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.
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? 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. Running "java -Xint -Xtrace:interpreter Hello" then also gave me way more output then I expected. For example ... interpreter: java/lang/String indexOf(II)I interpreter: java/lang/String startsWith(Ljava/lang/String;)Z interpreter: java/lang/String startsWith(Ljava/lang/String;I)Z interpreter: java/lang/String regionMatches(ILjava/lang/String;II)Z interpreter: java/net/URI access$1002(Ljava/net/URI;Ljava/lang/String;)Ljava/lang/String; interpreter: java/net/URI access$1000(Ljava/net/URI;)Ljava/lang/String; interpreter: java/net/URI$Helper validatePath(Ljava/lang/String;Ljava/lang/String;I)V interpreter: java/net/URIEncoderDecoder validate(Ljava/lang/String;Ljava/lang/String;)V interpreter: java/lang/String length()I interpreter: java/lang/String charAt(I)C interpreter: java/lang/String indexOf(I)I interpreter: java/lang/String indexOf(II)I interpreter: java/lang/String length()I ... I'm not sure why all of this is being interpreted for a simple hello world program. My understanding was that the interpreter traverses the byte code for the given input and then handles the executed byte codes. It seems like a lot more is going on here. 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? Thanks Armand
