Loopy CallSite

[Remi Forax]

On 07/16/2014 07:38 PM, Vladimir Ivanov wrote:
> Remi,
>
> The problem is that for every iteration you create new call site
> >      for(int i=0; i<100_000; i++) {
> >        new LoopyCS().getTarget().invokeExact(1_000);
> >      }
>
> In LoopyCS constructor you instantiates 3 new MethodHandles:
> >        target = MethodHandles.filterArguments(target, 0, FOO);
> >        target = MethodHandles.guardWithTest(ZERO,
> >            target,
> > MethodHandles.dropArguments(MethodHandles.constant(int.class,
> > 0).asType(MethodType.methodType(void.class)), 0, int.class));
>
> Since we don't cache LambdaForms yet for these combinators, 3 new 
> LambdaForms are created for each invocation. Then they are compiled to 
> bytecode and then JIT kicks in. That's why you see continuous JITing.
>
> If you reuse a call site object, it stabilizes very quickly.

doh, sorry for this stupid code :(

>
> Best regards,
> Vladimir Ivanov

Rémi

>
> On 7/12/14 6:05 PM, Remi Forax wrote:
>> It seems that the JIT is lost with whe there is a loopy callsite and
>> never stabilize (or the steady state is after the program ends).
>>
>> import java.lang.invoke.MethodHandle;
>> import java.lang.invoke.MethodHandles;
>> import java.lang.invoke.MethodType;
>> import java.lang.invoke.MutableCallSite;
>>
>> public class Loop {
>>    static class LoopyCS extends MutableCallSite {
>>      public LoopyCS() {
>>        super(MethodType.methodType(void.class, int.class));
>>
>>        MethodHandle target = dynamicInvoker();
>>        target = MethodHandles.filterArguments(target, 0, FOO);
>>        target = MethodHandles.guardWithTest(ZERO,
>>            target,
>> MethodHandles.dropArguments(MethodHandles.constant(int.class,
>> 0).asType(MethodType.methodType(void.class)), 0, int.class));
>>        setTarget(target);
>>      }
>>    }
>>
>>    static final MethodHandle FOO, ZERO;
>>    static {
>>      try {
>>        FOO = MethodHandles.lookup().findStatic(Loop.class, "foo",
>> MethodType.methodType(int.class, int.class));
>>        ZERO = MethodHandles.lookup().findStatic(Loop.class, "zero",
>> MethodType.methodType(boolean.class, int.class));
>>      } catch (NoSuchMethodException | IllegalAccessException e) {
>>        throw new AssertionError(e);
>>      }
>>    }
>>
>>    private static boolean zero(int i) {
>>      return i != 0;
>>    }
>>
>>    private static int foo(int i) {
>>      COUNTER++;
>>      return i - 1;
>>    }
>>
>>    private static int COUNTER = 0;
>>
>>    public static void main(String[] args) throws Throwable {
>>      for(int i=0; i<100_000; i++) {
>>        new LoopyCS().getTarget().invokeExact(1_000);
>>      }
>>      System.out.println(COUNTER);
>>    }
>> }
>>
>> cheers,
>> Rémi
>>
>>
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