1 // MT-optimized allocator -*- C++ -*-
3 // Copyright (C) 2003, 2004, 2005, 2006, 2007, 2008, 2009
4 // Free Software Foundation, Inc.
6 // This file is part of the GNU ISO C++ Library. This library is free
7 // software; you can redistribute it and/or modify it under the
8 // terms of the GNU General Public License as published by the
9 // Free Software Foundation; either version 2, or (at your option)
12 // This library is distributed in the hope that it will be useful,
13 // but WITHOUT ANY WARRANTY; without even the implied warranty of
14 // MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
15 // GNU General Public License for more details.
17 // You should have received a copy of the GNU General Public License along
18 // with this library; see the file COPYING. If not, write to the Free
19 // Software Foundation, 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301,
22 // As a special exception, you may use this file as part of a free software
23 // library without restriction. Specifically, if other files instantiate
24 // templates or use macros or inline functions from this file, or you compile
25 // this file and link it with other files to produce an executable, this
26 // file does not by itself cause the resulting executable to be covered by
27 // the GNU General Public License. This exception does not however
28 // invalidate any other reasons why the executable file might be covered by
29 // the GNU General Public License.
31 /** @file ext/mt_allocator.h
32 * This file is a GNU extension to the Standard C++ Library.
35 #ifndef _MT_ALLOCATOR_H
36 #define _MT_ALLOCATOR_H 1
40 #include <bits/functexcept.h>
41 #include <ext/atomicity.h>
42 #include <bits/move.h>
44 _GLIBCXX_BEGIN_NAMESPACE(__gnu_cxx)
49 typedef void (*__destroy_handler)(void*);
51 /// Base class for pool object.
54 // Using short int as type for the binmap implies we are never
55 // caching blocks larger than 32768 with this allocator.
56 typedef unsigned short int _Binmap_type;
58 // Variables used to configure the behavior of the allocator,
59 // assigned and explained in detail below.
62 // Compile time constants for the default _Tune values.
63 enum { _S_align = 8 };
64 enum { _S_max_bytes = 128 };
65 enum { _S_min_bin = 8 };
66 enum { _S_chunk_size = 4096 - 4 * sizeof(void*) };
67 enum { _S_max_threads = 4096 };
68 enum { _S_freelist_headroom = 10 };
71 // NB: In any case must be >= sizeof(_Block_record), that
72 // is 4 on 32 bit machines and 8 on 64 bit machines.
75 // Allocation requests (after round-up to power of 2) below
76 // this value will be handled by the allocator. A raw new/
77 // call will be used for requests larger than this value.
78 // NB: Must be much smaller than _M_chunk_size and in any
82 // Size in bytes of the smallest bin.
83 // NB: Must be a power of 2 and >= _M_align (and of course
84 // much smaller than _M_max_bytes).
87 // In order to avoid fragmenting and minimize the number of
88 // new() calls we always request new memory using this
89 // value. Based on previous discussions on the libstdc++
90 // mailing list we have chosen the value below.
91 // See http://gcc.gnu.org/ml/libstdc++/2001-07/msg00077.html
92 // NB: At least one order of magnitude > _M_max_bytes.
95 // The maximum number of supported threads. For
96 // single-threaded operation, use one. Maximum values will
97 // vary depending on details of the underlying system. (For
98 // instance, Linux 2.4.18 reports 4070 in
99 // /proc/sys/kernel/threads-max, while Linux 2.6.6 reports
101 size_t _M_max_threads;
103 // Each time a deallocation occurs in a threaded application
104 // we make sure that there are no more than
105 // _M_freelist_headroom % of used memory on the freelist. If
106 // the number of additional records is more than
107 // _M_freelist_headroom % of the freelist, we move these
108 // records back to the global pool.
109 size_t _M_freelist_headroom;
111 // Set to true forces all allocations to use new().
