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// MT-optimized allocator -*- C++ -*- // Copyright (C) 2003, 2004, 2005, 2006, 2007, 2008, 2009, 2010 // Free Software Foundation, Inc. // // This file is part of the GNU ISO C++ Library. This library is free // software; you can redistribute it and/or modify it under the // terms of the GNU General Public License as published by the // Free Software Foundation; either version 3, or (at your option) // any later version. // This library is distributed in the hope that it will be useful, // but WITHOUT ANY WARRANTY; without even the implied warranty of // MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the // GNU General Public License for more details. // Under Section 7 of GPL version 3, you are granted additional // permissions described in the GCC Runtime Library Exception, version // 3.1, as published by the Free Software Foundation. // You should have received a copy of the GNU General Public License and // a copy of the GCC Runtime Library Exception along with this program; // see the files COPYING3 and COPYING.RUNTIME respectively. If not, see // <http://www.gnu.org/licenses/>. /** @file ext/mt_allocator.h * This file is a GNU extension to the Standard C++ Library. */ #ifndef _MT_ALLOCATOR_H #define _MT_ALLOCATOR_H 1 #include <new> #include <cstdlib> #include <bits/functexcept.h> #include <ext/atomicity.h> #include <bits/move.h> _GLIBCXX_BEGIN_NAMESPACE(__gnu_cxx) using std::size_t; using std::ptrdiff_t; typedef void (*__destroy_handler)(void*); /// Base class for pool object. struct __pool_base { // Using short int as type for the binmap implies we are never // caching blocks larger than 32768 with this allocator. typedef unsigned short int _Binmap_type; // Variables used to configure the behavior of the allocator, // assigned and explained in detail below. struct _Tune { // Compile time constants for the default _Tune values. enum { _S_align = 8 }; enum { _S_max_bytes = 128 }; enum { _S_min_bin = 8 }; enum { _S_chunk_size = 4096 - 4 * sizeof(void*) }; enum { _S_max_threads = 4096 }; enum { _S_freelist_headroom = 10 }; // Alignment needed. // NB: In any case must be >= sizeof(_Block_record), that // is 4 on 32 bit machines and 8 on 64 bit machines. size_t _M_align; // Allocation requests (after round-up to power of 2) below // this value will be handled by the allocator. A raw new/ // call will be used for requests larger than this value. // NB: Must be much smaller than _M_chunk_size and in any // case <= 32768. size_t _M_max_bytes; // Size in bytes of the smallest bin. // NB: Must be a power of 2 and >= _M_align (and of course // much smaller than _M_max_bytes). size_t _M_min_bin; // In order to avoid fragmenting and minimize the number of // new() calls we always request new memory using this // value. Based on previous discussions on the libstdc++ // mailing list we have chosen the value below. // See http://gcc.gnu.org/ml/libstdc++/2001-07/msg00077.html // NB: At least one order of magnitude > _M_max_bytes. size_t _M_chunk_size; // The maximum number of supported threads. For // single-threaded operation, use one. Maximum values will // vary depending on details of the underlying system. (For // instance, Linux 2.4.18 reports 4070 in // /proc/sys/kernel/threads-max, while Linux 2.6.6 reports // 65534) size_t _M_max_threads; // Each time a deallocation occurs in a threaded application // we make sure that there are no more than // _M_freelist_headroom % of used memory on the freelist. If // the number of additional records is more than // _M_freelist_headroom % of the freelist, we move these // records back to the global pool. size_t _M_freelist_headroom; // Set to true forces all allocations to use new(). bool _M_force_new; explicit _Tune() : _M_align(_S_align), _M_max_bytes(_S_max_bytes), _M_min_bin(_S_min_bin), _M_chunk_size(_S_chunk_size), _M_max_threads(_S_max_threads), _M_freelist_headroom(_S_freelist_headroom), _M_force_new(std::getenv("GLIBCXX_FORCE_NEW") ? true : false) { } explicit _Tune(size_t __align, size_t __maxb, size_t __minbin, size_t __chunk, size_t __maxthreads, size_t __headroom, bool __force) : _M_align(__align), _M_max_bytes(__maxb), _M_min_bin(__minbin), _M_chunk_size(__chunk), _M_max_threads(__maxthreads), _M_freelist_headroom(__headroom), _M_force_new(__force) { } }; struct _Block_address { void* _M_initial; _Block_address* _M_next; }; const _Tune& _M_get_options() const { return _M_options; } void _M_set_options(_Tune __t) { if (!_M_init) _M_options = __t; } bool _M_check_threshold(size_t __bytes) { return __bytes > _M_options._M_max_bytes || _M_options._M_force_new; } size_t _M_get_binmap(size_t __bytes) { return _M_binmap[__bytes]; } size_t _M_get_align() { return _M_options._M_align; } explicit __pool_base() : _M_options(_Tune()), _M_binmap(NULL), _M_init(false) { } explicit __pool_base(const _Tune& __options) : _M_options(__options), _M_binmap(NULL), _M_init(false) { } private: explicit __pool_base(const __pool_base&); __pool_base& operator=(const __pool_base&); protected: // Configuration options. _Tune _M_options; _Binmap_type* _M_binmap; // Configuration of the pool object via _M_options can happen // after construction but before initialization. After // initialization is complete, this variable is set to true. bool _M_init; }; /** * @brief Data describing the underlying memory pool, parameterized on * threading support. */ template<bool _Thread> class __pool; /// Specialization for single thread. template<> class __pool<false> : public __pool_base { public: union _Block_record { // Points to the block_record of the next free block. _Block_record* _M_next; }; struct _Bin_record { // An "array" of pointers to the first free block. _Block_record** _M_first; // A list of the initial addresses of all allocated blocks. _Block_address* _M_address; }; void _M_initialize_once() { if (__builtin_expect(_M_init == false, false)) _M_initialize(); } void _M_destroy() throw(); char* _M_reserve_block(size_t __bytes, const size_t __thread_id); void _M_reclaim_block(char* __p, size_t __bytes) throw (); size_t _M_get_thread_id() { return 0; } const _Bin_record& _M_get_bin(size_t __which) { return _M_bin[__which]; } void _M_adjust_freelist(const _Bin_record&, _Block_record*, size_t) { } explicit __pool() : _M_bin(NULL), _M_bin_size(1) { } explicit __pool(const __pool_base::_Tune& __tune) : __pool_base(__tune), _M_bin(NULL), _M_bin_size(1) { } private: // An "array" of bin_records each of which represents a specific // power of 2 size. Memory to this "array" is allocated in // _M_initialize(). _Bin_record* _M_bin; // Actual value calculated in _M_initialize(). size_t _M_bin_size; void _M_initialize(); }; #ifdef __GTHREADS /// Specialization for thread enabled, via gthreads.h. template<> class __pool<true> : public __pool_base { public: // Each requesting thread is assigned an id ranging from 1 to // _S_max_threads. Thread id 0 is used as a global memory pool. // In order to get constant performance on the thread assignment // routine, we keep a list of free ids. When a thread first // requests memory we remove the first record in this list and // stores the address in a __gthread_key. When initializing the // __gthread_key we specify a destructor. When this destructor // (i.e. the thread dies) is called, we return the thread id to // the front of this list. struct _Thread_record { // Points to next free thread id record. NULL if last record in list. _Thread_record* _M_next; // Thread id ranging from 1 to _S_max_threads. size_t _M_id; }; union _Block_record { // Points to the block_record of the next free block. _Block_record* _M_next; // The