RFR: 8271461: CompileCommand support for hidden class methods [v2]

[Yi Yang]

On Fri, 30 Jul 2021 02:01:55 GMT, Jie Fu <jiefu at openjdk.org> wrote:

>> Hi all,
>> 
>> We'd like to improve the CompileCommand to support hidden class methods, which is helpful for debugging and perfmance analysis.
>> 
>> Current implementation of CompileCommand doesn't work for hidden class methods.
>> For example, if you run with `java -Xcomp -Xbatch -XX:+PrintCompilation`
>> The following hidden class methods were compiled:
>> 
>>    5317 1573    b  3       java.util.ResourceBundle$$Lambda$1/0x00000008010413c8::run (8 bytes)
>>    5318 1574    b  4       java.util.ResourceBundle$$Lambda$1/0x00000008010413c8::run (8 bytes)
>>    6735 1938    b  3       java.util.ResourceBundle$ResourceBundleProviderHelper$$Lambda$2/0x0000000801041e80::run (12 bytes)
>>    6736 1939    b  4       java.util.ResourceBundle$ResourceBundleProviderHelper$$Lambda$2/0x0000000801041e80::run (12 bytes)
>>    7060 2029    b  3       java.util.ResourceBundle$ResourceBundleProviderHelper$$Lambda$58/0x800000060::run (8 bytes)
>>    7061 2030    b  4       java.util.ResourceBundle$ResourceBundleProviderHelper$$Lambda$58/0x800000060::run (8 bytes)
>>    7688 2153    b  3       java.util.ResourceBundle$ResourceBundleProviderHelper$$Lambda$4/0x0000000801043218::run (16 bytes)
>>    7688 2154    b  4       java.util.ResourceBundle$ResourceBundleProviderHelper$$Lambda$4/0x0000000801043218::run (16 bytes)
>> 
>> 
>> Then people may want to exclude the compilation of `java.util.ResourceBundle$$Lambda$1/0x00000008010413c8::run` like this
>> 
>> -XX:CompileCommand=exclude,'java.util.ResourceBundle$$Lambda$1/0x00000008010413c8::run'
>> 
>> 
>> But unfortunately, it doesn't work.
>> 
>> CompileCommand: An error occurred during parsing
>> Error: Method pattern uses '/' together with '::'
>> Line: 'exclude,java.util.ResourceBundle$$Lambda$1/0x00000008010413c8::run'
>> 
>> Usage: '-XX:CompileCommand=<option>,<method pattern>' - to set boolean option to true
>> Usage: '-XX:CompileCommand=<option>,<method pattern>,<value>'
>> Use:   '-XX:CompileCommand=help' for more information and to list all option.
>> 
>> 
>> The failing reason is that the name of `java.util.ResourceBundle$$Lambda$1/0x00000008010413c8::run` is actually `java.util.ResourceBundle$$Lambda$1+0x00000008010413c8::run` in the VM.
>> But "+" had been replaced with "/" when it was printed by PrintCompilation [1].
>> 
>> So for a hidden class method, "/" should be replaced with "+" to make CompileCommand work.
>> 
>> Thanks.
>> Best regards,
>> Jie
>> 
>> 
>> [1] https://github.com/openjdk/jdk/blob/master/src/hotspot/share/oops/klass.cpp#L685
>
> Jie Fu has updated the pull request incrementally with one additional commit since the last revision:
> 
>   Use isdigit

At JDK level, the generated class name depends on a counter:(`Test$$Lambda$215`)

https://github.com/openjdk/jdk/blob/4f42eb6601c3b6011d3c2b30af6b2be264ff7c0e/src/java.base/share/classes/java/lang/invoke/InnerClassLambdaMetafactory.java#L207-L214

Later, class file parser mangles this class name:(`Test$$Lambda$215+0x0000000801144200`)
https://github.com/openjdk/jdk/blob/4f42eb6601c3b6011d3c2b30af6b2be264ff7c0e/src/hotspot/share/classfile/classFileParser.cpp#L5910-L5933

When we want to print this class name, we will replace '+' with '/':(`Test$$Lambda$215/0x0000000801144200`)
https://github.com/openjdk/jdk/blob/4f42eb6601c3b6011d3c2b30af6b2be264ff7c0e/src/hotspot/share/oops/klass.cpp#L665-L694

I don't fully practice what I see but it looks like the class name depends on class loading, there is no reliable way to ensure the same class loading order from run to run.


import java.util.ArrayList;
import java.util.HashMap;
import java.util.Random;

public class Test {
    static class Foo {
    }

    public static void main(String args[]) {
        for (int i = 0; i < 100000; i++) {
            test0();
            if (new Random().nextInt(50) > 25) {
                new Foo(); // class loading, -Xlog:class+load
            }
            test2();
        }
    }

    static void test0() {
        doit(() -> {
        });
    }

    static void test2() {
        doit(() -> {
        });
    }

    static void doit(Runnable r) {
        r.run();
    }
}



[9.716s][info][class,load] Test source: file:/home/qingfeng.yy/jdktip/mytest/Lambda.java
[9.724s][info][class,load] Test$$Lambda$216/0x0000000801144200 source: Test
[9.730s][info][class,load] java.util.random.RandomGenerator source: shared objects file
[9.732s][info][class,load] java.util.Random source: shared objects file
[9.745s][info][class,load] Test$Foo source: file:/home/qingfeng.yy/jdktip/mytest/Lambda.java
[9.751s][info][class,load] Test$$Lambda$217/0x0000000801144618 source: Test


[9.933s][info][class,load] Test source: file:/home/qingfeng.yy/jdktip/mytest/Lambda.java
[9.940s][info][class,load] Test$$Lambda$216/0x0000000801144200 source: Test
[9.946s][info][class,load] java.util.random.RandomGenerator source: shared objects file
[9.949s][info][class,load] java.util.Random source: shared objects file
[9.962s][info][class,load] Test$$Lambda$217/0x0000000801144418 source: Test
[9.968s][info][class,load] Test$Foo source: file:/home/qingfeng.yy/jdktip/mytest/Lambda.java

-------------

PR: https://git.openjdk.java.net/jdk/pull/4926