1 /*
   2  * Copyright (c) 1997, 2018, Oracle and/or its affiliates. All rights reserved.
   3  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
   4  *
   5  * This code is free software; you can redistribute it and/or modify it
   6  * under the terms of the GNU General Public License version 2 only, as
   7  * published by the Free Software Foundation.
   8  *
   9  * This code is distributed in the hope that it will be useful, but WITHOUT
  10  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
  11  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
  12  * version 2 for more details (a copy is included in the LICENSE file that
  13  * accompanied this code).
  14  *
  15  * You should have received a copy of the GNU General Public License version
  16  * 2 along with this work; if not, write to the Free Software Foundation,
  17  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
  18  *
  19  * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
  20  * or visit www.oracle.com if you need additional information or have any
  21  * questions.
  22  *
  23  */
  24 
  25 #ifndef SHARE_VM_MEMORY_ALLOCATION_HPP
  26 #define SHARE_VM_MEMORY_ALLOCATION_HPP
  27 
  28 #include "runtime/globals.hpp"
  29 #include "utilities/globalDefinitions.hpp"
  30 #include "utilities/macros.hpp"
  31 
  32 #include <new>
  33 
  34 class AllocFailStrategy {
  35 public:
  36   enum AllocFailEnum { EXIT_OOM, RETURN_NULL };
  37 };
  38 typedef AllocFailStrategy::AllocFailEnum AllocFailType;
  39 
  40 // The virtual machine must never call one of the implicitly declared
  41 // global allocation or deletion functions.  (Such calls may result in
  42 // link-time or run-time errors.)  For convenience and documentation of
  43 // intended use, classes in the virtual machine may be derived from one
  44 // of the following allocation classes, some of which define allocation
  45 // and deletion functions.
  46 // Note: std::malloc and std::free should never called directly.
  47 
  48 //
  49 // For objects allocated in the resource area (see resourceArea.hpp).
  50 // - ResourceObj
  51 //
  52 // For objects allocated in the C-heap (managed by: free & malloc and tracked with NMT)
  53 // - CHeapObj
  54 //
  55 // For objects allocated on the stack.
  56 // - StackObj
  57 //
  58 // For classes used as name spaces.
  59 // - AllStatic
  60 //
  61 // For classes in Metaspace (class data)
  62 // - MetaspaceObj
  63 //
  64 // The printable subclasses are used for debugging and define virtual
  65 // member functions for printing. Classes that avoid allocating the
  66 // vtbl entries in the objects should therefore not be the printable
  67 // subclasses.
  68 //
  69 // The following macros and function should be used to allocate memory
  70 // directly in the resource area or in the C-heap, The _OBJ variants
  71 // of the NEW/FREE_C_HEAP macros are used for alloc/dealloc simple
  72 // objects which are not inherited from CHeapObj, note constructor and
  73 // destructor are not called. The preferable way to allocate objects
  74 // is using the new operator.
  75 //
  76 // WARNING: The array variant must only be used for a homogenous array
  77 // where all objects are of the exact type specified. If subtypes are
  78 // stored in the array then must pay attention to calling destructors
  79 // at needed.
  80 //
  81 //   NEW_RESOURCE_ARRAY(type, size)
  82 //   NEW_RESOURCE_OBJ(type)
  83 //   NEW_C_HEAP_ARRAY(type, size)
  84 //   NEW_C_HEAP_OBJ(type, memflags)
  85 //   FREE_C_HEAP_ARRAY(type, old)
  86 //   FREE_C_HEAP_OBJ(objname, type, memflags)
  87 //   char* AllocateHeap(size_t size, const char* name);
  88 //   void  FreeHeap(void* p);
  89 //
  90 
  91 // In non product mode we introduce a super class for all allocation classes
  92 // that supports printing.
  93 // We avoid the superclass in product mode to save space.
