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, 59 Temple Place - Suite 330, Boston, MA 02111-1307,
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*);
46 typedef void (*__create_handler)(void);
48 /// @brief Base class for pool object.
51 // Using short int as type for the binmap implies we are never
52 // caching blocks larger than 65535 with this allocator.
53 typedef unsigned short int _Binmap_type;
55 // Variables used to configure the behavior of the allocator,
56 // assigned and explained in detail below.
59 // Compile time constants for the default _Tune values.
60 enum { _S_align = 8 };
61 enum { _S_max_bytes = 128 };
62 enum { _S_min_bin = 8 };
63 enum { _S_chunk_size = 4096 - 4 * sizeof(void*) };
64 enum { _S_max_threads = 4096 };
65 enum { _S_freelist_headroom = 10 };
68 // NB: In any case must be >= sizeof(_Block_record), that
69 // is 4 on 32 bit machines and 8 on 64 bit machines.
72 // Allocation requests (after round-up to power of 2) below
73 // this value will be handled by the allocator. A raw new/
74 // call will be used for requests larger than this value.
77 // Size in bytes of the smallest bin.
78 // NB: Must be a power of 2 and >= _M_align.
81 // In order to avoid fragmenting and minimize the number of
82 // new() calls we always request new memory using this
83 // value. Based on previous discussions on the libstdc++
84 // mailing list we have choosen the value below.
85 // See http://gcc.gnu.org/ml/libstdc++/2001-07/msg00077.html
88 // The maximum number of supported threads. For
89 // single-threaded operation, use one. Maximum values will
90 // vary depending on details of the underlying system. (For
91 // instance, Linux 2.4.18 reports 4070 in
92 // /proc/sys/kernel/threads-max, while Linux 2.6.6 reports
94 size_t _M_max_threads;
96 // Each time a deallocation occurs in a threaded application
97 // we make sure that there are no more than
98 // _M_freelist_headroom % of used memory on the freelist. If
99 // the number of additional records is more than
100 // _M_freelist_headroom % of the freelist, we move these
101 // records back to the global pool.
102 size_t _M_freelist_headroom;
104 // Set to true forces all allocations to use new().
109 : _M_align(_S_align), _M_max_bytes(_S_max_bytes), _M_min_bin(_S_min_bin),
110 _M_chunk_size(_S_chunk_size), _M_max_threads(_S_max_threads),
111 _M_freelist_headroom(_S_freelist_headroom),
112 _M_force_new(getenv("GLIBCXX_FORCE_NEW") ? true : false)
116 _Tune(size_t __align, size_t __maxb, size_t __minbin, size_t __chunk,
117 size_t __maxthreads, size_t __headroom, bool __force)
118 : _M_align(__align), _M_max_bytes(__maxb), _M_min_bin(__minbin),
119 _M_chunk_size(__chunk), _M_max_threads(__maxthreads),
120 _M_freelist_headroom(__headroom), _M_force_new(__force)
124 struct _Block_address
127 _Block_address* _M_next;
131 _M_get_options() const
132 { return _M_options; }
135 _M_set_options(_Tune __t)
142 _M_check_threshold(size_t __bytes)
143 { return __bytes > _M_options._M_max_bytes || _M_options._M_force_new; }
146 _M_get_binmap(size_t __bytes)
147 { return _M_binmap[__bytes]; }
151 { return _M_options._M_align; }
155 : _M_options(_Tune()), _M_binmap(NULL), _M_init(false) { }
158 __pool_base(const _Tune& __options)
159 : _M_options(__options), _M_binmap(NULL), _M_init(false) { }
163 __pool_base(const __pool_base&);
166 operator=(const __pool_base&);
169 // Configuration options.
172 _Binmap_type* _M_binmap;
174 // Configuration of the pool object via _M_options can happen
175 // after construction but before initialization. After
176 // initialization is complete, this variable is set to true.
182 * @brief Data describing the underlying memory pool, parameterized on
185 template<bool _Thread>
194 /// Specialization for single thread.
196 class __pool<false> : public __pool_base
201 // Points to the block_record of the next free block.
202 _Block_record* volatile _M_next;
207 // An "array" of pointers to the first free block.
208 _Block_record** volatile _M_first;
210 // A list of the initial addresses of all allocated blocks.
211 _Block_address* _M_address;
217 if (__builtin_expect(_M_init == false, false))
222 _M_destroy() throw();
225 _M_reserve_block(size_t __bytes, const size_t __thread_id);
228 _M_reclaim_block(char* __p, size_t __bytes);
231 _M_get_thread_id() { return 0; }
234 _M_get_bin(size_t __which)
235 { return _M_bin[__which]; }
238 _M_adjust_freelist(const _Bin_record&, _Block_record*, size_t)
242 : _M_bin(NULL), _M_bin_size(1) { }
244 explicit __pool(const __pool_base::_Tune& __tune)
245 : __pool_base(__tune), _M_bin(NULL), _M_bin_size(1) { }
248 // An "array" of bin_records each of which represents a specific
249 // power of 2 size. Memory to this "array" is allocated in
251 _Bin_record* volatile _M_bin;
253 // Actual value calculated in _M_initialize().
