Wasm: LOH objects seem to consume more memory than expected

[yowl]

The following code results in emscripten running out of memory

        var mr = new MiniRandom(257);
        var keptObjects = new object[1000];
        for (var i = 0; i < 1000000; i++)
        {
            var r = mr.Next();
            object o;
            o = new long[20000]; // large object heap, 160000 > 85KB
            keptObjects[r % 1000] = o;
        }

This should only be around 160,012,000 bytes, but it appears to go over 2GB

emscripten_realloc_buffer: Attempted to grow heap from 2130444288 bytes to 2147483648 bytes, but got error: RangeError: WebAssembly.Memory.grow(): Maximum memory size exceeded
emscripten_realloc_buffer: Attempted to grow heap from 2130444288 bytes to 2147483648 bytes, but got error: RangeError: WebAssembly.Memory.grow(): Maximum memory size exceeded
emscripten_realloc_buffer: Attempted to grow heap from 2130444288 bytes to 2147483648 bytes, but got error: RangeError: WebAssembly.Memory.grow(): Maximum memory size exceeded
Failed to grow the heap from 2130444288 bytes to 2147483648 bytes, not enough memory!
emscripten_realloc_buffer: Attempted to grow heap from 2130444288 bytes to 2147483648 bytes, but got error: RangeError: WebAssembly.Memory.grow(): Maximum memory size exceeded
emscripten_realloc_buffer: Attempted to grow heap from 2130444288 bytes to 2147483648 bytes, but got error: RangeError: WebAssembly.Memory.grow(): Maximum memory size exceeded
emscripten_realloc_buffer: Attempted to grow heap from 2130444288 bytes to 2147483648 bytes, but got error: RangeError: WebAssembly.Memory.grow(): Maximum memory size exceeded
Failed to grow the heap from 2130444288 bytes to 2147483648 bytes, not enough memory!
Assertion failed: ret == 0, at: E:\GitHub\corert\src\Native\gc\unix\gcenv.unix.cpp,627,VirtualReserveInner
exception thrown: RuntimeError: abort(Assertion failed: ret == 0, at: E:\GitHub\corert\src\Native\gc\unix\gcenv.unix.cpp,627,VirtualReserveInner) at Error
    at jsStackTrace (E:\github\corert\tests\src\Simple\HelloWasm\bin\Debug\wasm\native\HelloWasm.js:2079:19)
    at stackTrace (E:\github\corert\tests\src\Simple\HelloWasm\bin\Debug\wasm\native\HelloWasm.js:2096:16)
    at abort (E:\github\corert\tests\src\Simple\HelloWasm\bin\Debug\wasm\native\HelloWasm.js:1796:44)
    at ___assert_fail (E:\github\corert\tests\src\Simple\HelloWasm\bin\Debug\wasm\native\HelloWasm.js:2570:7)
    at VirtualReserveInner(unsigned long, unsigned long, unsigned int, unsigned int) (wasm-function[22264]:0x105b320)
    at GCToOSInterface::VirtualReserve(unsigned long, unsigned long, unsigned int, unsigned short) (wasm-function[22263]:0x105b01e)
    at WKS::gc_heap::grow_brick_card_tables(unsigned char*, unsigned char*, unsigned long, WKS::heap_segment*, WKS::gc_heap*, int) (wasm-function[21342]:0xf6aee1)
    at WKS::gc_heap::get_segment(unsigned long, WKS::gc_oh_num) (wasm-function[21321]:0xf6661c)
    at WKS::gc_heap::get_segment_for_uoh(int, unsigned long) (wasm-function[21358]:0xf6cc33)
    at WKS::gc_heap::get_uoh_segment(int, unsigned long, int*) (wasm-function[21360]:0xf6d7b0),RuntimeError: abort(Assertion failed: ret == 0, at: E:\GitHub\corert\src\Native\gc\unix\gcenv.unix.cpp,627,VirtualReserveInner) at Error
    at jsStackTrace (E:\github\corert\tests\src\Simple\HelloWasm\bin\Debug\wasm\native\HelloWasm.js:2079:19)
    at stackTrace (E:\github\corert\tests\src\Simple\HelloWasm\bin\Debug\wasm\native\HelloWasm.js:2096:16)
    at abort (E:\github\corert\tests\src\Simple\HelloWasm\bin\Debug\wasm\native\HelloWasm.js:1796:44)
    at ___assert_fail (E:\github\corert\tests\src\Simple\HelloWasm\bin\Debug\wasm\native\HelloWasm.js:2570:7)
    at VirtualReserveInner(unsigned long, unsigned long, unsigned int, unsigned int) (wasm-function[22264]:0x105b320)
    at GCToOSInterface::VirtualReserve(unsigned long, unsigned long, unsigned int, unsigned short) (wasm-function[22263]:0x105b01e)
    at WKS::gc_heap::grow_brick_card_tables(unsigned char*, unsigned char*, unsigned long, WKS::heap_segment*, WKS::gc_heap*, int) (wasm-function[21342]:0xf6aee1)
    at WKS::gc_heap::get_segment(unsigned long, WKS::gc_oh_num) (wasm-function[21321]:0xf6661c)
    at WKS::gc_heap::get_segment_for_uoh(int, unsigned long) (wasm-function[21358]:0xf6cc33)
    at WKS::gc_heap::get_uoh_segment(int, unsigned long, int*) (wasm-function[21360]:0xf6d7b0)
    at abort (E:\github\corert\tests\src\Simple\HelloWasm\bin\Debug\wasm\native\HelloWasm.js:1802:11)
    at ___assert_fail (E:\github\corert\tests\src\Simple\HelloWasm\bin\Debug\wasm\native\HelloWasm.js:2570:7)
    at VirtualReserveInner(unsigned long, unsigned long, unsigned int, unsigned int) (wasm-function[22264]:0x105b320)
    at GCToOSInterface::VirtualReserve(unsigned long, unsigned long, unsigned int, unsigned short) (wasm-function[22263]:0x105b01e)
    at WKS::gc_heap::grow_brick_card_tables(unsigned char*, unsigned char*, unsigned long, WKS::heap_segment*, WKS::gc_heap*, int) (wasm-function[21342]:0xf6aee1)
    at WKS::gc_heap::get_segment(unsigned long, WKS::gc_oh_num) (wasm-function[21321]:0xf6661c)
    at WKS::gc_heap::get_segment_for_uoh(int, unsigned long) (wasm-function[21358]:0xf6cc33)
    at WKS::gc_heap::get_uoh_segment(int, unsigned long, int*) (wasm-function[21360]:0xf6d7b0)
    at WKS::gc_heap::uoh_get_new_seg(int, unsigned long, int*, oom_reason*) (wasm-function[21549]:0xf9b385)
    at WKS::gc_heap::allocate_uoh(int, unsigned long, alloc_context*, unsigned int, int) (wasm-function[21553]:0xf9d6dc)

If the large arrays are not stored then this code completes, so it appears collection is at least occurring sometimes.