src/hotspot/share/gc/epsilon/epsilonHeap.cpp

rev 52116 : 8212177: Epsilon alignment adjustments can overflow max TLAB size
Reviewed-by: XXX

*** 45,55 ****
  
    _space = new ContiguousSpace();
    _space->initialize(committed_region, /* clear_space = */ true, /* mangle_space = */ true);
  
    // Precompute hot fields
!   _max_tlab_size = MIN2(CollectedHeap::max_tlab_size(), EpsilonMaxTLABSize / HeapWordSize);
    _step_counter_update = MIN2<size_t>(max_byte_size / 16, EpsilonUpdateCountersStep);
    _step_heap_print = (EpsilonPrintHeapSteps == 0) ? SIZE_MAX : (max_byte_size / EpsilonPrintHeapSteps);
    _decay_time_ns = (int64_t) EpsilonTLABDecayTime * NANOSECS_PER_MILLISEC;
  
    // Enable monitoring
--- 45,55 ----
  
    _space = new ContiguousSpace();
    _space->initialize(committed_region, /* clear_space = */ true, /* mangle_space = */ true);
  
    // Precompute hot fields
!   _max_tlab_size = MIN2(CollectedHeap::max_tlab_size(), align_object_size(EpsilonMaxTLABSize / HeapWordSize));
    _step_counter_update = MIN2<size_t>(max_byte_size / 16, EpsilonUpdateCountersStep);
    _step_heap_print = (EpsilonPrintHeapSteps == 0) ? SIZE_MAX : (max_byte_size / EpsilonPrintHeapSteps);
    _decay_time_ns = (int64_t) EpsilonTLABDecayTime * NANOSECS_PER_MILLISEC;
  
    // Enable monitoring
*** 215,224 ****
--- 215,234 ----
    size = MAX2(min_size, MIN2(_max_tlab_size, size));
  
    // Always honor alignment
    size = align_up(size, MinObjAlignment);
  
+   // Check that adjustments did not break local and global invariants
+   assert(is_object_aligned(size),
+          "Size honors object alignment: " SIZE_FORMAT, size);
+   assert(min_size <= size,
+          "Size honors min size: "  SIZE_FORMAT " <= " SIZE_FORMAT, min_size, size);
+   assert(size <= _max_tlab_size,
+          "Size honors max size: "  SIZE_FORMAT " <= " SIZE_FORMAT, size, _max_tlab_size);
+   assert(size <= CollectedHeap::max_tlab_size(),
+          "Size honors global max size: "  SIZE_FORMAT " <= " SIZE_FORMAT, size, CollectedHeap::max_tlab_size());
+ 
    if (log_is_enabled(Trace, gc)) {
      ResourceMark rm;
      log_trace(gc)("TLAB size for \"%s\" (Requested: " SIZE_FORMAT "K, Min: " SIZE_FORMAT
                            "K, Max: " SIZE_FORMAT "K, Ergo: " SIZE_FORMAT "K) -> " SIZE_FORMAT "K",
                    thread->name(),