Expected performance difference between ConstantCallSite and unchanging MutableCallSite

[Charles Oliver Nutter]

Can I get a rough guesstimate from the JVM guys how much more overhead
is involved in accessing a never-changed MutableCallSite versus a
ConstantCallSite? I have a few places where I want to use
invokedynamic to lazily initialize some literals. They'll never change
after the initial construction, but I can't create them in the
bootstrap because I need the state they pass in (e.g. the
org.jruby.Ruby instance they're associated with). I'd like to bind a
constant method handle into the site after the first call and never
change it again.

- Charlie