Startup Improvement with -Xverify:none

[Mandy Chung]

Mark,

I did some experiments in running the startup benchmarks with 
-Xverify:none to get a closer approximation of the potential gain if the 
module system supports pre-verification.

http://cr.openjdk.java.net/~mchung/startup_measurement/startup.result.b63.noverify

Summary (based on the measurement with the refworkload benchmarks)
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1) Pre-verification could improve startup time by 8-13%.
2) Class data sharing improves the startup time by 4.5-18.5%, half of 
the time is class parsing time. Class parsing could be one candidate to 
look for optimization opportunity. Need further brainstorming.
3) Looking up application classes takes about 2.27-7.0%.  With module 
system, class lookup should speed up since the module system knows which 
module a class belongs to.  Need to measure this when it's ready.
4) The data archive (JRE/bin/client/classes.jsa) is generated at JRE 
install time with a predefined classlist.  With modularized JDK, we need 
to make sure either the class data sharing technique to work with JDK 
modules (e.g. regenerate the classes.jsa when new JDK module is 
installed), or other optimization in place that the startup time 
improvement due to class data sharing would still be observed.

FYI.  The changeset for my HotSpot instrumentation is already in 
hotspot-rt [1].

Mandy

[1] http://hg.openjdk.java.net/jdk7/hotspot-rt/hotspot/rev/6a93908f268f