Running very small programs on very small heaps (~10 M) that have a relatively large allocation rate, G1 struggles a bit with 1M region sizes: there are a fair amount of allocation failures and even full gcs caused by fragmentation/heap sizing decisions.

E.g. on dacapo 23.11 Avrora at 14M heap, selecting smaller heap regions (256k) reduces total pause time from <2% to <0.5% of execution time.

Improve region sizes to better balance heap size vs. humongous object allocation issues due to fragmentation.

A more interesting case for this could be in context of JDK-8359802.