261 /// Specialization for thread enabled, via gthreads.h.
263 class __pool<true> : public __pool_base
266 // Each requesting thread is assigned an id ranging from 1 to
267 // _S_max_threads. Thread id 0 is used as a global memory pool.
268 // In order to get constant performance on the thread assignment
269 // routine, we keep a list of free ids. When a thread first
270 // requests memory we remove the first record in this list and
271 // stores the address in a __gthread_key. When initializing the
272 // __gthread_key we specify a destructor. When this destructor
273 // (i.e. the thread dies) is called, we return the thread id to
274 // the front of this list.
275 struct _Thread_record
277 // Points to next free thread id record. NULL if last record in list.
278 _Thread_record* volatile _M_next;
280 // Thread id ranging from 1 to _S_max_threads.
286 // Points to the block_record of the next free block.
287 _Block_record* volatile _M_next;
289 // The thread id of the thread which has requested this block.
295 // An "array" of pointers to the first free block for each
296 // thread id. Memory to this "array" is allocated in
297 // _S_initialize() for _S_max_threads + global pool 0.
298 _Block_record** volatile _M_first;
300 // A list of the initial addresses of all allocated blocks.
301 _Block_address* _M_address;
303 // An "array" of counters used to keep track of the amount of
304 // blocks that are on the freelist/used for each thread id.
305 // Memory to these "arrays" is allocated in _S_initialize() for
306 // _S_max_threads + global pool 0.
307 size_t* volatile _M_free;
308 size_t* volatile _M_used;
310 // Each bin has its own mutex which is used to ensure data
311 // integrity while changing "ownership" on a block. The mutex
312 // is initialized in _S_initialize().
313 __gthread_mutex_t* _M_mutex;
317 _M_initialize(__destroy_handler __d);
320 _M_initialize_once(__create_handler __c)
322 // Although the test in __gthread_once() would suffice, we
323 // wrap test of the once condition in our own unlocked
324 // check. This saves one function call to pthread_once()
325 // (which itself only tests for the once value unlocked anyway
326 // and immediately returns if set)
327 if (__builtin_expect(_M_init == false, false))
329 if (__gthread_active_p())
330 __gthread_once(&_M_once, __c);
337 _M_destroy() throw();
340 _M_reserve_block(size_t __bytes, const size_t __thread_id);
343 _M_reclaim_block(char* __p, size_t __bytes);
346 _M_get_bin(size_t __which)
347 { return _M_bin[__which]; }
350 _M_adjust_freelist(const _Bin_record& __bin, _Block_record* __block,
353 if (__gthread_active_p())
355 __block->_M_thread_id = __thread_id;
356 --__bin._M_free[__thread_id];
357 ++__bin._M_used[__thread_id];
362 _M_destroy_thread_key(void* __freelist_pos);
368 : _M_bin(NULL), _M_bin_size(1), _M_thread_freelist(NULL)
370 // On some platforms, __gthread_once_t is an aggregate.
371 __gthread_once_t __tmp = __GTHREAD_ONCE_INIT;
375 explicit __pool(const __pool_base::_Tune& __tune)
376 : __pool_base(__tune), _M_bin(NULL), _M_bin_size(1),
377 _M_thread_freelist(NULL)
379 // On some platforms, __gthread_once_t is an aggregate.
380 __gthread_once_t __tmp = __GTHREAD_ONCE_INIT;
385 // An "array" of bin_records each of which represents a specific
386 // power of 2 size. Memory to this "array" is allocated in
388 _Bin_record* volatile _M_bin;
390 // Actual value calculated in _M_initialize().
393 __gthread_once_t _M_once;
395 _Thread_record* _M_thread_freelist;
396 void* _M_thread_freelist_initial;
401 /// @brief Policy for shared __pool objects.
402 template<template <bool> class _PoolTp, bool _Thread>
403 struct __common_pool_policy;
405 /// Partial specialization for single thread.
406 template<template <bool> class _PoolTp>
407 struct __common_pool_policy<_PoolTp, false>
409 typedef _PoolTp<false> pool_type;
411 template<typename _Tp1, template <bool> class _PoolTp1 = _PoolTp,
412 bool _Thread1 = false>
414 { typedef __common_pool_policy<_PoolTp1, _Thread1> other; };
419 static pool_type _S_pool;
427 if (__builtin_expect(__init == false, false))
429 _S_get_pool()._M_initialize_once();
436 /// Partial specialization for thread enabled, via gthreads.h.