116 : _M_align(_S_align), _M_max_bytes(_S_max_bytes), _M_min_bin(_S_min_bin),
117 _M_chunk_size(_S_chunk_size), _M_max_threads(_S_max_threads),
118 _M_freelist_headroom(_S_freelist_headroom),
119 _M_force_new(std::getenv("GLIBCXX_FORCE_NEW") ? true : false)
123 _Tune(size_t __align, size_t __maxb, size_t __minbin, size_t __chunk,
124 size_t __maxthreads, size_t __headroom, bool __force)
125 : _M_align(__align), _M_max_bytes(__maxb), _M_min_bin(__minbin),
126 _M_chunk_size(__chunk), _M_max_threads(__maxthreads),
127 _M_freelist_headroom(__headroom), _M_force_new(__force)
131 struct _Block_address
134 _Block_address* _M_next;
138 _M_get_options() const
139 { return _M_options; }
142 _M_set_options(_Tune __t)
149 _M_check_threshold(size_t __bytes)
150 { return __bytes > _M_options._M_max_bytes || _M_options._M_force_new; }
153 _M_get_binmap(size_t __bytes)
154 { return _M_binmap[__bytes]; }
158 { return _M_options._M_align; }
162 : _M_options(_Tune()), _M_binmap(NULL), _M_init(false) { }
165 __pool_base(const _Tune& __options)
166 : _M_options(__options), _M_binmap(NULL), _M_init(false) { }
170 __pool_base(const __pool_base&);
173 operator=(const __pool_base&);
176 // Configuration options.
179 _Binmap_type* _M_binmap;
181 // Configuration of the pool object via _M_options can happen
182 // after construction but before initialization. After
183 // initialization is complete, this variable is set to true.
189 * @brief Data describing the underlying memory pool, parameterized on
192 template<bool _Thread>
195 /// Specialization for single thread.
197 class __pool<false> : public __pool_base
202 // Points to the block_record of the next free block.
203 _Block_record* _M_next;
208 // An "array" of pointers to the first free block.
209 _Block_record** _M_first;
211 // A list of the initial addresses of all allocated blocks.
212 _Block_address* _M_address;
218 if (__builtin_expect(_M_init == false, false))
223 _M_destroy() throw();
226 _M_reserve_block(size_t __bytes, const size_t __thread_id);
229 _M_reclaim_block(char* __p, size_t __bytes);
232 _M_get_thread_id() { return 0; }
235 _M_get_bin(size_t __which)
236 { return _M_bin[__which]; }
239 _M_adjust_freelist(const _Bin_record&, _Block_record*, size_t)
243 : _M_bin(NULL), _M_bin_size(1) { }
245 explicit __pool(const __pool_base::_Tune& __tune)
246 : __pool_base(__tune), _M_bin(NULL), _M_bin_size(1) { }
249 // An "array" of bin_records each of which represents a specific
250 // power of 2 size. Memory to this "array" is allocated in
254 // Actual value calculated in _M_initialize().
262 /// Specialization for thread enabled, via gthreads.h.
264 class __pool<true> : public __pool_base
267 // Each requesting thread is assigned an id ranging from 1 to
268 // _S_max_threads. Thread id 0 is used as a global memory pool.
269 // In order to get constant performance on the thread assignment
270 // routine, we keep a list of free ids. When a thread first
271 // requests memory we remove the first record in this list and
272 // stores the address in a __gthread_key. When initializing the
273 // __gthread_key we specify a destructor. When this destructor
274 // (i.e. the thread dies) is called, we return the thread id to
275 // the front of this list.
276 struct _Thread_record
278 // Points to next free thread id record. NULL if last record in list.
279 _Thread_record* _M_next;
281 // Thread id ranging from 1 to _S_max_threads.
287 // Points to the block_record of the next free block.
288 _Block_record* _M_next;
290 // The thread id of the thread which has requested this block.
296 // An "array" of pointers to the first free block for each
297 // thread id. Memory to this "array" is allocated in
298 // _S_initialize() for _S_max_threads + global pool 0.
299 _Block_record** _M_first;
301 // A list of the initial addresses of all allocated blocks.
302 _Block_address* _M_address;
304 // An "array" of counters used to keep track of the amount of
305 // blocks that are on the freelist/used for each thread id.
306 // - Note that the second part of the allocated _M_used "array"
307 // actually hosts (atomic) counters of reclaimed blocks: in
308 // _M_reserve_block and in _M_reclaim_block those numbers are
309 // subtracted from the first ones to obtain the actual size
310 // of the "working set" of the given thread.