  94 
  95 #ifdef PRODUCT
  96 #define ALLOCATION_SUPER_CLASS_SPEC
  97 #else
  98 #define ALLOCATION_SUPER_CLASS_SPEC : public AllocatedObj
  99 class AllocatedObj {
 100  public:
 101   // Printing support
 102   void print() const;
 103   void print_value() const;
 104 
 105   virtual void print_on(outputStream* st) const;
 106   virtual void print_value_on(outputStream* st) const;
 107 };
 108 #endif
 109 
 110 #define MEMORY_TYPES_DO(f) \
 111   /* Memory type by sub systems. It occupies lower byte. */  \
 112   f(mtJavaHeap,      "Java Heap")   /* Java heap                                 */ \
 113   f(mtClass,         "Class")       /* Java classes                              */ \
 114   f(mtThread,        "Thread")      /* thread objects                            */ \
 115   f(mtThreadStack,   "Thread Stack")                                                \
 116   f(mtCode,          "Code")        /* generated code                            */ \
 117   f(mtGC,            "GC")                                                          \
 118   f(mtCompiler,      "Compiler")                                                    \
 119   f(mtInternal,      "Internal")    /* memory used by VM, but does not belong to */ \
 120                                     /* any of above categories, and not used by  */ \
 121                                     /* NMT                                       */ \
 122   f(mtOther,         "Other")       /* memory not used by VM                     */ \
 123   f(mtSymbol,        "Symbol")                                                      \
 124   f(mtNMT,           "Native Memory Tracking")  /* memory used by NMT            */ \
 125   f(mtClassShared,   "Shared class space")      /* class data sharing            */ \
 126   f(mtChunk,         "Arena Chunk") /* chunk that holds content of arenas        */ \
 127   f(mtTest,          "Test")        /* Test type for verifying NMT               */ \
 128   f(mtTracing,       "Tracing")                                                     \
 129   f(mtLogging,       "Logging")                                                     \
 130   f(mtArguments,     "Arguments")                                                   \
 131   f(mtModule,        "Module")                                                      \
 132   f(mtSafepoint,     "Safepoint")                                                   \
 133   f(mtNone,          "Unknown")                                                     \
 134   //end
 135 
 136 #define MEMORY_TYPE_DECLARE_ENUM(type, human_readable) \
 137   type,
 138 
 139 /*
 140  * Memory types
 141  */
 142 enum MemoryType {
 143   MEMORY_TYPES_DO(MEMORY_TYPE_DECLARE_ENUM)
 144   mt_number_of_types   // number of memory types (mtDontTrack
 145                        // is not included as validate type)
 146 };
 147 
 148 typedef MemoryType MEMFLAGS;
 149 
 150 
 151 #if INCLUDE_NMT
 152 
 153 extern bool NMT_track_callsite;
 154 
 155 #else
 156 
 157 const bool NMT_track_callsite = false;
 158 
 159 #endif // INCLUDE_NMT
 160 
 161 class NativeCallStack;
 162 
 163 
 164 char* AllocateHeap(size_t size,
 165                    MEMFLAGS flags,
 166                    const NativeCallStack& stack,
 167                    AllocFailType alloc_failmode = AllocFailStrategy::EXIT_OOM);
 168 char* AllocateHeap(size_t size,
 169                    MEMFLAGS flags,
 170                    AllocFailType alloc_failmode = AllocFailStrategy::EXIT_OOM);
 171 
 172 char* ReallocateHeap(char *old,
 173                      size_t size,
 174                      MEMFLAGS flag,
 175                      AllocFailType alloc_failmode = AllocFailStrategy::EXIT_OOM);
 176 
 177 void FreeHeap(void* p);
 178 
 179 template <MEMFLAGS F> class CHeapObj ALLOCATION_SUPER_CLASS_SPEC {
 180  public:
 181   ALWAYSINLINE void* operator new(size_t size) throw() {
 182     return (void*)AllocateHeap(size, F);
 183   }
 184 
 185   ALWAYSINLINE void* operator new(size_t size,
 186                                   const NativeCallStack& stack) throw() {
 187     return (void*)AllocateHeap(size, F, stack);
 188   }
 189 
 190   ALWAYSINLINE void* operator new(size_t size, const std::nothrow_t&,
 191                                   const NativeCallStack& stack) throw() {
 192     return (void*)AllocateHeap(size, F, stack, AllocFailStrategy::RETURN_NULL);
 193   }
 194 
 195   ALWAYSINLINE void* operator new(size_t size, const std::nothrow_t&) throw() {
 196     return (void*)AllocateHeap(size, F, AllocFailStrategy::RETURN_NULL);
 197   }
 198 
 199   ALWAYSINLINE void* operator new[](size_t size) throw() {
 200     return (void*)AllocateHeap(size, F);
 201   }
 202 
 203   ALWAYSINLINE void* operator new[](size_t size,
 204                                   const NativeCallStack& stack) throw() {
 205     return (void*)AllocateHeap(size, F, stack);
 206   }
 207 
 208   ALWAYSINLINE void* operator new[](size_t size, const std::nothrow_t&,
 209                                     const NativeCallStack& stack) throw() {
 210     return (void*)AllocateHeap(size, F, stack, AllocFailStrategy::RETURN_NULL);
 211   }
 212 
 213   ALWAYSINLINE void* operator new[](size_t size, const std::nothrow_t&) throw() {
 214     return (void*)AllocateHeap(size, F, AllocFailStrategy::RETURN_NULL);
 215   }
 216 
 217   void  operator delete(void* p)     { FreeHeap(p); }
 218   void  operator delete [] (void* p) { FreeHeap(p); }
 219 };
 220 
 221 // Base class for objects allocated on the stack only.
