1 /*
   2  * Copyright (c) 1997, 2019, 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_MEMORY_ALLOCATION_HPP
  26 #define SHARE_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 Thread;
  35 
  36 class AllocFailStrategy {
  37 public:
  38   enum AllocFailEnum { EXIT_OOM, RETURN_NULL };
  39 };
  40 typedef AllocFailStrategy::AllocFailEnum AllocFailType;
  41 
  42 // The virtual machine must never call one of the implicitly declared
  43 // global allocation or deletion functions.  (Such calls may result in
  44 // link-time or run-time errors.)  For convenience and documentation of
  45 // intended use, classes in the virtual machine may be derived from one
  46 // of the following allocation classes, some of which define allocation
  47 // and deletion functions.
  48 // Note: std::malloc and std::free should never called directly.
  49 
  50 //
  51 // For objects allocated in the resource area (see resourceArea.hpp).
  52 // - ResourceObj
  53 //
  54 // For objects allocated in the C-heap (managed by: free & malloc and tracked with NMT)
  55 // - CHeapObj
  56 //
  57 // For objects allocated on the stack.
  58 // - StackObj
  59 //
  60 // For classes used as name spaces.
  61 // - AllStatic
  62 //
  63 // For classes in Metaspace (class data)
  64 // - MetaspaceObj
  65 //
  66 // The printable subclasses are used for debugging and define virtual
  67 // member functions for printing. Classes that avoid allocating the
  68 // vtbl entries in the objects should therefore not be the printable
  69 // subclasses.
  70 //
  71 // The following macros and function should be used to allocate memory
  72 // directly in the resource area or in the C-heap, The _OBJ variants
  73 // of the NEW/FREE_C_HEAP macros are used for alloc/dealloc simple
  74 // objects which are not inherited from CHeapObj, note constructor and
  75 // destructor are not called. The preferable way to allocate objects
  76 // is using the new operator.
  77 //
  78 // WARNING: The array variant must only be used for a homogenous array
  79 // where all objects are of the exact type specified. If subtypes are
  80 // stored in the array then must pay attention to calling destructors
  81 // at needed.
  82 //
  83 //   NEW_RESOURCE_ARRAY(type, size)
  84 //   NEW_RESOURCE_OBJ(type)
  85 //   NEW_C_HEAP_ARRAY(type, size)
  86 //   NEW_C_HEAP_OBJ(type, memflags)
  87 //   FREE_C_HEAP_ARRAY(type, old)
  88 //   FREE_C_HEAP_OBJ(objname, type, memflags)
  89 //   char* AllocateHeap(size_t size, const char* name);
  90 //   void  FreeHeap(void* p);
  91 //
  92 
  93 // In non product mode we introduce a super class for all allocation classes
  94 // that supports printing.
  95 // We avoid the superclass in product mode to save space.
  96 
  97 #ifdef PRODUCT
  98 #define ALLOCATION_SUPER_CLASS_SPEC
  99 #else
 100 #define ALLOCATION_SUPER_CLASS_SPEC : public AllocatedObj
 101 class AllocatedObj {
 102  public:
 103   // Printing support
 104   void print() const;
 105   void print_value() const;
 106 
 107   virtual void print_on(outputStream* st) const;
 108   virtual void print_value_on(outputStream* st) const;
 109 };
 110 #endif
 111 
 112 #define MEMORY_TYPES_DO(f) \
 113   /* Memory type by sub systems. It occupies lower byte. */  \
 114   f(mtJavaHeap,      "Java Heap")   /* Java heap                                 */ \
 115   f(mtClass,         "Class")       /* Java classes                              */ \
 116   f(mtThread,        "Thread")      /* thread objects                            */ \
 117   f(mtThreadStack,   "Thread Stack")                                                \
 118   f(mtCode,          "Code")        /* generated code                            */ \
 119   f(mtGC,            "GC")                                                          \
 120   f(mtCompiler,      "Compiler")                                                    \
 121   f(mtJVMCI,         "JVMCI")                                                       \
 122   f(mtInternal,      "Internal")    /* memory used by VM, but does not belong to */ \
 123                                     /* any of above categories, and not used by  */ \
 124                                     /* NMT                                       */ \
 125   f(mtOther,         "Other")       /* memory not used by VM                     */ \
