--- old/src/share/vm/gc/g1/g1Allocator.cpp	2015-08-24 15:33:10.827670613 +0200
+++ new/src/share/vm/gc/g1/g1Allocator.cpp	2015-08-24 15:33:10.747668223 +0200
@@ -144,8 +144,12 @@
 HeapWord* G1Allocator::par_allocate_during_gc(InCSetState dest,
                                               size_t word_size,
                                               AllocationContext_t context) {
-  size_t temp;
-  return par_allocate_during_gc(dest, word_size, word_size, &temp, context);
+  size_t temp = 0;
+  HeapWord* result = par_allocate_during_gc(dest, word_size, word_size, &temp, context);
+  assert(result == NULL || temp == word_size,
+         err_msg("Requested " SIZE_FORMAT " words, but got " SIZE_FORMAT " at " PTR_FORMAT,
+                 word_size, temp, p2i(result)));
+  return result;
 }
 
 HeapWord* G1Allocator::par_allocate_during_gc(InCSetState dest,
@@ -264,12 +268,17 @@
     G1PLAB* alloc_buf = alloc_buffer(dest, context);
     alloc_buf->retire();
 
-    size_t actual_plab_size;
+    size_t actual_plab_size = 0;
     HeapWord* buf = _allocator->par_allocate_during_gc(dest,
                                                        required_in_plab,
                                                        plab_word_size,
                                                        &actual_plab_size,
                                                        context);
+
+    assert(buf == NULL || ((actual_plab_size >= required_in_plab) && (actual_plab_size <= plab_word_size)),
+           err_msg("Requested at minimum " SIZE_FORMAT ", desired " SIZE_FORMAT " words, but got " SIZE_FORMAT " at " PTR_FORMAT,
+                   required_in_plab, plab_word_size, actual_plab_size, p2i(buf)));
+
     if (buf != NULL) {
       alloc_buf->set_buf(buf, actual_plab_size);