Welcome Armand! My comments are inlined. On 10/23/06, Armand Navabi <[EMAIL PROTECTED]> wrote:
I am trying to become more familiar with the jit code. I ran the following to see what all was compiled when running Hello World. "java -Xtrace:compile Hello". I was very surprised to see the number of methods that seem to be loaded. I think there are about 1079 methods that get compiled for Hello World.
Yes you are right. To run Hello World application ~ 1000 methods are compiled. These methods are from threads, IO, classloading, security, utilities, VM infrastructure classes. 1000 methods is not a big number: the optimizing compiler performance is more than 1000/per second (my 2Ghz PC). The baseline JET compiler is ten times faster. Does harmony just load all the classes in the classlib and compile every
method? If not, then why would there be so many methods compiled for a simple hello world program?
Not Harmony does not load all the classes. Right now I am trying to write a simple profiling tool that counts the
number of certain instructions in a program for a given input (i.e. I want to run the program, and for every instruction that ends up running, collect information). So, since it seems that the jit not only compiles every instruction in the program (not only the ones that end up running), but also a bunch of other classes, I thought perhaps I would be more interested in the interpreter.
Interpreter also executes a lot of "startup methods" before running "main". There is a solution how to compile only predefined set of methods by separate JIT compiler. See EM guide for details how to filter methods: http://incubator.apache.org/harmony/subcomponents/drlvm/emguide.html The filters will not work with interpreter. Also, I am trying to become familiar with the jit and interpreter by
reading the DRL Developer's Guide. Are there any other resources other than the Developer's Guide and this mailing list?
Check these pages too: http://incubator.apache.org/harmony/subcomponents/drlvm/index.html http://wiki.apache.org/harmony/ or ask directly in the mailing list :) -- Mikhail Fursov
