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From "Aleksey Shipilev" <aleksey.shipi...@gmail.com>
Subject [classlib][pack200][performance] Profiling unpacking scenario
Date Tue, 08 Jul 2008 17:43:39 GMT

I took the liberty of profiling of pack200 implementation on unpacking
scenario. Source data was obtained from Eclipse JDT jars, repacked in
single 60 Mb jar file, then packed with pack200 from Sun's JDK (-E9
used), resulting in 20 Mb pack200-compressed file. Then Sun JDK
1.6.0_05 (Windows, -server) was used together with hprof (cpu=time) to
obtain the profile. My patch from HARMONY-5900 is onboard. The head of
the profile looks like this:

4.76% org.apache.harmony.unpack200.bytecode.ClassConstantPool.addNested
4.22% java.util.HashMap.getEntry
2.99% java.util.AbstractList$Itr.next
2.92% java.util.AbstractList$Itr.hasNext
2.84% java.util.ArrayList.get
2.43% java.util.AbstractList$Itr.next
2.41% java.util.HashMap.containsKey
2.15% org.apache.harmony.unpack200.IcBands.getRelevantIcTuples
2.00% java.util.HashSet.contains
1.57% java.io.DataOutputStream.writeUTF

Composite occupancy:

18.4% java.util.AbstractList
18.0% java.util.HashMap
15.8% java.util.ArrayList
10.5% o.a.h.unpack200.bytecode.ClassConstantPool.*
5.3%  o.a.h.unpack200.bytecode.CPUTF8.* (hashcode mostly)
4.5% java.io.*
4.5% java.lang.String.*
4.4% o.a.h.unpack200.bytecode.ByteCode.*
3.9%  o.a.h.unpack200.bytecode.Ic{Tuple|Bands}.*
14.7% other

So the main concern is Collections usage. ClassConstantPool uses Lists
excessively, so I suspect the significant amount of time is spent

Timings for the scenario (the less the better):
Harmony's pack200: 67 secs
Sun's pack200: 6 secs

Yep, 10 times faster.


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