P4
There seems to be different ways of handling scavengeable nmethod roots in hotspot.
The primary way of dealing with them is to use the CodeCache scavenge root nmethod list that maintains a list of all nmethods with scavengeable nmethods.
However, G1 does not use this list as it has its own mechanism of keeping track of nmethods with scavengeable roots pointing into the heap.
To handle this, the current CodeCache code is full of special cases for G1. In multiple cases we check if (UseG1GC) and then return.
We seemingly need a better way of communicating to the GC what scavengeable nmethod roots there are.
The primary way of dealing with them is to use the CodeCache scavenge root nmethod list that maintains a list of all nmethods with scavengeable nmethods.
However, G1 does not use this list as it has its own mechanism of keeping track of nmethods with scavengeable roots pointing into the heap.
To handle this, the current CodeCache code is full of special cases for G1. In multiple cases we check if (UseG1GC) and then return.
We seemingly need a better way of communicating to the GC what scavengeable nmethod roots there are.