 222 // Calling new or delete will result in fatal error.
 223 
 224 class StackObj ALLOCATION_SUPER_CLASS_SPEC {
 225  private:
 226   void* operator new(size_t size) throw();
 227   void* operator new [](size_t size) throw();
 228 #ifdef __IBMCPP__
 229  public:
 230 #endif
 231   void  operator delete(void* p);
 232   void  operator delete [](void* p);
 233 };
 234 
 235 // Base class for objects stored in Metaspace.
 236 // Calling delete will result in fatal error.
 237 //
 238 // Do not inherit from something with a vptr because this class does
 239 // not introduce one.  This class is used to allocate both shared read-only
 240 // and shared read-write classes.
 241 //
 242 
 243 class ClassLoaderData;
 244 class MetaspaceClosure;
 245 
 246 class MetaspaceObj {
 247   friend class VMStructs;
 248   // When CDS is enabled, all shared metaspace objects are mapped
 249   // into a single contiguous memory block, so we can use these
 250   // two pointers to quickly determine if something is in the
 251   // shared metaspace.
 252   //
 253   // When CDS is not enabled, both pointers are set to NULL.
 254   static void* _shared_metaspace_base; // (inclusive) low address
 255   static void* _shared_metaspace_top;  // (exclusive) high address
 256 
 257  public:
 258   bool is_metaspace_object() const;
 259   bool is_shared() const {
 260     // If no shared metaspace regions are mapped, _shared_metaspace_{base,top} will
 261     // both be NULL and all values of p will be rejected quickly.
 262     return (((void*)this) < _shared_metaspace_top && ((void*)this) >= _shared_metaspace_base);
 263   }
 264   void print_address_on(outputStream* st) const;  // nonvirtual address printing
 265 
 266   static void set_shared_metaspace_range(void* base, void* top) {
 267     _shared_metaspace_base = base;
 268     _shared_metaspace_top = top;
 269   }
 270   static void* shared_metaspace_base() { return _shared_metaspace_base; }
 271   static void* shared_metaspace_top()  { return _shared_metaspace_top;  }
 272 
 273 #define METASPACE_OBJ_TYPES_DO(f) \
 274   f(Class) \
 275   f(Symbol) \
 276   f(TypeArrayU1) \
 277   f(TypeArrayU2) \
 278   f(TypeArrayU4) \
 279   f(TypeArrayU8) \
 280   f(TypeArrayOther) \
 281   f(Method) \
 282   f(ConstMethod) \
 283   f(MethodData) \
 284   f(ConstantPool) \
 285   f(ConstantPoolCache) \
 286   f(Annotations) \
 287   f(MethodCounters)
 288 
 289 #define METASPACE_OBJ_TYPE_DECLARE(name) name ## Type,
 290 #define METASPACE_OBJ_TYPE_NAME_CASE(name) case name ## Type: return #name;
 291 
 292   enum Type {
 293     // Types are MetaspaceObj::ClassType, MetaspaceObj::SymbolType, etc
 294     METASPACE_OBJ_TYPES_DO(METASPACE_OBJ_TYPE_DECLARE)
 295     _number_of_types
 296   };
 297 
 298   static const char * type_name(Type type) {
 299     switch(type) {
 300     METASPACE_OBJ_TYPES_DO(METASPACE_OBJ_TYPE_NAME_CASE)
 301     default:
 302       ShouldNotReachHere();
 303       return NULL;
 304     }
 305   }
 306 
 307   static MetaspaceObj::Type array_type(size_t elem_size) {
 308     switch (elem_size) {
 309     case 1: return TypeArrayU1Type;
 310     case 2: return TypeArrayU2Type;
 311     case 4: return TypeArrayU4Type;
 312     case 8: return TypeArrayU8Type;
 313     default:
 314       return TypeArrayOtherType;
 315     }
 316   }
 317 
 318   void* operator new(size_t size, ClassLoaderData* loader_data,
 319                      size_t word_size,
 320                      Type type, Thread* thread) throw();
 321                      // can't use TRAPS from this header file.
