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.
Best regards,
Vladimir Ivanov
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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