again on megamorphic problems

[Attila Szegedi]

I will just toot my own horn and say that Dynalink handles this - Nashorn
actually leverages this feature to detect megamorphic sites and relink them
differently. Dynalink keeps track of number of times a call site is
relinked, and if it reaches a configurable threshold [1], it'll start
returning true in "isCallSiteUnstable" [2] method in the link requests it
sends to the linkers, who are then at a discretion to create different
linkage - supposedly something more generic that might be less efficient
than any individual narrow linkage, but wins in the end as it's more stable
and avoids further relinking.

Attila.

[1]
https://github.com/szegedi/dynalink/blob/master/src/main/java/org/dynalang/dynalink/DynamicLinkerFactory.java#L169
[2]
https://github.com/szegedi/dynalink/blob/master/src/main/java/org/dynalang/dynalink/linker/LinkRequest.java#L59


On Thu, Dec 20, 2012 at 2:10 PM, Jochen Theodorou <blackdrag at gmx.org> wrote:

> Hi,
>
> let us assume the following example... I have a method foo
>
> public Object foo(Object arg){return bar(arg)}
>
> nothing fancy, quite simple... and let us assume foo is called from
> dozens of places with differing argument types.
>
> If I understood right, then the call site in foo will become
> megamorphic, making it impossible to inline bar into the place from
> where foo is called. foo becomes like a inlining barrier so to say.
>
> The question is now more or less, if I can avoid that problem with
> MethodHandles. I mean the pattern should occur with lamdas more than
> once and I am wondering if there is anything planed to do against this
> or if there has been already done something, or well, if I can bypass
> the problem in indy.
>
> bye Jochen
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