 126   f(mtSymbol,        "Symbol")                                                      \
 127   f(mtNMT,           "Native Memory Tracking")  /* memory used by NMT            */ \
 128   f(mtClassShared,   "Shared class space")      /* class data sharing            */ \
 129   f(mtChunk,         "Arena Chunk") /* chunk that holds content of arenas        */ \
 130   f(mtTest,          "Test")        /* Test type for verifying NMT               */ \
 131   f(mtTracing,       "Tracing")                                                     \
 132   f(mtLogging,       "Logging")                                                     \
 133   f(mtStatistics,    "Statistics")                                                  \
 134   f(mtArguments,     "Arguments")                                                   \
 135   f(mtModule,        "Module")                                                      \
 136   f(mtSafepoint,     "Safepoint")                                                   \
 137   f(mtSynchronizer,  "Synchronization")                                             \
 138   f(mtNone,          "Unknown")                                                     \
 139   //end
 140 
 141 #define MEMORY_TYPE_DECLARE_ENUM(type, human_readable) \
 142   type,
 143 
 144 /*
 145  * Memory types
 146  */
 147 enum MemoryType {
 148   MEMORY_TYPES_DO(MEMORY_TYPE_DECLARE_ENUM)
 149   mtValueTypes,        // memory for buffered value types
 150   mt_number_of_types   // number of memory types (mtDontTrack
 151                        // is not included as validate type)
 152 };
 153 
 154 typedef MemoryType MEMFLAGS;
 155 
 156 
 157 #if INCLUDE_NMT
 158 
 159 extern bool NMT_track_callsite;
 160 
 161 #else
 162 
 163 const bool NMT_track_callsite = false;
 164 
 165 #endif // INCLUDE_NMT
 166 
 167 class NativeCallStack;
 168 
 169 
 170 char* AllocateHeap(size_t size,
 171                    MEMFLAGS flags,
 172                    const NativeCallStack& stack,
 173                    AllocFailType alloc_failmode = AllocFailStrategy::EXIT_OOM);
 174 char* AllocateHeap(size_t size,
 175                    MEMFLAGS flags,
 176                    AllocFailType alloc_failmode = AllocFailStrategy::EXIT_OOM);
 177 
 178 char* ReallocateHeap(char *old,
 179                      size_t size,
 180                      MEMFLAGS flag,
 181                      AllocFailType alloc_failmode = AllocFailStrategy::EXIT_OOM);
 182 
 183 void FreeHeap(void* p);
 184 
 185 template <MEMFLAGS F> class CHeapObj ALLOCATION_SUPER_CLASS_SPEC {
 186  public:
 187   ALWAYSINLINE void* operator new(size_t size) throw() {
 188     return (void*)AllocateHeap(size, F);
 189   }
 190 
 191   ALWAYSINLINE void* operator new(size_t size,
 192                                   const NativeCallStack& stack) throw() {
 193     return (void*)AllocateHeap(size, F, stack);
 194   }
 195 
 196   ALWAYSINLINE void* operator new(size_t size, const std::nothrow_t&,
 197                                   const NativeCallStack& stack) throw() {
 198     return (void*)AllocateHeap(size, F, stack, AllocFailStrategy::RETURN_NULL);
 199   }
 200 
 201   ALWAYSINLINE void* operator new(size_t size, const std::nothrow_t&) throw() {
 202     return (void*)AllocateHeap(size, F, AllocFailStrategy::RETURN_NULL);
 203   }
 204 
 205   ALWAYSINLINE void* operator new[](size_t size) throw() {
 206     return (void*)AllocateHeap(size, F);
 207   }
 208 
 209   ALWAYSINLINE void* operator new[](size_t size,
 210                                   const NativeCallStack& stack) throw() {
 211     return (void*)AllocateHeap(size, F, stack);
 212   }
 213 
 214   ALWAYSINLINE void* operator new[](size_t size, const std::nothrow_t&,
 215                                     const NativeCallStack& stack) throw() {
 216     return (void*)AllocateHeap(size, F, stack, AllocFailStrategy::RETURN_NULL);
 217   }
 218 
 219   ALWAYSINLINE void* operator new[](size_t size, const std::nothrow_t&) throw() {
 220     return (void*)AllocateHeap(size, F, AllocFailStrategy::RETURN_NULL);
 221   }
 222 
 223   void  operator delete(void* p)     { FreeHeap(p); }
 224   void  operator delete [] (void* p) { FreeHeap(p); }
 225 };
 226 
 227 // Base class for objects allocated on the stack only.
