4 ms·

So, what exactly is escape analysis? Neither the article nor the comments here even touch on it.

idlewords 17y ago
http://en.wikipedia.org/wiki/Escape_analysis http://en.wikipedia.org/wiki/Escape_analysis In a nutshell, figuring out whether a variable or object is going to be entirely confined to a single thread and scope and using that information to perform optimizations (like sticking things into registers) or avoid unnecessary locking.
- sb 17y ago
  afair, the most important optimization there is that something can be allocated on the stack instead of the heap, which is quite an optimization. EDIT: it does not actually have anything to do what you can stick in registers--at least nothing comes to my mind w/o thinking too hard about it... relevant papers directly from the hotspot-jvm are: -kotzmann, moessenboeck, "escape analysis in the context of dynamic compilation and deoptimization" http://www.usenix.org/events/vee05/full_papers/p111-kotzmann.pdf http://www.usenix.org/events/vee05/full_papers/p111-kotzmann... -kotzmann, moessenboeck: "run-time support for optimizations based on escape analysis" http://ftp.ssw.uni-linz.ac.at/Research/Papers/Ko07/Ko07.pdf http://ftp.ssw.uni-linz.ac.at/Research/Papers/Ko07/Ko07.pdf
  - slava_pestov 17y ago
    Actually, once you've figured out that you can stack allocate an object, you can stick its instance variables in registers. This can be a huge win.
    - deleted 17y ago
      [deleted]
luke_s 17y ago
"The Java language does not offer any way to explicitly allocate an object on the stack, but this fact doesn't prevent JVMs from still using stack allocation where appropriate. JVMs can use a technique called escape analysis, by which they can tell that certain objects remain confined to a single thread for their entire lifetime, and that lifetime is bounded by the lifetime of a given stack frame. Such objects can be safely allocated on the stack instead of the heap. Even better, for small objects, the JVM can optimize away the allocation entirely and simply hoist the object's fields into registers." Taken from an IBM developerworks article here: http://www.ibm.com/developerworks/java/library/j-jtp09275.html http://www.ibm.com/developerworks/java/library/j-jtp09275.ht...

http://en.wikipedia.org/wiki/Escape_analysis http://en.wikipedia.org/wiki/Escape_analysis In a nutshell, figuring out whether a variable or object is going to be entirely confined to a single thread and scope and using that information to perform optimizations (like sticking things into registers) or avoid unnecessary locking.

sb 17y ago
afair, the most important optimization there is that something can be allocated on the stack instead of the heap, which is quite an optimization. EDIT: it does not actually have anything to do what you can stick in registers--at least nothing comes to my mind w/o thinking too hard about it... relevant papers directly from the hotspot-jvm are: -kotzmann, moessenboeck, "escape analysis in the context of dynamic compilation and deoptimization" http://www.usenix.org/events/vee05/full_papers/p111-kotzmann.pdf http://www.usenix.org/events/vee05/full_papers/p111-kotzmann... -kotzmann, moessenboeck: "run-time support for optimizations based on escape analysis" http://ftp.ssw.uni-linz.ac.at/Research/Papers/Ko07/Ko07.pdf http://ftp.ssw.uni-linz.ac.at/Research/Papers/Ko07/Ko07.pdf
- slava_pestov 17y ago
  Actually, once you've figured out that you can stack allocate an object, you can stick its instance variables in registers. This can be a huge win.
  - deleted 17y ago
    [deleted]

luke_s 17y ago

"The Java language does not offer any way to explicitly allocate an object on the stack, but this fact doesn't prevent JVMs from still using stack allocation where appropriate. JVMs can use a technique called escape analysis, by which they can tell that certain objects remain confined to a single thread for their entire lifetime, and that lifetime is bounded by the lifetime of a given stack frame. Such objects can be safely allocated on the stack instead of the heap. Even better, for small objects, the JVM can optimize away the allocation entirely and simply hoist the object's fields into registers." Taken from an IBM developerworks article here: http://www.ibm.com/developerworks/java/library/j-jtp09275.html http://www.ibm.com/developerworks/java/library/j-jtp09275.ht...