311 // - Memory to these "arrays" is allocated in _S_initialize()
312 // for _S_max_threads + global pool 0.
316 // Each bin has its own mutex which is used to ensure data
317 // integrity while changing "ownership" on a block. The mutex
318 // is initialized in _S_initialize().
319 __gthread_mutex_t* _M_mutex;
322 // XXX GLIBCXX_ABI Deprecated
324 _M_initialize(__destroy_handler);
329 if (__builtin_expect(_M_init == false, false))
334 _M_destroy() throw();
337 _M_reserve_block(size_t __bytes, const size_t __thread_id);
340 _M_reclaim_block(char* __p, size_t __bytes);
343 _M_get_bin(size_t __which)
344 { return _M_bin[__which]; }
347 _M_adjust_freelist(const _Bin_record& __bin, _Block_record* __block,
350 if (__gthread_active_p())
352 __block->_M_thread_id = __thread_id;
353 --__bin._M_free[__thread_id];
354 ++__bin._M_used[__thread_id];
358 // XXX GLIBCXX_ABI Deprecated
360 _M_destroy_thread_key(void*);
366 : _M_bin(NULL), _M_bin_size(1), _M_thread_freelist(NULL)
369 explicit __pool(const __pool_base::_Tune& __tune)
370 : __pool_base(__tune), _M_bin(NULL), _M_bin_size(1),
371 _M_thread_freelist(NULL)
375 // An "array" of bin_records each of which represents a specific
376 // power of 2 size. Memory to this "array" is allocated in
380 // Actual value calculated in _M_initialize().
383 _Thread_record* _M_thread_freelist;
384 void* _M_thread_freelist_initial;
391 template<template <bool> class _PoolTp, bool _Thread>
394 typedef _PoolTp<_Thread> pool_type;
399 static pool_type _S_pool;
404 template<template <bool> class _PoolTp, bool _Thread>
405 struct __common_pool_base;
407 template<template <bool> class _PoolTp>
408 struct __common_pool_base<_PoolTp, false>
409 : public __common_pool<_PoolTp, false>
411 using __common_pool<_PoolTp, false>::_S_get_pool;
417 if (__builtin_expect(__init == false, false))
419 _S_get_pool()._M_initialize_once();
426 template<template <bool> class _PoolTp>
427 struct __common_pool_base<_PoolTp, true>
428 : public __common_pool<_PoolTp, true>
430 using __common_pool<_PoolTp, true>::_S_get_pool;
434 { _S_get_pool()._M_initialize_once(); }
440 if (__builtin_expect(__init == false, false))
442 if (__gthread_active_p())
444 // On some platforms, __gthread_once_t is an aggregate.
445 static __gthread_once_t __once = __GTHREAD_ONCE_INIT;
446 __gthread_once(&__once, _S_initialize);
449 // Double check initialization. May be necessary on some
450 // systems for proper construction when not compiling with
452 _S_get_pool()._M_initialize_once();
459 /// Policy for shared __pool objects.
460 template<template <bool> class _PoolTp, bool _Thread>
461 struct __common_pool_policy : public __common_pool_base<_PoolTp, _Thread>
463 template<typename _Tp1, template <bool> class _PoolTp1 = _PoolTp,
464 bool _Thread1 = _Thread>
466 { typedef __common_pool_policy<_PoolTp1, _Thread1> other; };
468 using __common_pool_base<_PoolTp, _Thread>::_S_get_pool;
469 using __common_pool_base<_PoolTp, _Thread>::_S_initialize_once;
473 template<typename _Tp, template <bool> class _PoolTp, bool _Thread>
474 struct __per_type_pool
476 typedef _Tp value_type;
477 typedef _PoolTp<_Thread> pool_type;
482 // Sane defaults for the _PoolTp.