 228 // Calling new or delete will result in fatal error.
 229 
 230 class StackObj ALLOCATION_SUPER_CLASS_SPEC {
 231  private:
 232   void* operator new(size_t size) throw();
 233   void* operator new [](size_t size) throw();
 234 #ifdef __IBMCPP__
 235  public:
 236 #endif
 237   void  operator delete(void* p);
 238   void  operator delete [](void* p);
 239 };
 240 
 241 // Base class for objects stored in Metaspace.
 242 // Calling delete will result in fatal error.
 243 //
 244 // Do not inherit from something with a vptr because this class does
 245 // not introduce one.  This class is used to allocate both shared read-only
 246 // and shared read-write classes.
 247 //
 248 
 249 class ClassLoaderData;
 250 class MetaspaceClosure;
 251 
 252 class MetaspaceObj {
 253   friend class VMStructs;
 254   // When CDS is enabled, all shared metaspace objects are mapped
 255   // into a single contiguous memory block, so we can use these
 256   // two pointers to quickly determine if something is in the
 257   // shared metaspace.
 258   // When CDS is not enabled, both pointers are set to NULL.
 259   static void* _shared_metaspace_base;  // (inclusive) low address
 260   static void* _shared_metaspace_top;   // (exclusive) high address
 261 
 262  public:
 263 
 264   // Returns true if the pointer points to a valid MetaspaceObj. A valid
 265   // MetaspaceObj is MetaWord-aligned and contained within either
 266   // non-shared or shared metaspace.
 267   static bool is_valid(const MetaspaceObj* p);
 268 
 269   static bool is_shared(const MetaspaceObj* p) {
 270     // If no shared metaspace regions are mapped, _shared_metaspace_{base,top} will
 271     // both be NULL and all values of p will be rejected quickly.
 272     return (((void*)p) < _shared_metaspace_top &&
 273             ((void*)p) >= _shared_metaspace_base);
 274   }
 275   bool is_shared() const { return MetaspaceObj::is_shared(this); }
 276 
 277   void print_address_on(outputStream* st) const;  // nonvirtual address printing
 278 
 279   static void set_shared_metaspace_range(void* base, void* top) {
 280     _shared_metaspace_base = base;
 281     _shared_metaspace_top = top;
 282   }
 283 
 284   static void expand_shared_metaspace_range(void* top) {
 285     assert(top >= _shared_metaspace_top, "must be");
 286     _shared_metaspace_top = top;
 287   }
 288 
 289   static void* shared_metaspace_base() { return _shared_metaspace_base; }
 290   static void* shared_metaspace_top()  { return _shared_metaspace_top;  }
 291 
 292 #define METASPACE_OBJ_TYPES_DO(f) \
 293   f(Class) \
 294   f(Symbol) \
 295   f(TypeArrayU1) \
 296   f(TypeArrayU2) \
 297   f(TypeArrayU4) \
 298   f(TypeArrayU8) \
 299   f(TypeArrayOther) \
 300   f(Method) \
 301   f(ConstMethod) \
 302   f(MethodData) \
 303   f(ConstantPool) \
 304   f(ConstantPoolCache) \
 305   f(Annotations) \
 306   f(MethodCounters)
 307 
 308 #define METASPACE_OBJ_TYPE_DECLARE(name) name ## Type,
 309 #define METASPACE_OBJ_TYPE_NAME_CASE(name) case name ## Type: return #name;
 310 
 311   enum Type {
 312     // Types are MetaspaceObj::ClassType, MetaspaceObj::SymbolType, etc
 313     METASPACE_OBJ_TYPES_DO(METASPACE_OBJ_TYPE_DECLARE)
 314     _number_of_types
 315   };
 316 
 317   static const char * type_name(Type type) {
 318     switch(type) {
 319     METASPACE_OBJ_TYPES_DO(METASPACE_OBJ_TYPE_NAME_CASE)
 320     default:
 321       ShouldNotReachHere();
 322       return NULL;
 323     }
 324   }
 325 
 326   static MetaspaceObj::Type array_type(size_t elem_size) {
 327     switch (elem_size) {
 328     case 1: return TypeArrayU1Type;
 329     case 2: return TypeArrayU2Type;
 330     case 4: return TypeArrayU4Type;
 331     case 8: return TypeArrayU8Type;
 332     default:
 333       return TypeArrayOtherType;
 334     }
 335   }
 336 
 337   void* operator new(size_t size, ClassLoaderData* loader_data,
 338                      size_t word_size,
 339                      Type type, Thread* thread) throw();
 340                      // can't use TRAPS from this header file.
