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src/share/vm/gc/g1/g1Allocator.cpp

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rev 8813 : imported patch 8003237-no-wait-for-free-list
rev 8814 : imported patch jon-fast-evac-failure
rev 8815 : [mq]: bengt-jon-more-naming
rev 8818 : imported patch 8073013-add-detailed-information-about-plab-memory-usage
rev 8819 : imported patch jon-review-statistics
rev 8828 : imported patch 8067339-PLAB-reallocation-might-result-in-failure-to-allocate

@@ -221,27 +221,39 @@
   for (size_t i = 0; i < ARRAY_SIZE(_direct_allocated); i++) {
     _direct_allocated[i] = 0;
   }
 }
 
+bool G1PLABAllocator::may_throw_away_buffer(size_t const allocation_word_sz, size_t const buffer_size) const {
+  return (allocation_word_sz * 100 < buffer_size * ParallelGCBufferWastePct);
+}
+
 HeapWord* G1PLABAllocator::allocate_direct_or_new_plab(InCSetState dest,
                                                        size_t word_sz,
                                                        AllocationContext_t context,
                                                        bool* plab_refill_failed) {
-  size_t gclab_word_size = _g1h->desired_plab_sz(dest);
-  if (word_sz * 100 < gclab_word_size * ParallelGCBufferWastePct) {
+  size_t plab_word_size = G1CollectedHeap::heap()->desired_plab_sz(dest);
+  size_t required_in_plab = word_sz + PLAB::alignment_reserve();
+
+  // Only get a new PLAB if the allocation fits and it would not waste more than
+  // ParallelGCBufferWastePct in the existing buffer.
+  if ((required_in_plab <= plab_word_size) &&
+    may_throw_away_buffer(required_in_plab, plab_word_size)) {
+
     G1PLAB* alloc_buf = alloc_buffer(dest, context);
     alloc_buf->retire();
 
-    HeapWord* buf = _allocator->par_allocate_during_gc(dest, gclab_word_size, context);
+    HeapWord* buf = _allocator->par_allocate_during_gc(dest, plab_word_size, context);
     if (buf != NULL) {
       // Otherwise.
-      alloc_buf->set_word_size(gclab_word_size);
+      alloc_buf->set_word_size(plab_word_size);
       alloc_buf->set_buf(buf);
 
       HeapWord* const obj = alloc_buf->allocate(word_sz);
-      assert(obj != NULL, "buffer was definitely big enough...");
+      assert(obj != NULL, err_msg("PLAB should have been big enough, tried to allocate "
+                                  SIZE_FORMAT " with alignment reserve " SIZE_FORMAT " PLAB size " SIZE_FORMAT,
+                                  word_sz, PLAB::alignment_reserve(), plab_word_size));
       return obj;
     }
     // Otherwise.
     *plab_refill_failed = true;
   }
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