query on properties in /system/build.prop

Question

Could some one please explain me regarding the below properties in build.prop,

dalvik.vm.heapstartsize=5m
dalvik.vm.heapgrowthlimit=48m
dalvik.vm.heapsize=128m
dalvik.vm.heaptargetutilization=0.75
dalvik.vm.heapminfree=512k
dalvik.vm.heapmaxfree=2m

Thanks for your help.

Answer 1

Walking through the list:

dalvik.vm.heapstartsize=5m

This is converted to a -Xms option for Dalvik. It specifies the initial size of the managed heap.

dalvik.vm.heapsize=128m

This is converted to a -Xmx option for Dalvik. It specifies the maximum size of the managed heap.

dalvik.vm.heapgrowthlimit=48m

This converts to a -XX:HeapGrowthLimit option. It specifies the maximum size of a "standard" app's heap. If the app uses android:largeHeap in its manifest, it uses the full heapsize value instead.

dalvik.vm.heaptargetutilization=0.75

This converts to a -XX:HeapTargetUtilization option. It gives the VM a hint as to how full the managed heap should be allowed to become.

dalvik.vm.heapminfree=512k
dalvik.vm.heapmaxfree=2m

These converts to -XX:HeapMinFree and -XX:HeapMaxFree, respectively. These are used in conjunction with the the XX:HeapTargetUtilization to determine how much to grow the heap when the heap needs to grow.

For more details, see the HeapSource sources.