8357570: [macOS] os::Bsd::available_memory() might return too low values

Reviewed-by: clanger, mdoerr, lucy

Author: MBaesken

src/hotspot/os/bsd/os_bsd.cpp

@@ -154,7 +154,8 @@ julong os::Bsd::available_memory() {
   assert(kerr == KERN_SUCCESS,
          "host_statistics64 failed - check mach_host_self() and count");
   if (kerr == KERN_SUCCESS) {
-    available = vmstat.free_count * os::vm_page_size();
+    // free_count is just a lowerbound, other page categories can be freed too and make memory available
+    available = (vmstat.free_count + vmstat.inactive_count + vmstat.purgeable_count) * os::vm_page_size();
   }
 #endif
   return available;