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Performance. The JVM is an extremely fast platform given its feature set. It also has a coherent and powerful concurrency specification that is stable. While

Performance. The JVM is an extremely fast platform given its feature set. It also has a coherent and powerful concurrency specification that is stable. While it is possible to have very low latency systems in Java, it requires a bit more work, and people tend to gravitate to C++ if the 3x penalty from C is too high. But aside from the latency, if you can deal with full GCs, Java is a data throughput monster. The default GC is actually very good in most cases, and the JVM GCs allow significant performance tuning, which is a discipline in its own right. It will be interesting if the low latency Z Garbage Collector introduced in JDK11 eventually removes one of the last complaints on Java performance.

dwaite 8y ago
Java has issues both with latency and memory usage due to the garbage collector and general age of the language (missing modern features like value types). Performance is.. complex. The lack of value types causes a lot more indirection, the hotspot compiler patches away some of it, the copy collector will compress connected objects together so that they will fit 'automagically' into CPU cache. Unoptimized Java code may often run faster than unoptimized C/C++ code, but Java gives you only vague, global flags for attempting to tune memory behavior and code generation. For monolithic Java applications, you can have a lot of different memory patterns internally (short term objects for the web stack, medium-term objects for transactional state, plus long-term objects representing accumulated state) which can really muck with the garbage collector's assumptions around generations. For server applications, this can cause things like heavy load causing request/response short-term state to be promoted to the mature generation. You start having to break up monolithic applications for performance reasons. But, that still is being a victim of your success - and you would be better off by default creating the first version of your application in a language that allows your developers to iterate quickly.

dwaite 8y ago

Java has issues both with latency and memory usage due to the garbage collector and general age of the language (missing modern features like value types). Performance is.. complex. The lack of value types causes a lot more indirection, the hotspot compiler patches away some of it, the copy collector will compress connected objects together so that they will fit 'automagically' into CPU cache. Unoptimized Java code may often run faster than unoptimized C/C++ code, but Java gives you only vague, global flags for attempting to tune memory behavior and code generation. For monolithic Java applications, you can have a lot of different memory patterns internally (short term objects for the web stack, medium-term objects for transactional state, plus long-term objects representing accumulated state) which can really muck with the garbage collector's assumptions around generations. For server applications, this can cause things like heavy load causing request/response short-term state to be promoted to the mature generation. You start having to break up monolithic applications for performance reasons. But, that still is being a victim of your success - and you would be better off by default creating the first version of your application in a language that allows your developers to iterate quickly.