 322   void operator delete(void* p) { ShouldNotCallThis(); }
 323 
 324   // Declare a *static* method with the same signature in any subclass of MetaspaceObj
 325   // that should be read-only by default. See symbol.hpp for an example. This function
 326   // is used by the templates in metaspaceClosure.hpp
 327   static bool is_read_only_by_default() { return false; }
 328 };
 329 
 330 // Base class for classes that constitute name spaces.
 331 
 332 class Arena;
 333 
 334 class AllStatic {
 335  public:
 336   AllStatic()  { ShouldNotCallThis(); }
 337   ~AllStatic() { ShouldNotCallThis(); }
 338 };
 339 
 340 
 341 extern char* resource_allocate_bytes(size_t size,
 342     AllocFailType alloc_failmode = AllocFailStrategy::EXIT_OOM);
 343 extern char* resource_allocate_bytes(Thread* thread, size_t size,
 344     AllocFailType alloc_failmode = AllocFailStrategy::EXIT_OOM);
 345 extern char* resource_reallocate_bytes( char *old, size_t old_size, size_t new_size,
 346     AllocFailType alloc_failmode = AllocFailStrategy::EXIT_OOM);
 347 extern void resource_free_bytes( char *old, size_t size );
 348 
 349 //----------------------------------------------------------------------
 350 // Base class for objects allocated in the resource area per default.
 351 // Optionally, objects may be allocated on the C heap with
 352 // new(ResourceObj::C_HEAP) Foo(...) or in an Arena with new (&arena)
 353 // ResourceObj's can be allocated within other objects, but don't use
 354 // new or delete (allocation_type is unknown).  If new is used to allocate,
 355 // use delete to deallocate.
 356 class ResourceObj ALLOCATION_SUPER_CLASS_SPEC {
 357  public:
 358   enum allocation_type { STACK_OR_EMBEDDED = 0, RESOURCE_AREA, C_HEAP, ARENA, allocation_mask = 0x3 };
 359   static void set_allocation_type(address res, allocation_type type) NOT_DEBUG_RETURN;
 360 #ifdef ASSERT
 361  private:
 362   // When this object is allocated on stack the new() operator is not
 363   // called but garbage on stack may look like a valid allocation_type.
 364   // Store negated 'this' pointer when new() is called to distinguish cases.
 365   // Use second array's element for verification value to distinguish garbage.
 366   uintptr_t _allocation_t[2];
 367   bool is_type_set() const;
 368  public:
 369   allocation_type get_allocation_type() const;
 370   bool allocated_on_stack()    const { return get_allocation_type() == STACK_OR_EMBEDDED; }
 371   bool allocated_on_res_area() const { return get_allocation_type() == RESOURCE_AREA; }
 372   bool allocated_on_C_heap()   const { return get_allocation_type() == C_HEAP; }
 373   bool allocated_on_arena()    const { return get_allocation_type() == ARENA; }
 374   ResourceObj(); // default constructor
 375   ResourceObj(const ResourceObj& r); // default copy constructor
 376   ResourceObj& operator=(const ResourceObj& r); // default copy assignment
 377   ~ResourceObj();
 378 #endif // ASSERT
 379 
 380  public:
 381   void* operator new(size_t size, allocation_type type, MEMFLAGS flags) throw();
 382   void* operator new [](size_t size, allocation_type type, MEMFLAGS flags) throw();
 383   void* operator new(size_t size, const std::nothrow_t&  nothrow_constant,
 384       allocation_type type, MEMFLAGS flags) throw();
 385   void* operator new [](size_t size, const std::nothrow_t&  nothrow_constant,
 386       allocation_type type, MEMFLAGS flags) throw();
 387 
 388   void* operator new(size_t size, Arena *arena) throw();
 389 
 390   void* operator new [](size_t size, Arena *arena) throw();
 391 
