8322278: Generational ZGC: Adjust the comment of ZHeuristics::use_per…

…_cpu_shared_small_pages

Reviewed-by: eosterlund

src/hotspot/share/gc/z/zHeuristics.cpp

@@ -60,8 +60,8 @@ size_t ZHeuristics::relocation_headroom() {
 }
 
 bool ZHeuristics::use_per_cpu_shared_small_pages() {
-  // Use per-CPU shared small pages only if these pages occupy at most 3.125%
-  // of the max heap size. Otherwise fall back to using a single shared small
+  // Use per-CPU shared small pages only if these pages don't have a significant
+  // heap overhead. Otherwise fall back to using a single shared small
   // page. This is useful when using small heaps on large machines.
   const size_t per_cpu_share = significant_heap_overhead() / ZCPU::count();
   return per_cpu_share >= ZPageSizeSmall;