1 // MT-optimized allocator -*- C++ -*-
3 // Copyright (C) 2003, 2004, 2005 Free Software Foundation, Inc.
5 // This file is part of the GNU ISO C++ Library. This library is free
6 // software; you can redistribute it and/or modify it under the
7 // terms of the GNU General Public License as published by the
8 // Free Software Foundation; either version 2, or (at your option)
11 // This library is distributed in the hope that it will be useful,
12 // but WITHOUT ANY WARRANTY; without even the implied warranty of
13 // MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
14 // GNU General Public License for more details.
16 // You should have received a copy of the GNU General Public License along
17 // with this library; see the file COPYING. If not, write to the Free
18 // Software Foundation, 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301,
21 // As a special exception, you may use this file as part of a free software
22 // library without restriction. Specifically, if other files instantiate
23 // templates or use macros or inline functions from this file, or you compile
24 // this file and link it with other files to produce an executable, this
25 // file does not by itself cause the resulting executable to be covered by
26 // the GNU General Public License. This exception does not however
27 // invalidate any other reasons why the executable file might be covered by
28 // the GNU General Public License.
30 /** @file ext/mt_allocator.h
31 * This file is a GNU extension to the Standard C++ Library.
34 #ifndef _MT_ALLOCATOR_H
35 #define _MT_ALLOCATOR_H 1
39 #include <bits/functexcept.h>
40 #include <bits/gthr.h>
41 #include <bits/atomicity.h>
45 typedef void (*__destroy_handler)(void*);
47 /// @brief Base class for pool object.
50 // Using short int as type for the binmap implies we are never
51 // caching blocks larger than 65535 with this allocator.
52 typedef unsigned short int _Binmap_type;
54 // Variables used to configure the behavior of the allocator,
55 // assigned and explained in detail below.
58 // Compile time constants for the default _Tune values.
59 enum { _S_align = 8 };
60 enum { _S_max_bytes = 128 };
61 enum { _S_min_bin = 8 };
62 enum { _S_chunk_size = 4096 - 4 * sizeof(void*) };
63 enum { _S_max_threads = 4096 };
64 enum { _S_freelist_headroom = 10 };
67 // NB: In any case must be >= sizeof(_Block_record), that
68 // is 4 on 32 bit machines and 8 on 64 bit machines.
71 // Allocation requests (after round-up to power of 2) below
72 // this value will be handled by the allocator. A raw new/
73 // call will be used for requests larger than this value.
76 // Size in bytes of the smallest bin.
77 // NB: Must be a power of 2 and >= _M_align.
80 // In order to avoid fragmenting and minimize the number of
81 // new() calls we always request new memory using this
82 // value. Based on previous discussions on the libstdc++
83 // mailing list we have choosen the value below.
84 // See http://gcc.gnu.org/ml/libstdc++/2001-07/msg00077.html
87 // The maximum number of supported threads. For
88 // single-threaded operation, use one. Maximum values will
89 // vary depending on details of the underlying system. (For
90 // instance, Linux 2.4.18 reports 4070 in
91 // /proc/sys/kernel/threads-max, while Linux 2.6.6 reports
93 size_t _M_max_threads;
95 // Each time a deallocation occurs in a threaded application
96 // we make sure that there are no more than
97 // _M_freelist_headroom % of used memory on the freelist. If
98 // the number of additional records is more than
99 // _M_freelist_headroom % of the freelist, we move these
100 // records back to the global pool.
101 size_t _M_freelist_headroom;
103 // Set to true forces all allocations to use new().
