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gcc/libstdc++-v3/include/ext/mt_allocator.h
Brad Spencer 1190bcd85d mt_allocator.h: Handle allocations at static initialization that happen before _S_options is... 
2004-06-30  Brad Spencer  <spencer@infointeractive.com>

	* include/ext/mt_allocator.h: Handle allocations at static
	initialization that happen before _S_options is (automatically)
	constructed; set _S_init even if _M_force_new is true.

From-SVN: r83949
2004-07-01 02:21:51 +00:00

719 lines
23 KiB
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// MT-optimized allocator -*- C++ -*-
// Copyright (C) 2003, 2004 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 2, 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.
// You should have received a copy of the GNU General Public License along
// with this library; see the file COPYING. If not, write to the Free
// Software Foundation, 59 Temple Place - Suite 330, Boston, MA 02111-1307,
// USA.
// As a special exception, you may use this file as part of a free software
// library without restriction. Specifically, if other files instantiate
// templates or use macros or inline functions from this file, or you compile
// this file and link it with other files to produce an executable, this
// file does not by itself cause the resulting executable to be covered by
// the GNU General Public License. This exception does not however
// invalidate any other reasons why the executable file might be covered by
// the GNU General Public License.
/** @file ext/mt_allocator.h
* This file is a GNU extension to the Standard C++ Library.
* You should only include this header if you are using GCC 3 or later.
*/
#ifndef _MT_ALLOCATOR_H
#define _MT_ALLOCATOR_H 1
#include <new>
#include <cstdlib>
#include <bits/functexcept.h>
#include <bits/gthr.h>
#include <bits/atomicity.h>
namespace __gnu_cxx
{
/**
* 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 "global" one. Steps are taken to limit
* the per thread freelist sizes (by returning excess back to
* "global").
*
* Further details:
* http://gcc.gnu.org/onlinedocs/libstdc++/ext/mt_allocator.html
*/
template<typename _Tp>
class __mt_alloc
{
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;
template<typename _Tp1>
struct rebind
{ typedef __mt_alloc<_Tp1> other; };
__mt_alloc() throw()
{
// XXX
}
__mt_alloc(const __mt_alloc&) throw()
{
// XXX
}
template<typename _Tp1>
__mt_alloc(const __mt_alloc<_Tp1>& obj) throw()
{
// XXX
}
~__mt_alloc() throw() { }
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(__p) _Tp(__val); }
void
destroy(pointer __p) { __p->~_Tp(); }
pointer
allocate(size_type __n, const void* = 0);
void
deallocate(pointer __p, size_type __n);
// Variables used to configure the behavior of the allocator,
// assigned and explained in detail below.
struct _Tune
{
// 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.
size_t _M_max_bytes;
// Size in bytes of the smallest bin.
// NB: Must be a power of 2 and >= _M_align.
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 choosen the value below.
// See http://gcc.gnu.org/ml/libstdc++/2001-07/msg00077.html
size_t _M_chunk_size;
// The maximum number of supported threads. Our Linux 2.4.18
// reports 4070 in /proc/sys/kernel/threads-max
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(8), _M_max_bytes(128), _M_min_bin(8),
_M_chunk_size(4096 - 4 * sizeof(void*)),
_M_max_threads(4096), _M_freelist_headroom(10),
_M_force_new(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)
{ }
};
private:
// We need to create the initial lists and set up some variables
// before we can answer to the first request for memory.
#ifdef __GTHREADS
static __gthread_once_t _S_once;
#endif
static bool _S_init;
static void
_S_initialize();
// Configuration options.
static _Tune _S_options;
static const _Tune
_S_get_options()
{ return _S_options; }
static void
_S_set_options(_Tune __t)
{
if (!_S_init)
_S_options = __t;
}
// Using short int as type for the binmap implies we are never
// caching blocks larger than 65535 with this allocator
typedef unsigned short int _Binmap_type;
static _Binmap_type* _S_binmap;
// 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.
#ifdef __GTHREADS
struct _Thread_record
{
// Points to next free thread id record. NULL if last record in list.
_Thread_record* volatile _M_next;
// Thread id ranging from 1 to _S_max_threads.
size_t _M_id;
};
static _Thread_record* volatile _S_thread_freelist_first;
static __gthread_mutex_t _S_thread_freelist_mutex;
static __gthread_key_t _S_thread_key;
static void
_S_destroy_thread_key(void* __freelist_pos);
#endif
static size_t
_S_get_thread_id();
union _Block_record
{
// Points to the block_record of the next free block.
_Block_record* volatile _M_next;
#ifdef __GTHREADS
// The thread id of the thread which has requested this block.
size_t _M_thread_id;
#endif
};
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** volatile _M_first;
#ifdef __GTHREADS
// An "array" of counters used to keep track of the amount of
// blocks that are on the freelist/used for each thread id.
