hotspot webrev:
http://cr.openjdk.java.net/~sspitsyn/webrevs/2015/hotspot/8046246-JVMTI-redefscale.2/

Open jdk (new unit test) webrev:
http://cr.openjdk.java.net/~sspitsyn/webrevs/2015/jdk/8046246-JVMTI-manymethods.1/

Thanks,
Serguei


On 2/18/15 9:45 PM, serguei.spitsyn at oracle.com wrote:
> Please, review the fix for:
>   https://bugs.openjdk.java.net/browse/JDK-8046246
>
>
> Open hotspot webrevs:
> http://cr.openjdk.java.net/~sspitsyn/webrevs/2015/hotspot/8046246-JVMTI-redefscale.1/ 
>
>
> Open jdk (new unit test) webrev:
> http://cr.openjdk.java.net/~sspitsyn/webrevs/2015/jdk/8046246-JVMTI-manymethods.1/ 
>
>
>
> Summary:
>
>    This performance/scalability issue in class redefinition was 
> reported by HP and the Enterprise Manager team.
>    The following variants of the adjust_method_entries() functions do 
> not scale:
>      ConstantPoolCache::adjust_method_entries()
>      klassVtable::adjust_method_entries()
>      klassItable::adjust_method_entries()
>      InstanceKlass::adjust_default_methods()
>
>    The ConstantPoolCache::adjust_method_entries() is the most important.
>
>    The approach is to use the holder->method_with_idnum() like this:
>      Method* new_method = 
> holder->method_with_idnum(old_method->orig_method_idnum());
>      if (old_method != new_method) {
>          <replace old_method with new_method>
>      }
>
>      New algorithm has effectiveness O(M) instead of original O(M^2),
>      where M is count of methods in the class.
>      The new test (see webrev above) was used to mesure CPU time 
> consumed by the
>      ConstantPoolCache::adjust_method_entries() in both original and 
> new approach.
>
>      The performance numbers are:
>
> --------------------------------------------------------------------------------------- 
>
>      Methods: ------ 1,000 --------------- 10,000 ----------------- 
> 20,000
> --------------------------------------------------------------------------------------- 
>
>      Orig:         600,000 nsec (1x)   60,500,000 nsec (~100x) 
> 243,000,000 nsec (~400x)
>      New:           16,000 nsec (1x)      178,000 nsec (~10x) 355,000 
> nsec  (~20x)
> --------------------------------------------------------------------------------------- 
>
>
>
>
> Testing:
>   In progress: VM SQE RedefineClasses tests, JTREG 
> java/lang/instrument, com/sun/jdi tests
>
>
> Thanks,
> Serguei
>