108 : _M_align(_S_align), _M_max_bytes(_S_max_bytes), _M_min_bin(_S_min_bin),
109 _M_chunk_size(_S_chunk_size), _M_max_threads(_S_max_threads),
110 _M_freelist_headroom(_S_freelist_headroom),
111 _M_force_new(getenv("GLIBCXX_FORCE_NEW") ? true : false)
115 _Tune(size_t __align, size_t __maxb, size_t __minbin, size_t __chunk,
116 size_t __maxthreads, size_t __headroom, bool __force)
117 : _M_align(__align), _M_max_bytes(__maxb), _M_min_bin(__minbin),
118 _M_chunk_size(__chunk), _M_max_threads(__maxthreads),
119 _M_freelist_headroom(__headroom), _M_force_new(__force)
123 struct _Block_address
126 _Block_address* _M_next;
130 _M_get_options() const
131 { return _M_options; }
134 _M_set_options(_Tune __t)
141 _M_check_threshold(size_t __bytes)
142 { return __bytes > _M_options._M_max_bytes || _M_options._M_force_new; }
145 _M_get_binmap(size_t __bytes)
146 { return _M_binmap[__bytes]; }
150 { return _M_options._M_align; }
154 : _M_options(_Tune()), _M_binmap(NULL), _M_init(false) { }
157 __pool_base(const _Tune& __options)
158 : _M_options(__options), _M_binmap(NULL), _M_init(false) { }
162 __pool_base(const __pool_base&);
165 operator=(const __pool_base&);
168 // Configuration options.
171 _Binmap_type* _M_binmap;
173 // Configuration of the pool object via _M_options can happen
174 // after construction but before initialization. After
175 // initialization is complete, this variable is set to true.
181 * @brief Data describing the underlying memory pool, parameterized on
184 template<bool _Thread>
187 /// Specialization for single thread.
189 class __pool<false> : public __pool_base
194 // Points to the block_record of the next free block.
195 _Block_record* volatile _M_next;
200 // An "array" of pointers to the first free block.
201 _Block_record** volatile _M_first;
203 // A list of the initial addresses of all allocated blocks.
204 _Block_address* _M_address;
210 if (__builtin_expect(_M_init == false, false))
215 _M_destroy() throw();
218 _M_reserve_block(size_t __bytes, const size_t __thread_id);
221 _M_reclaim_block(char* __p, size_t __bytes);
224 _M_get_thread_id() { return 0; }
227 _M_get_bin(size_t __which)
228 { return _M_bin[__which]; }
231 _M_adjust_freelist(const _Bin_record&, _Block_record*, size_t)
235 : _M_bin(NULL), _M_bin_size(1) { }
237 explicit __pool(const __pool_base::_Tune& __tune)
238 : __pool_base(__tune), _M_bin(NULL), _M_bin_size(1) { }
241 // An "array" of bin_records each of which represents a specific
242 // power of 2 size. Memory to this "array" is allocated in
244 _Bin_record* volatile _M_bin;
246 // Actual value calculated in _M_initialize().
254 /// Specialization for thread enabled, via gthreads.h.
256 class __pool<true> : public __pool_base
259 // Each requesting thread is assigned an id ranging from 1 to
260 // _S_max_threads. Thread id 0 is used as a global memory pool.
261 // In order to get constant performance on the thread assignment
262 // routine, we keep a list of free ids. When a thread first
263 // requests memory we remove the first record in this list and
264 // stores the address in a __gthread_key. When initializing the
265 // __gthread_key we specify a destructor. When this destructor
266 // (i.e. the thread dies) is called, we return the thread id to
267 // the front of this list.
268 struct _Thread_record
270 // Points to next free thread id record. NULL if last record in list.
271 _Thread_record* volatile _M_next;
273 // Thread id ranging from 1 to _S_max_threads.
279 // Points to the block_record of the next free block.
280 _Block_record* volatile _M_next;
282 // The thread id of the thread which has requested this block.
288 // An "array" of pointers to the first free block for each
289 // thread id. Memory to this "array" is allocated in
290 // _S_initialize() for _S_max_threads + global pool 0.
291 _Block_record** volatile _M_first;
293 // A list of the initial addresses of all allocated blocks.
294 _Block_address* _M_address;
296 // An "array" of counters used to keep track of the amount of
297 // blocks that are on the freelist/used for each thread id.
298 // Memory to these "arrays" is allocated in _S_initialize() for
299 // _S_max_threads + global pool 0.
