which jvm?
On Sat, Feb 5, 2022 at 6:26 AM r r <[email protected]> wrote:
> Hello,
> we know that there are some techniques that make virtual calls not so
> expensive in JVM like Inline Cache or Polymorphic Inline Cache.
>
> Let's consider the following situation:
>
> Base is an interface.
>
> public void f(Base[] b) {
> for(int i = 0; i < b.length; i++) {
> b[i].m();
> }
> }
>
> I see from my profiler that calling virtual (interface) method m is
> relatively expensive.
> f is on the hot path and it was compiled to machine code (C2) but I see
> that call to m is a real virtual call. It means that it was not optimised
> by JVM.
>
> The question is, how to deal with a such situation? Obviously, I cannot
> make the method m not virtual here because it requires a serious
> redesign.
>
> Can I do anything or I have to accept it? I was thinking how to "force" or
> "convince" a JVM to
>
> 1. use polymorphic inline cache here - the number of different types in b
> is quite low - between 4-5 types.
> 2. to unroll this loop - length of b is also relatively small. After an
> unroll it is possible that Inline Cache will be helpful here.
>
> Thanks in advance for any advices.
> Regards,
>
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