thread id of the thread which has requested this block. size_t _M_thread_id; }; struct _Bin_record { // An "array" of pointers to the first free block for each // thread id. Memory to this "array" is allocated in // _S_initialize() for _S_max_threads + global pool 0. _Block_record** _M_first; // A list of the initial addresses of all allocated blocks. _Block_address* _M_address; // An "array" of counters used to keep track of the amount of // blocks that are on the freelist/used for each thread id. // - Note that the second part of the allocated _M_used "array" // actually hosts (atomic) counters of reclaimed blocks: in // _M_reserve_block and in _M_reclaim_block those numbers are // subtracted from the first ones to obtain the actual size // of the "working set" of the given thread. // - Memory to these "arrays" is allocated in _S_initialize() // for _S_max_threads + global pool 0. size_t* _M_free; size_t* _M_used; // Each bin has its own mutex which is used to ensure data // integrity while changing "ownership" on a block. The mutex // is initialized in _S_initialize(). __gthread_mutex_t* _M_mutex; }; // XXX GLIBCXX_ABI Deprecated void _M_initialize(__destroy_handler); void _M_initialize_once() { if (__builtin_expect(_M_init == false, false)) _M_initialize(); } void _M_destroy() throw(); char* _M_reserve_block(size_t __bytes, const size_t __thread_id); void _M_reclaim_block(char* __p, size_t __bytes) throw (); const _Bin_record& _M_get_bin(size_t __which) { return _M_bin[__which]; } void _M_adjust_freelist(const _Bin_record& __bin, _Block_record* __block, size_t __thread_id) { if (__gthread_active_p()) { __block->_M_thread_id = __thread_id; --__bin._M_free[__thread_id]; ++__bin._M_used[__thread_id]; } } // XXX GLIBCXX_ABI Deprecated _GLIBCXX_CONST void _M_destroy_thread_key(void*) throw (); size_t _M_get_thread_id(); explicit __pool() : _M_bin(NULL), _M_bin_size(1), _M_thread_freelist(NULL) { } explicit __pool(const __pool_base::_Tune& __tune) : __pool_base(__tune), _M_bin(NULL), _M_bin_size(1), _M_thread_freelist(NULL) { } private: // An "array" of bin_records each of which represents a specific // power of 2 size. Memory to this "array" is allocated in // _M_initialize(). _Bin_record* _M_bin; // Actual value calculated in _M_initialize(). size_t _M_bin_size; _Thread_record* _M_thread_freelist; void* _M_thread_freelist_initial; void _M_initialize(); }; #endif template<template <bool> class _PoolTp, bool _Thread> struct __common_pool { typedef _PoolTp<_Thread> pool_type; static pool_type& _S_get_pool() { static pool_type _S_pool; return _S_pool; } }; template<template <bool> class _PoolTp, bool _Thread> struct __common_pool_base; template<template <bool> class _PoolTp> struct __common_pool_base<_PoolTp, false> : public __common_pool<_PoolTp, false> { using __common_pool<_PoolTp, false>::_S_get_pool; static void _S_initialize_once() { static bool __init; if (__builtin_expect(__init == false, false)) { _S_get_pool()._M_initialize_once(); __init = true; } } }; #ifdef __GTHREADS template<template <bool> class _PoolTp> struct __common_pool_base<_PoolTp, true> : public __common_pool<_PoolTp, true> { using __common_pool<_PoolTp, true>::_S_get_pool; static void _S_initialize() { _S_get_pool()._M_initialize_once(); } static void _S_initialize_once() { static bool __init; if (__builtin_expect(__init == false, false)) { if (__gthread_active_p()) { // On some platforms, __gthread_once_t is an aggregate. static __gthread_once_t __once = __GTHREAD_ONCE_INIT; __gthread_once(&__once, _S_initialize); } // Double check initialization. May be necessary on some // systems for proper construction when not compiling with // thread flags. _S_get_pool()._M_initialize_once(); __init = true; } } }; #endif /// Policy for shared __pool objects. template<template <bool> class _PoolTp, bool _Thread> struct __common_pool_policy : public __common_pool_base<_PoolTp, _Thread> { template<typename _Tp1, template <bool> class _PoolTp1 = _PoolTp, bool _Thread1 = _Thread> struct _M_rebind { typedef __common_pool_policy<_PoolTp1, _Thread1> other; }; using __common_pool_base<_PoolTp, _Thread>::_S_get_pool; using __common_pool_base<_PoolTp, _Thread>::_S_initialize_once; }; template<typename _Tp, template <bool> class _PoolTp, bool _Thread> struct __per_type_pool { typedef _Tp value_type; typedef _PoolTp<_Thread> pool_type; static pool_type& _S_get_pool() { // Sane defaults for the _PoolTp. typedef typename pool_type::_Block_record _Block_record; const static size_t __a = (__alignof__(_Tp) >= sizeof(_Block_record) ? __alignof__(_Tp) : sizeof(_Block_record)); typedef typename __pool_base::_Tune _Tune; static _Tune _S_tune(__a, sizeof(_Tp) * 64, sizeof(_Tp) * 2 >= __a ? sizeof(_Tp) * 2 : __a, sizeof(_Tp) * size_t(_Tune::_S_chunk_size), _Tune::_S_max_threads, _Tune::_S_freelist_headroom, std::getenv("GLIBCXX_FORCE_NEW") ? true : false); static pool_type _S_pool(_S_tune); return _S_pool; } }; template<typename _Tp, template <bool> class _PoolTp, bool _Thread> struct __per_type_pool_base; template<typename _Tp, template <bool> class _PoolTp> struct __per_type_pool_base<_Tp, _PoolTp, false> : public __per_type_pool<_Tp, _PoolTp, false> { using __per_type_pool<_Tp, _PoolTp, false>::_S_get_pool; static void _S_initialize_once() { static bool __init; if (__builtin_expect(__init == false, false)) { _S_get_pool()._M_initialize_once(); __init = true; } } }; #ifdef __GTHREADS template<typename _Tp, template <bool> class _PoolTp> struct __per_type_pool_base<_Tp, _PoolTp, true> : public __per_type_pool<_Tp, _PoolTp, true> { using __per_type_pool<_Tp, _PoolTp, true>::_S_get_pool; static void _S_initialize() { _S_get_pool()._M_initialize_once(); } static void _S_initialize_once() { static bool __init; if (__builtin_expect(__init == false, false)) { if (__gthread_active_p()) { // On some platforms, __gthread_once_t is an aggregate. static __gthread_once_t __once = __GTHREAD_ONCE_INIT; __gthread_once(&__once, _S_initialize); } // Double check initialization. May be necessary on some // systems for proper construction when not compiling with // thread flags. _S_get_pool()._M_initialize_once(); __init = true; } } }; #endif /// Policy for individual __pool objects. template<typename _Tp, template <bool> class _PoolTp, bool _Thread> struct __per_type_pool_policy : public __per_type_pool_base<_Tp, _PoolTp, _Thread> { template<typename _Tp1, template <bool> class _PoolTp1 = _PoolTp, bool _Thread1 = _Thread> struct _M_rebind { typedef __per_type_pool_policy<_Tp1, _PoolTp1, _Thread1> other; }; using __per_type_pool_base<_Tp, _PoolTp, _Thread>::_S_get_pool; using __per_type_pool_base<_Tp, _PoolTp, _Thread>::_S_initialize_once; }; /// Base class for _Tp dependent member functions. template<typename _Tp> class __mt_alloc_base { public: typedef size_t size_type; typedef ptrdiff_t difference_type; typedef _Tp* pointer; typedef const _Tp* const_pointer; typedef _Tp& reference; typedef const _Tp& const_reference; typedef _Tp value_type; pointer address(reference __x) const { return &__x; } const_pointer address(const_reference __x) const { return &__x; } size_type max_size() const throw() { return size_t(-1) / sizeof(_Tp); } // _GLIBCXX_RESOLVE_LIB_DEFECTS // 402. wrong new expression in [some_] allocator::construct void construct(pointer __p, const _Tp& __val) { ::new((void *)__p) _Tp(__val); } #ifdef __GXX_EXPERIMENTAL_CXX0X__ template<typename... _Args> void construct(pointer __p, _Args&&... __args) { ::new((void *)__p) _Tp(std::forward<_Args>(__args)...); } #endif void destroy(pointer __p) { __p->~_Tp(); } }; #ifdef __GTHREADS #define __thread_default true #else #define __thread_default false #endif /** * @brief This is a fixed size (power of 2) allocator which - when * compiled with thread support - will maintain one freelist per * size per thread plus a @a global one. Steps are taken to limit * the per thread freelist sizes (by returning excess back to * the @a global list). * @ingroup allocators * * Further details: * http://gcc.gnu.org/onlinedocs/libstdc++/manual/bk01pt12ch32.html */ template<typename _Tp, typename _Poolp = __common_pool_policy<__pool, __thread_default> > class __mt_alloc : public __mt_alloc_base<_Tp> { public: typedef size_t size_type; typedef ptrdiff_t difference_type; typedef _Tp* pointer; typedef const _Tp* const_pointer; typedef _Tp& reference; typedef const _Tp& const_reference; typedef _Tp value_type; typedef _Poolp __policy_type; typedef typename _Poolp::pool_type __pool_type; template<typename _Tp1, typename _Poolp1 = _Poolp> struct rebind { typedef typename _Poolp1::template _M_rebind<_Tp1>::other pol_type; typedef __mt_alloc<_Tp1, pol_type> other; }; __mt_alloc() throw() { } __mt_alloc(const __mt_alloc&) throw() { } template<typename _Tp1, typename _Poolp1> __mt_alloc(const __mt_alloc<_Tp1, _Poolp1>&) throw() { } ~__mt_alloc() throw() { } pointer allocate(size_type __n, const void* = 0); void deallocate(pointer __p, size_type __n); const __pool_base::_Tune _M_get_options() { // Return a copy, not a reference, for external consumption. return __policy_type::_S_get_pool()._M_get_options(); } void _M_set_options(__pool_base::_Tune __t) { __policy_type::_S_get_pool()._M_set_options(__t); } }; template<typename _Tp, typename _Poolp> typename __mt_alloc<_Tp, _Poolp>::pointer __mt_alloc<_Tp, _Poolp>:: allocate(size_type __n, const void*) { if (__n > this->max_size()) std::__throw_bad_alloc(); __policy_type::_S_initialize_once(); // Requests larger than _M_max_bytes are handled by operator // new/delete directly. __pool_type& __pool = __policy_type::_S_get_pool(); const size_t __bytes = __n * sizeof(_Tp); if (__pool._M_check_threshold(__bytes)) { void* __ret = ::operator new(__bytes); return static_cast<_Tp*>(__ret); } // Round up to power of 2 and figure out which bin to use. const size_t __which = __pool._M_get_binmap(__bytes); const size_t __thread_id = __pool._M_get_thread_id(); // Find out if we have blocks on our freelist. If so, go ahead // and use them directly without having to lock anything. char* __c; typedef typename __pool_type::_Bin_record _Bin_record; const _Bin_record& __bin = __pool._M_get_bin(__which); if (__bin._M_first[__thread_id]) { // Already reserved. typedef typename __pool_type::_Block_record _Block_record; _Block_record* __block = __bin._M_first[__thread_id]; __bin._M_first[__thread_id] = __block->_M_next; __pool._M_adjust_freelist(__bin, __block, __thread_id); __c = reinterpret_cast<char*>(__block) + __pool._M_get_align(); } else { // Null, reserve. __c = __pool._M_reserve_block(__bytes, __thread_id); } return static_cast<_Tp*>(static_cast<void*>(__c)); } template<typename _Tp, typename _Poolp> void __mt_alloc<_Tp, _Poolp>:: deallocate(pointer __p, size_type __n) { if (__builtin_expect(__p != 0, true)) { // Requests larger than _M_max_bytes are handled by // operators new/delete directly. __pool_type& __pool = __policy_type::_S_get_pool(); const size_t __bytes = __n * sizeof(_Tp); if (__pool._M_check_threshold(__bytes)) ::operator delete(__p); else __pool._M_reclaim_block(reinterpret_cast<char*>(__p), __bytes); } } template<typename _Tp, typename _Poolp> inline bool operator==(const __mt_alloc<_Tp, _Poolp>&, const __mt_alloc<_Tp, _Poolp>&) { return true; } template<typename _Tp, typename _Poolp> inline bool operator!=(const __mt_alloc<_Tp, _Poolp>&, const __mt_alloc<_Tp, _Poolp>&) { return false; } #undef __thread_default _GLIBCXX_END_NAMESPACE #endif
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