300 size_t* volatile _M_free;
301 size_t* volatile _M_used;
303 // Each bin has its own mutex which is used to ensure data
304 // integrity while changing "ownership" on a block. The mutex
305 // is initialized in _S_initialize().
306 __gthread_mutex_t* _M_mutex;
309 // XXX GLIBCXX_ABI Deprecated
311 _M_initialize(__destroy_handler);
316 if (__builtin_expect(_M_init == false, false))
321 _M_destroy() throw();
324 _M_reserve_block(size_t __bytes, const size_t __thread_id);
327 _M_reclaim_block(char* __p, size_t __bytes);
330 _M_get_bin(size_t __which)
331 { return _M_bin[__which]; }
334 _M_adjust_freelist(const _Bin_record& __bin, _Block_record* __block,
337 if (__gthread_active_p())
339 __block->_M_thread_id = __thread_id;
340 --__bin._M_free[__thread_id];
341 ++__bin._M_used[__thread_id];
345 // XXX GLIBCXX_ABI Deprecated
347 _M_destroy_thread_key(void*);
353 : _M_bin(NULL), _M_bin_size(1), _M_thread_freelist(NULL)
356 explicit __pool(const __pool_base::_Tune& __tune)
357 : __pool_base(__tune), _M_bin(NULL), _M_bin_size(1),
358 _M_thread_freelist(NULL)
362 // An "array" of bin_records each of which represents a specific
363 // power of 2 size. Memory to this "array" is allocated in
365 _Bin_record* volatile _M_bin;
367 // Actual value calculated in _M_initialize().
370 _Thread_record* _M_thread_freelist;
371 void* _M_thread_freelist_initial;
378 template<template <bool> class _PoolTp, bool _Thread>
381 typedef _PoolTp<_Thread> pool_type;
386 static pool_type _S_pool;
391 template<template <bool> class _PoolTp, bool _Thread>
392 struct __common_pool_base;
394 template<template <bool> class _PoolTp>
395 struct __common_pool_base<_PoolTp, false>
396 : public __common_pool<_PoolTp, false>
398 using __common_pool<_PoolTp, false>::_S_get_pool;
404 if (__builtin_expect(__init == false, false))
406 _S_get_pool()._M_initialize_once();
413 template<template <bool> class _PoolTp>
414 struct __common_pool_base<_PoolTp, true>
415 : public __common_pool<_PoolTp, true>
417 using __common_pool<_PoolTp, true>::_S_get_pool;
421 { _S_get_pool()._M_initialize_once(); }
427 if (__builtin_expect(__init == false, false))
429 if (__gthread_active_p())
431 // On some platforms, __gthread_once_t is an aggregate.
432 static __gthread_once_t __once = __GTHREAD_ONCE_INIT;
433 __gthread_once(&__once, _S_initialize);
436 // Double check initialization. May be necessary on some
437 // systems for proper construction when not compiling with
439 _S_get_pool()._M_initialize_once();
446 /// @brief Policy for shared __pool objects.
447 template<template <bool> class _PoolTp, bool _Thread>
448 struct __common_pool_policy : public __common_pool_base<_PoolTp, _Thread>
450 template<typename _Tp1, template <bool> class _PoolTp1 = _PoolTp,
451 bool _Thread1 = _Thread>
453 { typedef __common_pool_policy<_PoolTp1, _Thread1> other; };
455 using __common_pool_base<_PoolTp, _Thread>::_S_get_pool;
456 using __common_pool_base<_PoolTp, _Thread>::_S_initialize_once;
460 template<typename _Tp, template <bool> class _PoolTp, bool _Thread>
461 struct __per_type_pool
463 typedef _Tp value_type;
464 typedef _PoolTp<_Thread> pool_type;
469 // Sane defaults for the _PoolTp.
