6974928: G1: sometimes humongous objects are allocated in young regions

Summary: as the title says, sometimes we are allocating humongous objects in young regions and we shouldn't.
Reviewed-by: ysr, johnc

src/share/vm/gc_implementation/g1/g1CollectedHeap.cpp

@@ -2194,9 +2194,12 @@ size_t G1CollectedHeap::unsafe_max_tlab_alloc(Thread* ignored) const {
   }
 }
 
-HeapWord* G1CollectedHeap::allocate_new_tlab(size_t size) {
+HeapWord* G1CollectedHeap::allocate_new_tlab(size_t word_size) {
+  assert(!isHumongous(word_size),
+         err_msg("a TLAB should not be of humongous size, "
+                 "word_size = "SIZE_FORMAT, word_size));
   bool dummy;
-  return G1CollectedHeap::mem_allocate(size, false, true, &dummy);
+  return G1CollectedHeap::mem_allocate(word_size, false, true, &dummy);
 }
 
 bool G1CollectedHeap::allocs_are_zero_filled() {
@@ -3639,6 +3642,10 @@ void G1CollectedHeap::preserve_mark_if_necessary(oop obj, markOop m) {
 
 HeapWord* G1CollectedHeap::par_allocate_during_gc(GCAllocPurpose purpose,
                                                   size_t word_size) {
+  assert(!isHumongous(word_size),
+         err_msg("we should not be seeing humongous allocation requests "
+                 "during GC, word_size = "SIZE_FORMAT, word_size));
+
   HeapRegion* alloc_region = _gc_alloc_regions[purpose];
   // let the caller handle alloc failure
   if (alloc_region == NULL) return NULL;
@@ -3671,6 +3678,10 @@ G1CollectedHeap::allocate_during_gc_slow(GCAllocPurpose purpose,
                                          HeapRegion*    alloc_region,
                                          bool           par,
                                          size_t         word_size) {
+  assert(!isHumongous(word_size),
+         err_msg("we should not be seeing humongous allocation requests "
+                 "during GC, word_size = "SIZE_FORMAT, word_size));
+
   HeapWord* block = NULL;
   // In the parallel case, a previous thread to obtain the lock may have
   // already assigned a new gc_alloc_region.

src/share/vm/gc_implementation/g1/g1CollectedHeap.hpp

@@ -1032,7 +1032,7 @@ public:
   virtual bool supports_tlab_allocation() const;
   virtual size_t tlab_capacity(Thread* thr) const;
   virtual size_t unsafe_max_tlab_alloc(Thread* thr) const;
-  virtual HeapWord* allocate_new_tlab(size_t size);
+  virtual HeapWord* allocate_new_tlab(size_t word_size);
 
   // Can a compiler initialize a new object without store barriers?
   // This permission only extends from the creation of a new object

src/share/vm/gc_implementation/g1/g1CollectedHeap.inline.hpp

@@ -57,8 +57,9 @@ inline HeapWord* G1CollectedHeap::attempt_allocation(size_t word_size,
   assert( SafepointSynchronize::is_at_safepoint() ||
           Heap_lock->owned_by_self(), "pre-condition of the call" );
 
-  if (_cur_alloc_region != NULL) {
-
+  // All humongous allocation requests should go through the slow path in
+  // attempt_allocation_slow().
+  if (!isHumongous(word_size) && _cur_alloc_region != NULL) {
     // If this allocation causes a region to become non empty,
     // then we need to update our free_regions count.
 
@@ -69,13 +70,14 @@ inline HeapWord* G1CollectedHeap::attempt_allocation(size_t word_size,
     } else {
       res = _cur_alloc_region->allocate(word_size);
     }
-  }
-  if (res != NULL) {
-    if (!SafepointSynchronize::is_at_safepoint()) {
-      assert( Heap_lock->owned_by_self(), "invariant" );
-      Heap_lock->unlock();
+
+    if (res != NULL) {
+      if (!SafepointSynchronize::is_at_safepoint()) {
+        assert( Heap_lock->owned_by_self(), "invariant" );
+        Heap_lock->unlock();
+      }
+      return res;
     }
-    return res;
   }
   // attempt_allocation_slow will also unlock the heap lock when appropriate.
   return attempt_allocation_slow(word_size, permit_collection_pause);

src/share/vm/gc_implementation/g1/heapRegion.cpp

@@ -790,8 +790,18 @@ void HeapRegion::verify(bool allow_dirty,
   int objs = 0;
   int blocks = 0;
   VerifyLiveClosure vl_cl(g1, use_prev_marking);
+  bool is_humongous = isHumongous();
+  size_t object_num = 0;
   while (p < top()) {
     size_t size = oop(p)->size();
+    if (is_humongous != g1->isHumongous(size)) {
+      gclog_or_tty->print_cr("obj "PTR_FORMAT" is of %shumongous size ("
+                             SIZE_FORMAT" words) in a %shumongous region",
+                             p, g1->isHumongous(size) ? "" : "non-",
+                             size, is_humongous ? "" : "non-");
+       *failures = true;
+    }
+    object_num += 1;
     if (blocks == BLOCK_SAMPLE_INTERVAL) {
       HeapWord* res = block_start_const(p + (size/2));
       if (p != res) {
@@ -857,6 +867,13 @@ void HeapRegion::verify(bool allow_dirty,
     }
   }
 
+  if (is_humongous && object_num > 1) {
+    gclog_or_tty->print_cr("region ["PTR_FORMAT","PTR_FORMAT"] is humongous "
+                           "but has "SIZE_FORMAT", objects",
+                           bottom(), end(), object_num);
+    *failures = true;
+  }
+
   if (p != top()) {
     gclog_or_tty->print_cr("end of last object "PTR_FORMAT" "
                            "does not match top "PTR_FORMAT, p, top());