8221732: Introduce CollectedHeap::hash_oop()

Reviewed-by: kbarrett, tschatzl, stefank

src/hotspot/share/gc/shared/collectedHeap.cpp

@@ -575,3 +575,8 @@ void CollectedHeap::deduplicate_string(oop str) {
 size_t CollectedHeap::obj_size(oop obj) const {
   return obj->size();
 }
+
+uint32_t CollectedHeap::hash_oop(oop obj) const {
+  const uintptr_t addr = cast_from_oop<uintptr_t>(obj);
+  return static_cast<uint32_t>(addr >> LogMinObjAlignment);
+}

src/hotspot/share/gc/shared/collectedHeap.hpp

@@ -239,6 +239,8 @@ class CollectedHeap : public CHeapObj<mtInternal> {
 
   DEBUG_ONLY(bool is_in_or_null(const void* p) const { return p == NULL || is_in(p); })
 
+  virtual uint32_t hash_oop(oop obj) const;
+
   void set_gc_cause(GCCause::Cause v) {
      if (UsePerfData) {
        _gc_lastcause = _gc_cause;

src/hotspot/share/gc/z/zCollectedHeap.cpp

@@ -110,6 +110,10 @@ bool ZCollectedHeap::is_in(const void* p) const {
   return is_in_reserved(p) && _heap.is_in((uintptr_t)p);
 }
 
+uint32_t ZCollectedHeap::hash_oop(oop obj) const {
+  return _heap.hash_oop(obj);
+}
+
 HeapWord* ZCollectedHeap::allocate_new_tlab(size_t min_size, size_t requested_size, size_t* actual_size) {
   const size_t size_in_bytes = ZUtils::words_to_bytes(align_object_size(requested_size));
   const uintptr_t addr = _heap.alloc_tlab(size_in_bytes);

src/hotspot/share/gc/z/zCollectedHeap.hpp

@@ -73,6 +73,8 @@ public:
   virtual bool is_maximal_no_gc() const;
   virtual bool is_in(const void* p) const;
 
+  virtual uint32_t hash_oop(oop obj) const;
+
   virtual HeapWord* mem_allocate(size_t size, bool* gc_overhead_limit_was_exceeded);
   virtual MetaWord* satisfy_failed_metadata_allocation(ClassLoaderData* loader_data,
                                                        size_t size,

src/hotspot/share/gc/z/zHeap.hpp

@@ -103,6 +103,7 @@ public:
   size_t unsafe_max_tlab_alloc() const;
 
   bool is_in(uintptr_t addr) const;
+  uint32_t hash_oop(oop obj) const;
 
   // Block
   uintptr_t block_start(uintptr_t addr) const;

src/hotspot/share/gc/z/zHeap.inline.hpp

@@ -27,6 +27,7 @@
 #include "gc/z/zAddress.inline.hpp"
 #include "gc/z/zForwarding.inline.hpp"
 #include "gc/z/zForwardingTable.inline.hpp"
+#include "gc/z/zHash.inline.hpp"
 #include "gc/z/zHeap.hpp"
 #include "gc/z/zMark.inline.hpp"
 #include "gc/z/zOop.inline.hpp"
@@ -44,6 +45,11 @@ inline ReferenceDiscoverer* ZHeap::reference_discoverer() {
   return &_reference_processor;
 }
 
+inline uint32_t ZHeap::hash_oop(oop obj) const {
+  const uintptr_t offset = ZAddress::offset(ZOop::to_address(obj));
+  return ZHash::address_to_uint32(offset);
+}
+
 inline bool ZHeap::is_object_live(uintptr_t addr) const {
   ZPage* page = _page_table.get(addr);
   return page->is_object_live(addr);

src/hotspot/share/prims/jvmtiTagMap.cpp

@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2003, 2018, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 2003, 2019, Oracle and/or its affiliates. All rights reserved.
  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
  *
  * This code is free software; you can redistribute it and/or modify it
@@ -181,17 +181,9 @@ class JvmtiTagHashmap : public CHeapObj<mtInternal> {
 
   // hash a given key (oop) with the specified size
   static unsigned int hash(oop key, int size) {
-    ZGC_ONLY(assert(ZAddressMetadataShift >= sizeof(unsigned int) * BitsPerByte, "cast removes the metadata bits");)
+    const oop obj = Access<>::resolve(key);
-
+    const unsigned int hash = Universe::heap()->hash_oop(obj);
-    // shift right to get better distribution (as these bits will be zero
+    return hash % size;
-    // with aligned addresses)
-    key = Access<>::resolve(key);
-    unsigned int addr = (unsigned int)(cast_from_oop<intptr_t>(key));
-#ifdef _LP64
-    return (addr >> 3) % size;
-#else
-    return (addr >> 2) % size;
-#endif
   }
 
   // hash a given key (oop)