470 typedef typename pool_type::_Block_record _Block_record;
471 const static size_t __a = (__alignof__(_Tp) >= sizeof(_Block_record)
472 ? __alignof__(_Tp) : sizeof(_Block_record));
474 typedef typename __pool_base::_Tune _Tune;
475 static _Tune _S_tune(__a, sizeof(_Tp) * 64,
476 sizeof(_Tp) * 2 >= __a ? sizeof(_Tp) * 2 : __a,
477 sizeof(_Tp) * size_t(_Tune::_S_chunk_size),
478 _Tune::_S_max_threads,
479 _Tune::_S_freelist_headroom,
480 getenv("GLIBCXX_FORCE_NEW") ? true : false);
481 static pool_type _S_pool(_S_tune);
486 template<typename _Tp, template <bool> class _PoolTp, bool _Thread>
487 struct __per_type_pool_base;
489 template<typename _Tp, template <bool> class _PoolTp>
490 struct __per_type_pool_base<_Tp, _PoolTp, false>
491 : public __per_type_pool<_Tp, _PoolTp, false>
493 using __per_type_pool<_Tp, _PoolTp, false>::_S_get_pool;
499 if (__builtin_expect(__init == false, false))
501 _S_get_pool()._M_initialize_once();
508 template<typename _Tp, template <bool> class _PoolTp>
509 struct __per_type_pool_base<_Tp, _PoolTp, true>
510 : public __per_type_pool<_Tp, _PoolTp, true>
512 using __per_type_pool<_Tp, _PoolTp, true>::_S_get_pool;
516 { _S_get_pool()._M_initialize_once(); }
522 if (__builtin_expect(__init == false, false))
524 if (__gthread_active_p())
526 // On some platforms, __gthread_once_t is an aggregate.
527 static __gthread_once_t __once = __GTHREAD_ONCE_INIT;
528 __gthread_once(&__once, _S_initialize);
531 // Double check initialization. May be necessary on some
532 // systems for proper construction when not compiling with
534 _S_get_pool()._M_initialize_once();
541 /// @brief Policy for individual __pool objects.
542 template<typename _Tp, template <bool> class _PoolTp, bool _Thread>
543 struct __per_type_pool_policy
544 : public __per_type_pool_base<_Tp, _PoolTp, _Thread>
546 template<typename _Tp1, template <bool> class _PoolTp1 = _PoolTp,
547 bool _Thread1 = _Thread>
549 { typedef __per_type_pool_policy<_Tp1, _PoolTp1, _Thread1> other; };
551 using __per_type_pool_base<_Tp, _PoolTp, _Thread>::_S_get_pool;
552 using __per_type_pool_base<_Tp, _PoolTp, _Thread>::_S_initialize_once;
556 /// @brief Base class for _Tp dependent member functions.
557 template<typename _Tp>
558 class __mt_alloc_base
561 typedef size_t size_type;
562 typedef ptrdiff_t difference_type;
563 typedef _Tp* pointer;
564 typedef const _Tp* const_pointer;
565 typedef _Tp& reference;
566 typedef const _Tp& const_reference;
567 typedef _Tp value_type;
570 address(reference __x) const
574 address(const_reference __x) const
578 max_size() const throw()
579 { return size_t(-1) / sizeof(_Tp); }
581 // _GLIBCXX_RESOLVE_LIB_DEFECTS
582 // 402. wrong new expression in [some_] allocator::construct
584 construct(pointer __p, const _Tp& __val)
585 { ::new(__p) _Tp(__val); }
588 destroy(pointer __p) { __p->~_Tp(); }
592 #define __thread_default true
594 #define __thread_default false
598 * @brief This is a fixed size (power of 2) allocator which - when
599 * compiled with thread support - will maintain one freelist per
600 * size per thread plus a "global" one. Steps are taken to limit
601 * the per thread freelist sizes (by returning excess back to
602 * the "global" list).