483 typedef typename pool_type::_Block_record _Block_record;
484 const static size_t __a = (__alignof__(_Tp) >= sizeof(_Block_record)
485 ? __alignof__(_Tp) : sizeof(_Block_record));
487 typedef typename __pool_base::_Tune _Tune;
488 static _Tune _S_tune(__a, sizeof(_Tp) * 64,
489 sizeof(_Tp) * 2 >= __a ? sizeof(_Tp) * 2 : __a,
490 sizeof(_Tp) * size_t(_Tune::_S_chunk_size),
491 _Tune::_S_max_threads,
492 _Tune::_S_freelist_headroom,
493 std::getenv("GLIBCXX_FORCE_NEW") ? true : false);
494 static pool_type _S_pool(_S_tune);
499 template<typename _Tp, template <bool> class _PoolTp, bool _Thread>
500 struct __per_type_pool_base;
502 template<typename _Tp, template <bool> class _PoolTp>
503 struct __per_type_pool_base<_Tp, _PoolTp, false>
504 : public __per_type_pool<_Tp, _PoolTp, false>
506 using __per_type_pool<_Tp, _PoolTp, false>::_S_get_pool;
512 if (__builtin_expect(__init == false, false))
514 _S_get_pool()._M_initialize_once();
521 template<typename _Tp, template <bool> class _PoolTp>
522 struct __per_type_pool_base<_Tp, _PoolTp, true>
523 : public __per_type_pool<_Tp, _PoolTp, true>
525 using __per_type_pool<_Tp, _PoolTp, true>::_S_get_pool;
529 { _S_get_pool()._M_initialize_once(); }
535 if (__builtin_expect(__init == false, false))
537 if (__gthread_active_p())
539 // On some platforms, __gthread_once_t is an aggregate.
540 static __gthread_once_t __once = __GTHREAD_ONCE_INIT;
541 __gthread_once(&__once, _S_initialize);
544 // Double check initialization. May be necessary on some
545 // systems for proper construction when not compiling with
547 _S_get_pool()._M_initialize_once();
554 /// Policy for individual __pool objects.
555 template<typename _Tp, template <bool> class _PoolTp, bool _Thread>
556 struct __per_type_pool_policy
557 : public __per_type_pool_base<_Tp, _PoolTp, _Thread>
559 template<typename _Tp1, template <bool> class _PoolTp1 = _PoolTp,
560 bool _Thread1 = _Thread>
562 { typedef __per_type_pool_policy<_Tp1, _PoolTp1, _Thread1> other; };
564 using __per_type_pool_base<_Tp, _PoolTp, _Thread>::_S_get_pool;
565 using __per_type_pool_base<_Tp, _PoolTp, _Thread>::_S_initialize_once;
569 /// Base class for _Tp dependent member functions.
570 template<typename _Tp>
571 class __mt_alloc_base
574 typedef size_t size_type;
575 typedef ptrdiff_t difference_type;
576 typedef _Tp* pointer;
577 typedef const _Tp* const_pointer;
578 typedef _Tp& reference;
579 typedef const _Tp& const_reference;
580 typedef _Tp value_type;
583 address(reference __x) const
587 address(const_reference __x) const
591 max_size() const throw()
592 { return size_t(-1) / sizeof(_Tp); }
594 // _GLIBCXX_RESOLVE_LIB_DEFECTS
595 // 402. wrong new expression in [some_] allocator::construct
597 construct(pointer __p, const _Tp& __val)
598 { ::new((void *)__p) _Tp(__val); }
600 #ifdef __GXX_EXPERIMENTAL_CXX0X__
601 template<typename... _Args>
603 construct(pointer __p, _Args&&... __args)
604 { ::new((void *)__p) _Tp(std::forward<_Args>(__args)...); }
608 destroy(pointer __p) { __p->~_Tp(); }
612 #define __thread_default true
614 #define __thread_default false
618 * @brief This is a fixed size (power of 2) allocator which - when
619 * compiled with thread support - will maintain one freelist per
620 * size per thread plus a "global" one. Steps are taken to limit
621 * the per thread freelist sizes (by returning excess back to
622 * the "global" list).
