8036860: Pad and cache-align the BiasedMappedArray
Summary: Pad and cache-align BiasedMappedArray instances by default to avoid performance variability problems due to false sharing, as instances of this data structures are typically used for performance sensitive code.
Reviewed-by: brutisso, stefank
--- a/hotspot/src/share/vm/gc_implementation/g1/g1BiasedArray.cpp Mon Mar 17 10:07:51 2014 +0100
+++ b/hotspot/src/share/vm/gc_implementation/g1/g1BiasedArray.cpp Mon Mar 17 13:07:55 2014 +0100
@@ -24,6 +24,14 @@
#include "precompiled.hpp"
#include "gc_implementation/g1/g1BiasedArray.hpp"
+#include "memory/padded.inline.hpp"
+
+// Allocate a new array, generic version.
+address G1BiasedMappedArrayBase::create_new_base_array(size_t length, size_t elem_size) {
+ assert(length > 0, "just checking");
+ assert(elem_size > 0, "just checking");
+ return PaddedPrimitiveArray<u_char, mtGC>::create_unfreeable(length * elem_size);
+}
#ifndef PRODUCT
void G1BiasedMappedArrayBase::verify_index(idx_t index) const {
--- a/hotspot/src/share/vm/gc_implementation/g1/g1BiasedArray.hpp Mon Mar 17 10:07:51 2014 +0100
+++ b/hotspot/src/share/vm/gc_implementation/g1/g1BiasedArray.hpp Mon Mar 17 13:07:55 2014 +0100
@@ -25,8 +25,8 @@
#ifndef SHARE_VM_GC_IMPLEMENTATION_G1_G1BIASEDARRAY_HPP
#define SHARE_VM_GC_IMPLEMENTATION_G1_G1BIASEDARRAY_HPP
+#include "memory/allocation.hpp"
#include "utilities/debug.hpp"
-#include "memory/allocation.inline.hpp"
// Implements the common base functionality for arrays that contain provisions
// for accessing its elements using a biased index.
@@ -48,11 +48,7 @@
_bias(0), _shift_by(0) { }
// Allocate a new array, generic version.
- static address create_new_base_array(size_t length, size_t elem_size) {
- assert(length > 0, "just checking");
- assert(elem_size > 0, "just checking");
- return NEW_C_HEAP_ARRAY(u_char, length * elem_size, mtGC);
- }
+ static address create_new_base_array(size_t length, size_t elem_size);
// Initialize the members of this class. The biased start address of this array
// is the bias (in elements) multiplied by the element size.
--- a/hotspot/src/share/vm/memory/padded.hpp Mon Mar 17 10:07:51 2014 +0100
+++ b/hotspot/src/share/vm/memory/padded.hpp Mon Mar 17 13:07:55 2014 +0100
@@ -101,4 +101,12 @@
static T** create_unfreeable(uint rows, uint columns, size_t* allocation_size = NULL);
};
+// Helper class to create an array of T objects. The array as a whole will
+// start at a multiple of alignment and its size will be aligned to alignment.
+template <class T, MEMFLAGS flags, size_t alignment = DEFAULT_CACHE_LINE_SIZE>
+class PaddedPrimitiveArray {
+ public:
+ static T* create_unfreeable(size_t length);
+};
+
#endif // SHARE_VM_MEMORY_PADDED_HPP
--- a/hotspot/src/share/vm/memory/padded.inline.hpp Mon Mar 17 10:07:51 2014 +0100
+++ b/hotspot/src/share/vm/memory/padded.inline.hpp Mon Mar 17 13:07:55 2014 +0100
@@ -76,3 +76,13 @@
return result;
}
+
+template <class T, MEMFLAGS flags, size_t alignment>
+T* PaddedPrimitiveArray<T, flags, alignment>::create_unfreeable(size_t length) {
+ // Allocate a chunk of memory large enough to allow for some alignment.
+ void* chunk = AllocateHeap(length * sizeof(T) + alignment, flags);
+
+ memset(chunk, 0, length * sizeof(T) + alignment);
+
+ return (T*)align_pointer_up(chunk, alignment);
+}