 341   void operator delete(void* p) { ShouldNotCallThis(); }
 342 
 343   // Declare a *static* method with the same signature in any subclass of MetaspaceObj
 344   // that should be read-only by default. See symbol.hpp for an example. This function
 345   // is used by the templates in metaspaceClosure.hpp
 346   static bool is_read_only_by_default() { return false; }
 347 };
 348 
 349 // Base class for classes that constitute name spaces.
 350 
 351 class Arena;
 352 
 353 class AllStatic {
 354  public:
 355   AllStatic()  { ShouldNotCallThis(); }
 356   ~AllStatic() { ShouldNotCallThis(); }
 357 };
 358 
 359 
 360 extern char* resource_allocate_bytes(size_t size,
 361     AllocFailType alloc_failmode = AllocFailStrategy::EXIT_OOM);
 362 extern char* resource_allocate_bytes(Thread* thread, size_t size,
 363     AllocFailType alloc_failmode = AllocFailStrategy::EXIT_OOM);
 364 extern char* resource_reallocate_bytes( char *old, size_t old_size, size_t new_size,
 365     AllocFailType alloc_failmode = AllocFailStrategy::EXIT_OOM);
 366 extern void resource_free_bytes( char *old, size_t size );
 367 
 368 //----------------------------------------------------------------------
 369 // Base class for objects allocated in the resource area per default.
 370 // Optionally, objects may be allocated on the C heap with
 371 // new(ResourceObj::C_HEAP) Foo(...) or in an Arena with new (&arena)
 372 // ResourceObj's can be allocated within other objects, but don't use
 373 // new or delete (allocation_type is unknown).  If new is used to allocate,
 374 // use delete to deallocate.
 375 class ResourceObj ALLOCATION_SUPER_CLASS_SPEC {
 376  public:
 377   enum allocation_type { STACK_OR_EMBEDDED = 0, RESOURCE_AREA, C_HEAP, ARENA, allocation_mask = 0x3 };
 378   static void set_allocation_type(address res, allocation_type type) NOT_DEBUG_RETURN;
 379 #ifdef ASSERT
 380  private:
 381   // When this object is allocated on stack the new() operator is not
 382   // called but garbage on stack may look like a valid allocation_type.
 383   // Store negated 'this' pointer when new() is called to distinguish cases.
 384   // Use second array's element for verification value to distinguish garbage.
 385   uintptr_t _allocation_t[2];
 386   bool is_type_set() const;
 387   void initialize_allocation_info();
 388  public:
 389   allocation_type get_allocation_type() const;
 390   bool allocated_on_stack()    const { return get_allocation_type() == STACK_OR_EMBEDDED; }
 391   bool allocated_on_res_area() const { return get_allocation_type() == RESOURCE_AREA; }
 392   bool allocated_on_C_heap()   const { return get_allocation_type() == C_HEAP; }
 393   bool allocated_on_arena()    const { return get_allocation_type() == ARENA; }
 394 protected:
 395   ResourceObj(); // default constructor
 396   ResourceObj(const ResourceObj& r); // default copy constructor
 397   ResourceObj& operator=(const ResourceObj& r); // default copy assignment
 398   ~ResourceObj();
 399 #endif // ASSERT
 400 
 401  public:
 402   void* operator new(size_t size, allocation_type type, MEMFLAGS flags) throw();
 403   void* operator new [](size_t size, allocation_type type, MEMFLAGS flags) throw();
 404   void* operator new(size_t size, const std::nothrow_t&  nothrow_constant,
 405       allocation_type type, MEMFLAGS flags) throw();
 406   void* operator new [](size_t size, const std::nothrow_t&  nothrow_constant,
 407       allocation_type type, MEMFLAGS flags) throw();
 408 
 409   void* operator new(size_t size, Arena *arena) throw();
 410 
 411   void* operator new [](size_t size, Arena *arena) throw();
 412 
 413   void* operator new(size_t size) throw() {
 414       address res = (address)resource_allocate_bytes(size);
 415       DEBUG_ONLY(set_allocation_type(res, RESOURCE_AREA);)
 416       return res;
 417   }
 418 
 419   void* operator new(size_t size, const std::nothrow_t& nothrow_constant) throw() {
 420       address res = (address)resource_allocate_bytes(size, AllocFailStrategy::RETURN_NULL);
 421       DEBUG_ONLY(if (res != NULL) set_allocation_type(res, RESOURCE_AREA);)
 422       return res;
 423   }
 424 
 425   void* operator new [](size_t size) throw() {
 426       address res = (address)resource_allocate_bytes(size);
 427       DEBUG_ONLY(set_allocation_type(res, RESOURCE_AREA);)
 428       return res;
 429   }
 430 
 431   void* operator new [](size_t size, const std::nothrow_t& nothrow_constant) throw() {
 432       address res = (address)resource_allocate_bytes(size, AllocFailStrategy::RETURN_NULL);
 433       DEBUG_ONLY(if (res != NULL) set_allocation_type(res, RESOURCE_AREA);)
 434       return res;
 435   }
 436 
 437   void  operator delete(void* p);
 438   void  operator delete [](void* p);
 439 };
 440 
 441 // One of the following macros must be used when allocating an array
 442 // or object to determine whether it should reside in the C heap on in
 443 // the resource area.