605 * http://gcc.gnu.org/onlinedocs/libstdc++/ext/mt_allocator.html
607 template<typename _Tp,
608 typename _Poolp = __common_pool_policy<__pool, __thread_default> >
609 class __mt_alloc : public __mt_alloc_base<_Tp>
612 typedef size_t size_type;
613 typedef ptrdiff_t difference_type;
614 typedef _Tp* pointer;
615 typedef const _Tp* const_pointer;
616 typedef _Tp& reference;
617 typedef const _Tp& const_reference;
618 typedef _Tp value_type;
619 typedef _Poolp __policy_type;
620 typedef typename _Poolp::pool_type __pool_type;
622 template<typename _Tp1, typename _Poolp1 = _Poolp>
625 typedef typename _Poolp1::template _M_rebind<_Tp1>::other pol_type;
626 typedef __mt_alloc<_Tp1, pol_type> other;
629 __mt_alloc() throw() { }
631 __mt_alloc(const __mt_alloc&) throw() { }
633 template<typename _Tp1, typename _Poolp1>
634 __mt_alloc(const __mt_alloc<_Tp1, _Poolp1>&) throw() { }
636 ~__mt_alloc() throw() { }
639 allocate(size_type __n, const void* = 0);
642 deallocate(pointer __p, size_type __n);
644 const __pool_base::_Tune
647 // Return a copy, not a reference, for external consumption.
648 return __policy_type::_S_get_pool()._M_get_options();
652 _M_set_options(__pool_base::_Tune __t)
653 { __policy_type::_S_get_pool()._M_set_options(__t); }
656 template<typename _Tp, typename _Poolp>
657 typename __mt_alloc<_Tp, _Poolp>::pointer
658 __mt_alloc<_Tp, _Poolp>::
659 allocate(size_type __n, const void*)
661 if (__builtin_expect(__n > this->max_size(), false))
662 std::__throw_bad_alloc();
664 __policy_type::_S_initialize_once();
666 // Requests larger than _M_max_bytes are handled by operator
667 // new/delete directly.
668 __pool_type& __pool = __policy_type::_S_get_pool();
669 const size_t __bytes = __n * sizeof(_Tp);
670 if (__pool._M_check_threshold(__bytes))
672 void* __ret = ::operator new(__bytes);
673 return static_cast<_Tp*>(__ret);
676 // Round up to power of 2 and figure out which bin to use.
677 const size_t __which = __pool._M_get_binmap(__bytes);
678 const size_t __thread_id = __pool._M_get_thread_id();
680 // Find out if we have blocks on our freelist. If so, go ahead
681 // and use them directly without having to lock anything.
683 typedef typename __pool_type::_Bin_record _Bin_record;
684 const _Bin_record& __bin = __pool._M_get_bin(__which);
685 if (__bin._M_first[__thread_id])
688 typedef typename __pool_type::_Block_record _Block_record;
689 _Block_record* __block = __bin._M_first[__thread_id];
690 __bin._M_first[__thread_id] = __block->_M_next;
692 __pool._M_adjust_freelist(__bin, __block, __thread_id);
693 __c = reinterpret_cast<char*>(__block) + __pool._M_get_align();
698 __c = __pool._M_reserve_block(__bytes, __thread_id);
700 return static_cast<_Tp*>(static_cast<void*>(__c));
703 template<typename _Tp, typename _Poolp>
705 __mt_alloc<_Tp, _Poolp>::
706 deallocate(pointer __p, size_type __n)
708 if (__builtin_expect(__p != 0, true))
710 // Requests larger than _M_max_bytes are handled by
711 // operators new/delete directly.
712 __pool_type& __pool = __policy_type::_S_get_pool();
713 const size_t __bytes = __n * sizeof(_Tp);
714 if (__pool._M_check_threshold(__bytes))
715 ::operator delete(__p);
717 __pool._M_reclaim_block(reinterpret_cast<char*>(__p), __bytes);
721 template<typename _Tp, typename _Poolp>
723 operator==(const __mt_alloc<_Tp, _Poolp>&, const __mt_alloc<_Tp, _Poolp>&)
726 template<typename _Tp, typename _Poolp>
728 operator!=(const __mt_alloc<_Tp, _Poolp>&, const __mt_alloc<_Tp, _Poolp>&)
731 #undef __thread_default
732 } // namespace __gnu_cxx