[GR-32941] Allocate TLABs from chunks instead of as chunks

[graalvmbot]

Having each allocating thread hold on to an entire aligned chunk becomes a problem when there are many allocating threads, and inflates the heap when the threads rarely allocate and allocate mostly small objects. We should allocate TLAB ranges out of aligned chunks, sized according to the number of allocating threads and expected refills between collections.

[roberttoyonaga]

Hi, this is great! Just a few questions:

Is it the case that this change tries to reduce the overall memory usage (by allowing TLABS to share heap chunks) but will not actually affect the frequency that the slow path is taken?

Am I correct in understanding that even when a new TLAB is able to be created without allocating a new heap chunk there is still contention when making space in the current heap chunk?

There is no dynamic resizing of TLABS, whenever more space is required, the old TLAB must be retired and a new one (with a different) size is created, or allocation is done directly on the heap?