 444 
 445 #define NEW_RESOURCE_ARRAY(type, size)\
 446   (type*) resource_allocate_bytes((size) * sizeof(type))
 447 
 448 #define NEW_RESOURCE_ARRAY_RETURN_NULL(type, size)\
 449   (type*) resource_allocate_bytes((size) * sizeof(type), AllocFailStrategy::RETURN_NULL)
 450 
 451 #define NEW_RESOURCE_ARRAY_IN_THREAD(thread, type, size)\
 452   (type*) resource_allocate_bytes(thread, (size) * sizeof(type))
 453 
 454 #define NEW_RESOURCE_ARRAY_IN_THREAD_RETURN_NULL(thread, type, size)\
 455   (type*) resource_allocate_bytes(thread, (size) * sizeof(type), AllocFailStrategy::RETURN_NULL)
 456 
 457 #define REALLOC_RESOURCE_ARRAY(type, old, old_size, new_size)\
 458   (type*) resource_reallocate_bytes((char*)(old), (old_size) * sizeof(type), (new_size) * sizeof(type))
 459 
 460 #define REALLOC_RESOURCE_ARRAY_RETURN_NULL(type, old, old_size, new_size)\
 461   (type*) resource_reallocate_bytes((char*)(old), (old_size) * sizeof(type),\
 462                                     (new_size) * sizeof(type), AllocFailStrategy::RETURN_NULL)
 463 
 464 #define FREE_RESOURCE_ARRAY(type, old, size)\
 465   resource_free_bytes((char*)(old), (size) * sizeof(type))
 466 
 467 #define FREE_FAST(old)\
 468     /* nop */
 469 
 470 #define NEW_RESOURCE_OBJ(type)\
 471   NEW_RESOURCE_ARRAY(type, 1)
 472 
 473 #define NEW_RESOURCE_OBJ_RETURN_NULL(type)\
 474   NEW_RESOURCE_ARRAY_RETURN_NULL(type, 1)
 475 
 476 #define NEW_C_HEAP_ARRAY3(type, size, memflags, pc, allocfail)\
 477   (type*) AllocateHeap((size) * sizeof(type), memflags, pc, allocfail)
 478 
 479 #define NEW_C_HEAP_ARRAY2(type, size, memflags, pc)\
 480   (type*) (AllocateHeap((size) * sizeof(type), memflags, pc))
 481 
 482 #define NEW_C_HEAP_ARRAY(type, size, memflags)\
 483   (type*) (AllocateHeap((size) * sizeof(type), memflags))
 484 
 485 #define NEW_C_HEAP_ARRAY2_RETURN_NULL(type, size, memflags, pc)\
 486   NEW_C_HEAP_ARRAY3(type, (size), memflags, pc, AllocFailStrategy::RETURN_NULL)
 487 
 488 #define NEW_C_HEAP_ARRAY_RETURN_NULL(type, size, memflags)\
 489   NEW_C_HEAP_ARRAY3(type, (size), memflags, CURRENT_PC, AllocFailStrategy::RETURN_NULL)
 490 
 491 #define REALLOC_C_HEAP_ARRAY(type, old, size, memflags)\
 492   (type*) (ReallocateHeap((char*)(old), (size) * sizeof(type), memflags))
 493 
 494 #define REALLOC_C_HEAP_ARRAY_RETURN_NULL(type, old, size, memflags)\
 495   (type*) (ReallocateHeap((char*)(old), (size) * sizeof(type), memflags, AllocFailStrategy::RETURN_NULL))
 496 
 497 #define FREE_C_HEAP_ARRAY(type, old) \
 498   FreeHeap((char*)(old))
 499 
 500 // allocate type in heap without calling ctor
 501 #define NEW_C_HEAP_OBJ(type, memflags)\
 502   NEW_C_HEAP_ARRAY(type, 1, memflags)
 503 
 504 #define NEW_C_HEAP_OBJ_RETURN_NULL(type, memflags)\
 505   NEW_C_HEAP_ARRAY_RETURN_NULL(type, 1, memflags)
 506 
 507 // deallocate obj of type in heap without calling dtor
 508 #define FREE_C_HEAP_OBJ(objname)\
 509   FreeHeap((char*)objname);
