Performance Analysis of Java Communications with and without CORBA

Transcription

1 Performance Analysis of Java Communications with and without CORBA Victor Giddings 3 Objective Interface Systems, Inc. Purpose Analyze performance of various Java-based distribution technologies Including CORBA-based Java Sockets-based Identify major contributors to performance Highlight difference in performance analysis between Java-based systems and system developed in other languages Additional contributions to performance Benchmarking difficulties 3 Objective Interface Systems, Inc

2 Typical C++ ORB Performance 1, 1, 1, 8 6 ORB Overhead Transport 5, 1, 15, 2, 25, 3, TCP Transport C++ ORB 3 Objective Interface Systems, Inc. 3 3 Typical C++ ORB Performance Transport cost TCP/Sockets costs Protocol stacks both sending and receiving side Propagation cost cost to send each byte over the communications media Usual result Zero-byte latency overhead of protocol packet header packetization Linear cost per payload byte possibly saw tooth from packetization ORB overhead Zero-byte contribution Connection resolution Message header Linear cost for marshalling 3 Objective Interface Systems, Inc

3 Java Transport Performance Java Sockets Class Transport C++ TCP Transport Java TCP Transport 3 Objective Interface Systems, Inc. 5 5 Java Transport Performance Java TCP communications adds another layer java.net.socket Class defined by J2SE Provided by Java run-time library Sun s implementation Native interface to O/S sockets Adds extra data copy Adds substantial overhead Zero-byte overhead greater than C++ ORB overhead! 3 Objective Interface Systems, Inc

4 Java ORB Performance Java ORB Overhead Java Sockets Class Transport C++ TCP Transport Java TCP Transport Java ORB 3 Objective Interface Systems, Inc. 7 7 Java ORB Performance Three components Transport O/S protocol stack + communications media Java sockets overhead ORB overhead Result is generally Zero-byte overhead plus Per-byte transfer time 3 Objective Interface Systems, Inc

5 Differing Java ORB Performance Java ORB A Java ORB B Java ORB C Java ORB D 3 Objective Interface Systems, Inc. 9 9 Differing Java ORB Performance Wide variation in performance of different Java ORBs Different zero-byte overhead and Different slope per byte cost Key ORB A ORBexpress for Java 2.4. alpha ORB B JacORB ORB C OpenORB 1.3. ORB D Sun JDK Objective Interface Systems, Inc

6 The Effect of Type Marshalling ORB A Pctets ORB A Longs ORB A Doubles ORB C Octets ORB C Longs ORB C Doubles 3 Objective Interface Systems, Inc The Effect of Type Marshalling Unlike other languages, cost of marshalling depends on type being marshaled Limited ability in Java to deal with machine representations of integers, floating points, strings, etc. Consistent across ORBs measured Sequence of octets faster than Sequence of longs faster than Sequence of doubles 3 Objective Interface Systems, Inc

7 Java Benchmarking Subtleties: Effects of Hot-Spot JVM Per Iteration Latency Iterations 3 Objective Interface Systems, Inc Java Benchmarking Subtleties: Effects of Hot-Spot JVM Sun Java HotSpot technology Introduced in JDK 1.3 Mandatory in JDK 1.4 JVM adaptively optimizes most used portions of code Running a portion of code more often makes it faster Benchmarks iterate same code to ensure statistical significance measure effects of unplanned interruptions Effect of iteration can be significant Example shows >2:1 improvement for large numbers of iterations Benchmark results Are always best case applications always slower For Java even farther from actual application performance 3 Objective Interface Systems, Inc

8 Java Benchmarking Subtleties: Effect of JVM Heap Allocation Zero-byte Two-Way Latency JVM Initial Heap (MB) Max Heap = 64M Max Heap = Initial Heap 3 Objective Interface Systems, Inc Java Benchmarking Subtleties: Effect of JVM Heap Allocation All Java programs create garbage Unused memory is reclaimed by JVM Garbage is created when program no longer holds a reference to previously allocated object (memory) But, garbage is collected unpredictably When memory is needed Periodically Can be affected (but not controlled) by JVM settings Garbage collection affects benchmarking Garbage accrues steadily; garbage is reclaimed sporadically Almost impossible to assign cost of garbage collection to computation that caused it Benchmarking can avoid garbage collection by large initial heap allocation 3 Objective Interface Systems, Inc