437 template<template <bool> class _PoolTp>
438 struct __common_pool_policy<_PoolTp, true>
440 typedef _PoolTp<true> pool_type;
442 template<typename _Tp1, template <bool> class _PoolTp1 = _PoolTp,
443 bool _Thread1 = true>
445 { typedef __common_pool_policy<_PoolTp1, _Thread1> other; };
450 static pool_type _S_pool;
458 if (__builtin_expect(__init == false, false))
460 _S_get_pool()._M_initialize_once(_S_initialize);
467 _S_destroy_thread_key(void* __freelist_pos)
468 { _S_get_pool()._M_destroy_thread_key(__freelist_pos); }
472 { _S_get_pool()._M_initialize(_S_destroy_thread_key); }
477 /// @brief Policy for individual __pool objects.
478 template<typename _Tp, template <bool> class _PoolTp, bool _Thread>
479 struct __per_type_pool_policy;
481 /// Partial specialization for single thread.
482 template<typename _Tp, template <bool> class _PoolTp>
483 struct __per_type_pool_policy<_Tp, _PoolTp, false>
485 typedef _Tp value_type;
486 typedef _PoolTp<false> pool_type;
488 template<typename _Tp1, template <bool> class _PoolTp1 = _PoolTp,
489 bool _Thread1 = false>
491 { typedef __per_type_pool_policy<_Tp1, _PoolTp1, _Thread1> other; };
496 // Sane defaults for the _PoolTp.
497 typedef typename pool_type::_Block_record _Block_record;
498 const static size_t __align = (__alignof__(_Tp) >= sizeof(_Block_record)
500 : sizeof(_Block_record));
502 typedef typename __pool_base::_Tune _Tune;
503 static _Tune _S_tune(__align, sizeof(_Tp) * 64,
504 sizeof(_Tp) * 2 >= __align ? sizeof(_Tp) * 2
506 sizeof(_Tp) * size_t(_Tune::_S_chunk_size),
507 _Tune::_S_max_threads,
508 _Tune::_S_freelist_headroom,
509 getenv("GLIBCXX_FORCE_NEW") ? true : false);
510 static pool_type _S_pool(_S_tune);
518 if (__builtin_expect(__init == false, false))
520 _S_get_pool()._M_initialize_once();
527 /// Partial specialization for thread enabled, via gthreads.h.
528 template<typename _Tp, template <bool> class _PoolTp>
529 struct __per_type_pool_policy<_Tp, _PoolTp, true>
531 typedef _Tp value_type;
532 typedef _PoolTp<true> pool_type;
534 template<typename _Tp1, template <bool> class _PoolTp1 = _PoolTp,
535 bool _Thread1 = true>
537 { typedef __per_type_pool_policy<_Tp1, _PoolTp1, _Thread1> other; };
542 // Sane defaults for the _PoolTp.
543 typedef typename pool_type::_Block_record _Block_record;
544 const static size_t __align = (__alignof__(_Tp) >= sizeof(_Block_record)
546 : sizeof(_Block_record));
548 typedef typename __pool_base::_Tune _Tune;
549 static _Tune _S_tune(__align, sizeof(_Tp) * 64,
550 sizeof(_Tp) * 2 >= __align ? sizeof(_Tp) * 2
552 sizeof(_Tp) * size_t(_Tune::_S_chunk_size),
553 _Tune::_S_max_threads,
554 _Tune::_S_freelist_headroom,
555 getenv("GLIBCXX_FORCE_NEW") ? true : false);
556 static pool_type _S_pool(_S_tune);
564 if (__builtin_expect(__init == false, false))
566 _S_get_pool()._M_initialize_once(_S_initialize);
573 _S_destroy_thread_key(void* __freelist_pos)
574 { _S_get_pool()._M_destroy_thread_key(__freelist_pos); }
578 { _S_get_pool()._M_initialize(_S_destroy_thread_key); }
582 /// @brief Base class for _Tp dependent member functions.
583 template<typename _Tp>
584 class __mt_alloc_base
587 typedef size_t size_type;
588 typedef ptrdiff_t difference_type;
589 typedef _Tp* pointer;
590 typedef const _Tp* const_pointer;
591 typedef _Tp& reference;
592 typedef const _Tp& const_reference;
593 typedef _Tp value_type;
596 address(reference __x) const
600 address(const_reference __x) const
604 max_size() const throw()
605 { return size_t(-1) / sizeof(_Tp); }
607 // _GLIBCXX_RESOLVE_LIB_DEFECTS
608 // 402. wrong new expression in [some_] allocator::construct
610 construct(pointer __p, const _Tp& __val)
611 { ::new(__p) _Tp(__val); }
614 destroy(pointer __p) { __p->~_Tp(); }
618 #define __thread_default true
620 #define __thread_default false
624 * @brief This is a fixed size (power of 2) allocator which - when
625 * compiled with thread support - will maintain one freelist per
626 * size per thread plus a "global" one. Steps are taken to limit
627 * the per thread freelist sizes (by returning excess back to
628 * the "global" list).