 392   void* operator new(size_t size) throw() {
 393       address res = (address)resource_allocate_bytes(size);
 394       DEBUG_ONLY(set_allocation_type(res, RESOURCE_AREA);)
 395       return res;
 396   }
 397 
 398   void* operator new(size_t size, const std::nothrow_t& nothrow_constant) throw() {
 399       address res = (address)resource_allocate_bytes(size, AllocFailStrategy::RETURN_NULL);
 400       DEBUG_ONLY(if (res != NULL) set_allocation_type(res, RESOURCE_AREA);)
 401       return res;
 402   }
 403 
 404   void* operator new [](size_t size) throw() {
 405       address res = (address)resource_allocate_bytes(size);
 406       DEBUG_ONLY(set_allocation_type(res, RESOURCE_AREA);)
 407       return res;
 408   }
 409 
 410   void* operator new [](size_t size, const std::nothrow_t& nothrow_constant) throw() {
 411       address res = (address)resource_allocate_bytes(size, AllocFailStrategy::RETURN_NULL);
 412       DEBUG_ONLY(if (res != NULL) set_allocation_type(res, RESOURCE_AREA);)
 413       return res;
 414   }
 415 
 416   void  operator delete(void* p);
 417   void  operator delete [](void* p);
 418 };
 419 
 420 // One of the following macros must be used when allocating an array
 421 // or object to determine whether it should reside in the C heap on in
 422 // the resource area.
 423 
 424 #define NEW_RESOURCE_ARRAY(type, size)\
 425   (type*) resource_allocate_bytes((size) * sizeof(type))
 426 
 427 #define NEW_RESOURCE_ARRAY_RETURN_NULL(type, size)\
 428   (type*) resource_allocate_bytes((size) * sizeof(type), AllocFailStrategy::RETURN_NULL)
 429 
 430 #define NEW_RESOURCE_ARRAY_IN_THREAD(thread, type, size)\
 431   (type*) resource_allocate_bytes(thread, (size) * sizeof(type))
 432 
 433 #define NEW_RESOURCE_ARRAY_IN_THREAD_RETURN_NULL(thread, type, size)\
 434   (type*) resource_allocate_bytes(thread, (size) * sizeof(type), AllocFailStrategy::RETURN_NULL)
 435 
 436 #define REALLOC_RESOURCE_ARRAY(type, old, old_size, new_size)\
 437   (type*) resource_reallocate_bytes((char*)(old), (old_size) * sizeof(type), (new_size) * sizeof(type))
 438 
 439 #define REALLOC_RESOURCE_ARRAY_RETURN_NULL(type, old, old_size, new_size)\
 440   (type*) resource_reallocate_bytes((char*)(old), (old_size) * sizeof(type),\
 441                                     (new_size) * sizeof(type), AllocFailStrategy::RETURN_NULL)
 442 
 443 #define FREE_RESOURCE_ARRAY(type, old, size)\
 444   resource_free_bytes((char*)(old), (size) * sizeof(type))
 445 
 446 #define FREE_FAST(old)\
 447     /* nop */
 448 
 449 #define NEW_RESOURCE_OBJ(type)\
 450   NEW_RESOURCE_ARRAY(type, 1)
 451 
 452 #define NEW_RESOURCE_OBJ_RETURN_NULL(type)\
 453   NEW_RESOURCE_ARRAY_RETURN_NULL(type, 1)
 454 
 455 #define NEW_C_HEAP_ARRAY3(type, size, memflags, pc, allocfail)\
 456   (type*) AllocateHeap((size) * sizeof(type), memflags, pc, allocfail)
 457 
 458 #define NEW_C_HEAP_ARRAY2(type, size, memflags, pc)\
 459   (type*) (AllocateHeap((size) * sizeof(type), memflags, pc))
 460 
 461 #define NEW_C_HEAP_ARRAY(type, size, memflags)\
 462   (type*) (AllocateHeap((size) * sizeof(type), memflags))
 463 
 464 #define NEW_C_HEAP_ARRAY2_RETURN_NULL(type, size, memflags, pc)\
 465   NEW_C_HEAP_ARRAY3(type, (size), memflags, pc, AllocFailStrategy::RETURN_NULL)
 466 
 467 #define NEW_C_HEAP_ARRAY_RETURN_NULL(type, size, memflags)\
 468   NEW_C_HEAP_ARRAY3(type, (size), memflags, CURRENT_PC, AllocFailStrategy::RETURN_NULL)
 469 
 470 #define REALLOC_C_HEAP_ARRAY(type, old, size, memflags)\
 471   (type*) (ReallocateHeap((char*)(old), (size) * sizeof(type), memflags))
 472 