// Memory to these "arrays" is allocated in _S_initialize() for
// _S_max_threads + global pool 0.
size_t* volatile _M_free;
size_t* volatile _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;
#endif
};
// An "array" of bin_records each of which represents a specific
// power of 2 size. Memory to this "array" is allocated in
// _S_initialize().
static _Bin_record* volatile _S_bin;
// Actual value calculated in _S_initialize().
static size_t _S_bin_size;
};
template<typename _Tp>
typename __mt_alloc<_Tp>::pointer
__mt_alloc<_Tp>::
allocate(size_type __n, const void*)
{
// Although the test in __gthread_once() would suffice, we wrap
// test of the once condition in our own unlocked check. This
// saves one function call to pthread_once() (which itself only
// tests for the once value unlocked anyway and immediately
// returns if set)
if (!_S_init)
{
#ifdef __GTHREADS
if (__gthread_active_p())
__gthread_once(&_S_once, _S_initialize);
#endif
if (!_S_init)
_S_initialize();
}
// Requests larger than _M_max_bytes are handled by new/delete
// directly.
const size_t __bytes = __n * sizeof(_Tp);
if (__bytes > _S_options._M_max_bytes || _S_options._M_force_new)
{
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 = _S_binmap[__bytes];
const size_t __thread_id = _S_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.
const _Bin_record& __bin = _S_bin[__which];
_Block_record* __block = NULL;
if (__bin._M_first[__thread_id] == NULL)
{
// NB: For alignment reasons, we can't use the first _M_align
// bytes, even when sizeof(_Block_record) < _M_align.
const size_t __bin_size = ((_S_options._M_min_bin << __which)
+ _S_options._M_align);
size_t __block_count = _S_options._M_chunk_size / __bin_size;
// Are we using threads?
// - Yes, check if there are free blocks on the global
// list. If so, grab up to __block_count blocks in one
// lock and change ownership. If the global list is
// empty, we allocate a new chunk and add those blocks
// directly to our own freelist (with us as owner).
// - No, all operations are made directly to global pool 0
// no need to lock or change ownership but check for free
// blocks on global list (and if not add new ones) and
// get the first one.
#ifdef __GTHREADS
if (__gthread_active_p())
{
__gthread_mutex_lock(__bin._M_mutex);
if (__bin._M_first[0] == NULL)
{
// No need to hold the lock when we are adding a
// whole chunk to our own list.
__gthread_mutex_unlock(__bin._M_mutex);
void* __v = ::operator new(_S_options._M_chunk_size);
__bin._M_first[__thread_id] = static_cast<_Block_record*>(__v);
__bin._M_free[__thread_id] = __block_count;
--__block_count;
__block = __bin._M_first[__thread_id];
while (__block_count-- > 0)
{
char* __c = reinterpret_cast<char*>(__block) + __bin_size;
__block->_M_next = reinterpret_cast<_Block_record*>(__c);
__block = __block->_M_next;
}
__block->_M_next = NULL;
}
else
{
// Is the number of required blocks greater than or
// equal to the number that can be provided by the
// global free list?
__bin._M_first[__thread_id] = __bin._M_first[0];
if (__block_count >= __bin._M_free[0])
{
__bin._M_free[__thread_id] = __bin._M_free[0];
__bin._M_free[0] = 0;
__bin._M_first[0] = NULL;
}
else
{
__bin._M_free[__thread_id] = __block_count;
__bin._M_free[0] -= __block_count;
--__block_count;
__block = __bin._M_first[0];
while (__block_count-- > 0)
__block = __block->_M_next;
__bin._M_first[0] = __block->_M_next;
__block->_M_next = NULL;
}
__gthread_mutex_unlock(__bin._M_mutex);
}
}
else
#endif
{
void* __v = ::operator new(_S_options._M_chunk_size);
__bin._M_first[0] = static_cast<_Block_record*>(__v);
--__block_count;
__block = __bin._M_first[0];
while (__block_count-- > 0)
{
char* __c = reinterpret_cast<char*>(__block) + __bin_size;
__block->_M_next = reinterpret_cast<_Block_record*>(__c);
__block = __block->_M_next;
}
__block->_M_next = NULL;
}
}
__block = __bin._M_first[__thread_id];
__bin._M_first[__thread_id] = __bin._M_first[__thread_id]->_M_next;
#ifdef __GTHREADS
if (__gthread_active_p())
{
__block->_M_thread_id = __thread_id;
--__bin._M_free[__thread_id];
++__bin._M_used[__thread_id];
}
#endif
char* __c = reinterpret_cast<char*>(__block) + _S_options._M_align;
return static_cast<_Tp*>(static_cast<void*>(__c));
}
template<typename _Tp>
void
__mt_alloc<_Tp>::
deallocate(pointer __p, size_type __n)
{
// Requests larger than _M_max_bytes are handled by operators
// new/delete directly.
