Java theory and practice: Urban performance legends
Posted: Tue Jul 18, 2006 2:36 am
http://www-128.ibm.com/developerworks/j ... banLegends
The Java™ language is the target of a lot of abuse for performance. And while some of it may well be deserved, a tour of message board and newsgroup postings on the subject shows that there is a great deal of misunderstanding about how a Java Virtual Machine (JVM) actually works. In this month's Java theory and practice, Brian Goetz pokes some holes in the oft-repeated performance myth of slow allocation in JVMs.
Pop quiz: Which language boasts faster raw allocation performance, the Java language, or C/C++? The answer may surprise you -- allocation in modern JVMs is far faster than the best performing malloc implementations. The common code path for new Object() in HotSpot 1.4.2 and later is approximately 10 machine instructions (data provided by Sun; see Resources), whereas the best performing malloc implementations in C require on average between 60 and 100 instructions per call (Detlefs, et. al.; see Resources). And allocation performance is not a trivial component of overall performance -- benchmarks show that many real-world C and C++ programs, such as Perl and Ghostscript, spend 20 to 30 percent of their total execution time in malloc and free -- far more than the allocation and garbage collection overhead of a healthy Java application (Zorn; see Resources).
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The Java™ language is the target of a lot of abuse for performance. And while some of it may well be deserved, a tour of message board and newsgroup postings on the subject shows that there is a great deal of misunderstanding about how a Java Virtual Machine (JVM) actually works. In this month's Java theory and practice, Brian Goetz pokes some holes in the oft-repeated performance myth of slow allocation in JVMs.
Pop quiz: Which language boasts faster raw allocation performance, the Java language, or C/C++? The answer may surprise you -- allocation in modern JVMs is far faster than the best performing malloc implementations. The common code path for new Object() in HotSpot 1.4.2 and later is approximately 10 machine instructions (data provided by Sun; see Resources), whereas the best performing malloc implementations in C require on average between 60 and 100 instructions per call (Detlefs, et. al.; see Resources). And allocation performance is not a trivial component of overall performance -- benchmarks show that many real-world C and C++ programs, such as Perl and Ghostscript, spend 20 to 30 percent of their total execution time in malloc and free -- far more than the allocation and garbage collection overhead of a healthy Java application (Zorn; see Resources).
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