What's the best way to append an oop to a GrowableArray?

Ioi Lam ioi.lam at oracle.com
Thu Nov 29 05:56:06 UTC 2018

I have a memory model question:

I need to create lots of objects and append them into a GrowableArray

    GrowableArray<oop>* arr = new (ResourceObj::C_HEAP, mtInternal)
         GrowableArray<oop>(10000, true);;

    void doit() {
        while (...) {
            oop o = allocate_from_heap(.....);

There is only a single thread that can append to the array, so I am not 
using any locks.

However, GC could happen inside this loop, so I have written a do_oops() 
function that would scan the array during GC. (For convenience, I am 
calling my_oops_do() from within SystemDictionary:oops_do() for now ...).

    void my_oops_do(OopClosure* f) {
         int len = arr->length();
         for (int i = 0; i < len; i++) {

This seems to work fine on my dual socket Xeon, but will it work 
everywhere? Do I need to do anything to ensure that the GC threads can 
read the up-to-date values of the array elements, and the array length?

- Ioi

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