 510 
 511 // for statistics
 512 #ifndef PRODUCT
 513 class AllocStats : StackObj {
 514   julong start_mallocs, start_frees;
 515   julong start_malloc_bytes, start_mfree_bytes, start_res_bytes;
 516  public:
 517   AllocStats();
 518 
 519   julong num_mallocs();    // since creation of receiver
 520   julong alloc_bytes();
 521   julong num_frees();
 522   julong free_bytes();
 523   julong resource_bytes();
 524   void   print();
 525 };
 526 #endif
 527 
 528 
 529 //------------------------------ReallocMark---------------------------------
 530 // Code which uses REALLOC_RESOURCE_ARRAY should check an associated
 531 // ReallocMark, which is declared in the same scope as the reallocated
 532 // pointer.  Any operation that could __potentially__ cause a reallocation
 533 // should check the ReallocMark.
 534 class ReallocMark: public StackObj {
 535 protected:
 536   NOT_PRODUCT(int _nesting;)
 537 
 538 public:
 539   ReallocMark()   PRODUCT_RETURN;
 540   void check()    PRODUCT_RETURN;
 541 };
 542 
 543 // Helper class to allocate arrays that may become large.
 544 // Uses the OS malloc for allocations smaller than ArrayAllocatorMallocLimit
 545 // and uses mapped memory for larger allocations.
 546 // Most OS mallocs do something similar but Solaris malloc does not revert
 547 // to mapped memory for large allocations. By default ArrayAllocatorMallocLimit
 548 // is set so that we always use malloc except for Solaris where we set the
 549 // limit to get mapped memory.
 550 template <class E>
 551 class ArrayAllocator : public AllStatic {
 552  private:
 553   static bool should_use_malloc(size_t length);
 554 
 555   static E* allocate_malloc(size_t length, MEMFLAGS flags);
 556   static E* allocate_mmap(size_t length, MEMFLAGS flags);
 557 
 558   static void free_malloc(E* addr, size_t length);
 559   static void free_mmap(E* addr, size_t length);
 560 
 561  public:
 562   static E* allocate(size_t length, MEMFLAGS flags);
 563   static E* reallocate(E* old_addr, size_t old_length, size_t new_length, MEMFLAGS flags);
 564   static void free(E* addr, size_t length);
 565 };
 566 
 567 // Uses mmaped memory for all allocations. All allocations are initially
 568 // zero-filled. No pre-touching.
 569 template <class E>
 570 class MmapArrayAllocator : public AllStatic {
 571  private:
 572   static size_t size_for(size_t length);
 573 
 574  public:
 575   static E* allocate_or_null(size_t length, MEMFLAGS flags);
 576   static E* allocate(size_t length, MEMFLAGS flags);
 577   static void free(E* addr, size_t length);
 578 };
 579 
 580 // Uses malloc:ed memory for all allocations.
 581 template <class E>
 582 class MallocArrayAllocator : public AllStatic {
 583  public:
 584   static size_t size_for(size_t length);
 585 
 586   static E* allocate(size_t length, MEMFLAGS flags);
 587   static void free(E* addr);
 588 };
 589 
 590 #endif // SHARE_MEMORY_ALLOCATION_HPP