9

So in the output of +LogCompilation there are messages printed

callee is too large

and 

too big

associated with specific methods (and the decision by the compiler not to inline).

But isn't the "callee" the method itself? What else could it mean? And if so, what's the difference between "callee too large" and "too big" - wouldn't they mean the same thing (maybe it's just a legacy log message, 2 engineers using different language for the same thing?)

Or is it possible that "callee" really means "caller"?
Either reason would be legitimate for not inlining. I'm a bit embarrassed that I don't understand this.

igaz
  • 392
  • 3
  • 9
  • I am not sure, but i would say, that inlining would make the caller to big... As for the "callee too large", it might refer to the inlined version being big, EG lots of arguments have to be prepared before and after inlined code... – Usagi Miyamoto Oct 01 '17 at 01:22
  • Well clearly inlining would make the caller *bigger* (whether "too big" would depend on a lot of factors). I'm asking why the 2 separate messages? Do they mean something different? – igaz Oct 01 '17 at 02:58

1 Answers1

11

HotSpot JVM has two JIT compilers: C1 and C2. They work together in Tiered mode (the default). The inlining strategy is not quite trivial, but the most simple factor is the size of the callee method in bytecodes.

  • "callee is too large" message is printed by C1 when the size in bytecodes of the method being inlined is larger than MaxInlineSize (35) multiplied by NestedInliningSizeRatio (90%) on each next level of inlining.
  • "too big" and "hot method too big" messages are printed by C2 when the size of the method being inlined is larger than MaxInlineSize (35) or FreqInlineSize (325) respectively.

So, both messages mean approximately the same, but on different tiers of compilation.

apangin
  • 92,924
  • 10
  • 193
  • 247