 473 #define REALLOC_C_HEAP_ARRAY_RETURN_NULL(type, old, size, memflags)\
 474   (type*) (ReallocateHeap((char*)(old), (size) * sizeof(type), memflags, AllocFailStrategy::RETURN_NULL))
 475 
 476 #define FREE_C_HEAP_ARRAY(type, old) \
 477   FreeHeap((char*)(old))
 478 
 479 // allocate type in heap without calling ctor
 480 #define NEW_C_HEAP_OBJ(type, memflags)\
 481   NEW_C_HEAP_ARRAY(type, 1, memflags)
 482 
 483 #define NEW_C_HEAP_OBJ_RETURN_NULL(type, memflags)\
 484   NEW_C_HEAP_ARRAY_RETURN_NULL(type, 1, memflags)
 485 
 486 // deallocate obj of type in heap without calling dtor
 487 #define FREE_C_HEAP_OBJ(objname)\
 488   FreeHeap((char*)objname);
 489 
 490 // for statistics
 491 #ifndef PRODUCT
 492 class AllocStats : StackObj {
 493   julong start_mallocs, start_frees;
 494   julong start_malloc_bytes, start_mfree_bytes, start_res_bytes;
 495  public:
 496   AllocStats();
 497 
 498   julong num_mallocs();    // since creation of receiver
 499   julong alloc_bytes();
 500   julong num_frees();
 501   julong free_bytes();
 502   julong resource_bytes();
 503   void   print();
 504 };
 505 #endif
 506 
 507 
 508 //------------------------------ReallocMark---------------------------------
 509 // Code which uses REALLOC_RESOURCE_ARRAY should check an associated
 510 // ReallocMark, which is declared in the same scope as the reallocated
 511 // pointer.  Any operation that could __potentially__ cause a reallocation
 512 // should check the ReallocMark.
 513 class ReallocMark: public StackObj {
 514 protected:
 515   NOT_PRODUCT(int _nesting;)
 516 
 517 public:
 518   ReallocMark()   PRODUCT_RETURN;
 519   void check()    PRODUCT_RETURN;
 520 };
 521 
 522 // Helper class to allocate arrays that may become large.
 523 // Uses the OS malloc for allocations smaller than ArrayAllocatorMallocLimit
 524 // and uses mapped memory for larger allocations.
 525 // Most OS mallocs do something similar but Solaris malloc does not revert
 526 // to mapped memory for large allocations. By default ArrayAllocatorMallocLimit
 527 // is set so that we always use malloc except for Solaris where we set the
 528 // limit to get mapped memory.
 529 template <class E>
 530 class ArrayAllocator : public AllStatic {
 531  private:
 532   static bool should_use_malloc(size_t length);
 533 
 534   static E* allocate_malloc(size_t length, MEMFLAGS flags);
 535   static E* allocate_mmap(size_t length, MEMFLAGS flags);
 536 
 537   static void free_malloc(E* addr, size_t length);
 538   static void free_mmap(E* addr, size_t length);
 539 
 540  public:
 541   static E* allocate(size_t length, MEMFLAGS flags);
 542   static E* reallocate(E* old_addr, size_t old_length, size_t new_length, MEMFLAGS flags);
 543   static void free(E* addr, size_t length);
 544 };
 545 
 546 // Uses mmaped memory for all allocations. All allocations are initially
 547 // zero-filled. No pre-touching.
 548 template <class E>
 549 class MmapArrayAllocator : public AllStatic {
 550  private:
 551   static size_t size_for(size_t length);
 552 
 553  public:
 554   static E* allocate_or_null(size_t length, MEMFLAGS flags);
 555   static E* allocate(size_t length, MEMFLAGS flags);
 556   static void free(E* addr, size_t length);
 557 };
 558 
 559 // Uses malloc:ed memory for all allocations.
 560 template <class E>
 561 class MallocArrayAllocator : public AllStatic {
 562  public:
 563   static size_t size_for(size_t length);
 564 
 565   static E* allocate(size_t length, MEMFLAGS flags);
 566   static void free(E* addr);
 567 };
 568 
 569 #endif // SHARE_VM_MEMORY_ALLOCATION_HPP