Memory allocation being a bottleneck in high-performance applications? I'm not sure what your "high-performance" means (HPC? Games?), but profile an application without garbage collection and 80% of the time a significant part of the run time will be within malloc and free.

A garbage collector might even be more efficient, since it can delay/avoid the management. When will a GC actually do a collection run? At the moment, when it cannot provide an allocation request from its pool. A program which needs little memory might never hit this barrier. This is like a never calling 'free'. Of course, whether this can be done can only be decided at runtime.

There is nothing in a garbage collector which prevents alignments to cache boundaries, preallocation, or stack allocation. In the case of Java the Hotspot JVM can allocate objects on the stack. However, this is a compiler optimization in this case and cannot be directly controlled by the programmer. The upside is that the programmer cannot introduce memory bugs.

If you write a game with Java you can allocate a fixed size of memory up front as well. I do not see a problem with garbage collection here.