631 * http://gcc.gnu.org/onlinedocs/libstdc++/ext/mt_allocator.html
633 template<typename _Tp,
634 typename _Poolp = __common_pool_policy<__pool, __thread_default> >
635 class __mt_alloc : public __mt_alloc_base<_Tp>
638 typedef size_t size_type;
639 typedef ptrdiff_t difference_type;
640 typedef _Tp* pointer;
641 typedef const _Tp* const_pointer;
642 typedef _Tp& reference;
643 typedef const _Tp& const_reference;
644 typedef _Tp value_type;
645 typedef _Poolp __policy_type;
646 typedef typename _Poolp::pool_type __pool_type;
648 template<typename _Tp1, typename _Poolp1 = _Poolp>
651 typedef typename _Poolp1::template _M_rebind<_Tp1>::other pol_type;
652 typedef __mt_alloc<_Tp1, pol_type> other;
656 { __policy_type::_S_get_pool(); }
658 __mt_alloc(const __mt_alloc&) throw()
659 { __policy_type::_S_get_pool(); }
661 template<typename _Tp1, typename _Poolp1>
662 __mt_alloc(const __mt_alloc<_Tp1, _Poolp1>& obj) throw()
663 { __policy_type::_S_get_pool(); }
665 ~__mt_alloc() throw() { }
668 allocate(size_type __n, const void* = 0);
671 deallocate(pointer __p, size_type __n);
673 const __pool_base::_Tune
676 // Return a copy, not a reference, for external consumption.
677 return __policy_type::_S_get_pool()._M_get_options();
681 _M_set_options(__pool_base::_Tune __t)
682 { __policy_type::_S_get_pool()._M_set_options(__t); }
685 template<typename _Tp, typename _Poolp>
686 typename __mt_alloc<_Tp, _Poolp>::pointer
687 __mt_alloc<_Tp, _Poolp>::
688 allocate(size_type __n, const void*)
690 if (__builtin_expect(__n > this->max_size(), false))
691 std::__throw_bad_alloc();
693 __policy_type::_S_initialize_once();
695 // Requests larger than _M_max_bytes are handled by operator
696 // new/delete directly.
697 __pool_type& __pool = __policy_type::_S_get_pool();
698 const size_t __bytes = __n * sizeof(_Tp);
699 if (__pool._M_check_threshold(__bytes))
701 void* __ret = ::operator new(__bytes);
702 return static_cast<_Tp*>(__ret);
705 // Round up to power of 2 and figure out which bin to use.
706 const size_t __which = __pool._M_get_binmap(__bytes);
707 const size_t __thread_id = __pool._M_get_thread_id();
709 // Find out if we have blocks on our freelist. If so, go ahead
710 // and use them directly without having to lock anything.
712 typedef typename __pool_type::_Bin_record _Bin_record;
713 const _Bin_record& __bin = __pool._M_get_bin(__which);
714 if (__bin._M_first[__thread_id])
717 typedef typename __pool_type::_Block_record _Block_record;
718 _Block_record* __block = __bin._M_first[__thread_id];
719 __bin._M_first[__thread_id] = __block->_M_next;
721 __pool._M_adjust_freelist(__bin, __block, __thread_id);
722 __c = reinterpret_cast<char*>(__block) + __pool._M_get_align();
727 __c = __pool._M_reserve_block(__bytes, __thread_id);
729 return static_cast<_Tp*>(static_cast<void*>(__c));
732 template<typename _Tp, typename _Poolp>
734 __mt_alloc<_Tp, _Poolp>::
735 deallocate(pointer __p, size_type __n)
737 if (__builtin_expect(__p != 0, true))
739 // Requests larger than _M_max_bytes are handled by
740 // operators new/delete directly.
741 __pool_type& __pool = __policy_type::_S_get_pool();
742 const size_t __bytes = __n * sizeof(_Tp);
743 if (__pool._M_check_threshold(__bytes))
744 ::operator delete(__p);
746 __pool._M_reclaim_block(reinterpret_cast<char*>(__p), __bytes);
750 template<typename _Tp, typename _Poolp>
752 operator==(const __mt_alloc<_Tp, _Poolp>&, const __mt_alloc<_Tp, _Poolp>&)
755 template<typename _Tp, typename _Poolp>
757 operator!=(const __mt_alloc<_Tp, _Poolp>&, const __mt_alloc<_Tp, _Poolp>&)
760 #undef __thread_default
761 } // namespace __gnu_cxx