623 * @ingroup allocators
626 * http://gcc.gnu.org/onlinedocs/libstdc++/manual/bk01pt12ch32.html
628 template<typename _Tp,
629 typename _Poolp = __common_pool_policy<__pool, __thread_default> >
630 class __mt_alloc : public __mt_alloc_base<_Tp>
633 typedef size_t size_type;
634 typedef ptrdiff_t difference_type;
635 typedef _Tp* pointer;
636 typedef const _Tp* const_pointer;
637 typedef _Tp& reference;
638 typedef const _Tp& const_reference;
639 typedef _Tp value_type;
640 typedef _Poolp __policy_type;
641 typedef typename _Poolp::pool_type __pool_type;
643 template<typename _Tp1, typename _Poolp1 = _Poolp>
646 typedef typename _Poolp1::template _M_rebind<_Tp1>::other pol_type;
647 typedef __mt_alloc<_Tp1, pol_type> other;
650 __mt_alloc() throw() { }
652 __mt_alloc(const __mt_alloc&) throw() { }
654 template<typename _Tp1, typename _Poolp1>
655 __mt_alloc(const __mt_alloc<_Tp1, _Poolp1>&) throw() { }
657 ~__mt_alloc() throw() { }
660 allocate(size_type __n, const void* = 0);
663 deallocate(pointer __p, size_type __n);
665 const __pool_base::_Tune
668 // Return a copy, not a reference, for external consumption.
669 return __policy_type::_S_get_pool()._M_get_options();
673 _M_set_options(__pool_base::_Tune __t)
674 { __policy_type::_S_get_pool()._M_set_options(__t); }
677 template<typename _Tp, typename _Poolp>
678 typename __mt_alloc<_Tp, _Poolp>::pointer
679 __mt_alloc<_Tp, _Poolp>::
680 allocate(size_type __n, const void*)
682 if (__builtin_expect(__n > this->max_size(), false))
683 std::__throw_bad_alloc();
685 __policy_type::_S_initialize_once();
687 // Requests larger than _M_max_bytes are handled by operator
688 // new/delete directly.
689 __pool_type& __pool = __policy_type::_S_get_pool();
690 const size_t __bytes = __n * sizeof(_Tp);
691 if (__pool._M_check_threshold(__bytes))
693 void* __ret = ::operator new(__bytes);
694 return static_cast<_Tp*>(__ret);
697 // Round up to power of 2 and figure out which bin to use.
698 const size_t __which = __pool._M_get_binmap(__bytes);
699 const size_t __thread_id = __pool._M_get_thread_id();
701 // Find out if we have blocks on our freelist. If so, go ahead
702 // and use them directly without having to lock anything.
704 typedef typename __pool_type::_Bin_record _Bin_record;
705 const _Bin_record& __bin = __pool._M_get_bin(__which);
706 if (__bin._M_first[__thread_id])
709 typedef typename __pool_type::_Block_record _Block_record;
710 _Block_record* __block = __bin._M_first[__thread_id];
711 __bin._M_first[__thread_id] = __block->_M_next;
713 __pool._M_adjust_freelist(__bin, __block, __thread_id);
714 __c = reinterpret_cast<char*>(__block) + __pool._M_get_align();
719 __c = __pool._M_reserve_block(__bytes, __thread_id);
721 return static_cast<_Tp*>(static_cast<void*>(__c));
724 template<typename _Tp, typename _Poolp>
726 __mt_alloc<_Tp, _Poolp>::
727 deallocate(pointer __p, size_type __n)
729 if (__builtin_expect(__p != 0, true))
731 // Requests larger than _M_max_bytes are handled by
732 // operators new/delete directly.
733 __pool_type& __pool = __policy_type::_S_get_pool();
734 const size_t __bytes = __n * sizeof(_Tp);
735 if (__pool._M_check_threshold(__bytes))
736 ::operator delete(__p);
738 __pool._M_reclaim_block(reinterpret_cast<char*>(__p), __bytes);
742 template<typename _Tp, typename _Poolp>
744 operator==(const __mt_alloc<_Tp, _Poolp>&, const __mt_alloc<_Tp, _Poolp>&)
747 template<typename _Tp, typename _Poolp>
749 operator!=(const __mt_alloc<_Tp, _Poolp>&, const __mt_alloc<_Tp, _Poolp>&)
752 #undef __thread_default
754 _GLIBCXX_END_NAMESPACE