const size_t __bytes = __n * sizeof(_Tp);
if (__bytes > _S_options._M_max_bytes || _S_options._M_force_new)
{
::operator delete(__p);
return;
}
// Round up to power of 2 and figure out which bin to use.
const size_t __which = _S_binmap[__bytes];
const _Bin_record& __bin = _S_bin[__which];
char* __c = reinterpret_cast<char*>(__p) - _S_options._M_align;
_Block_record* __block = reinterpret_cast<_Block_record*>(__c);
#ifdef __GTHREADS
if (__gthread_active_p())
{
// Calculate the number of records to remove from our freelist:
// in order to avoid too much contention we wait until the
// number of records is "high enough".
const size_t __thread_id = _S_get_thread_id();
long __remove = ((__bin._M_free[__thread_id]
* _S_options._M_freelist_headroom)
- __bin._M_used[__thread_id]);
if (__remove > static_cast<long>(100 * (_S_bin_size - __which)
* _S_options._M_freelist_headroom)
&& __remove > static_cast<long>(__bin._M_free[__thread_id]))
{
_Block_record* __tmp = __bin._M_first[__thread_id];
_Block_record* __first = __tmp;
__remove /= _S_options._M_freelist_headroom;
const long __removed = __remove;
--__remove;
while (__remove-- > 0)
__tmp = __tmp->_M_next;
__bin._M_first[__thread_id] = __tmp->_M_next;
__bin._M_free[__thread_id] -= __removed;
__gthread_mutex_lock(__bin._M_mutex);
__tmp->_M_next = __bin._M_first[0];
__bin._M_first[0] = __first;
__bin._M_free[0] += __removed;
__gthread_mutex_unlock(__bin._M_mutex);
}
// Return this block to our list and update counters and
// owner id as needed.
--__bin._M_used[__block->_M_thread_id];
__block->_M_next = __bin._M_first[__thread_id];
__bin._M_first[__thread_id] = __block;
++__bin._M_free[__thread_id];
}
else
#endif
{
// Single threaded application - return to global pool.
__block->_M_next = __bin._M_first[0];
__bin._M_first[0] = __block;
}
}
template<typename _Tp>
void
__mt_alloc<_Tp>::
_S_initialize()
{
// This method is called on the first allocation (when _S_init is still
// false) to create the bins.
// Ensure that the static initialization of _S_options has
// happened. This depends on (a) _M_align == 0 being an invalid
// value that is only present at startup, and (b) the real
// static initialization that happens later not actually
// changing anything.
if (_S_options._M_align == 0)
new (&_S_options) _Tune;
// _M_force_new must not change after the first allocate(),
// which in turn calls this method, so if it's false, it's false
// forever and we don't need to return here ever again.
if (_S_options._M_force_new)
{
_S_init = true;
return;
}
// Calculate the number of bins required based on _M_max_bytes.
// _S_bin_size is statically-initialized to one.
size_t __bin_size = _S_options._M_min_bin;
while (_S_options._M_max_bytes > __bin_size)
{
__bin_size <<= 1;
++_S_bin_size;
}
// Setup the bin map for quick lookup of the relevant bin.
const size_t __j = (_S_options._M_max_bytes + 1) * sizeof(_Binmap_type);
_S_binmap = static_cast<_Binmap_type*>(::operator new(__j));
_Binmap_type* __bp = _S_binmap;
_Binmap_type __bin_max = _S_options._M_min_bin;
_Binmap_type __bint = 0;
for (_Binmap_type __ct = 0; __ct <= _S_options._M_max_bytes; ++__ct)
{
if (__ct > __bin_max)
{
__bin_max <<= 1;
++__bint;
}
*__bp++ = __bint;
}
// Initialize _S_bin and its members.
void* __v = ::operator new(sizeof(_Bin_record) * _S_bin_size);
_S_bin = static_cast<_Bin_record*>(__v);
// If __gthread_active_p() create and initialize the list of
// free thread ids. Single threaded applications use thread id 0
// directly and have no need for this.
#ifdef __GTHREADS
if (__gthread_active_p())
{
const size_t __k = sizeof(_Thread_record) * _S_options._M_max_threads;
__v = ::operator new(__k);
_S_thread_freelist_first = static_cast<_Thread_record*>(__v);
// NOTE! The first assignable thread id is 1 since the
// global pool uses id 0
size_t __i;
for (__i = 1; __i < _S_options._M_max_threads; ++__i)
{
_Thread_record& __tr = _S_thread_freelist_first[__i - 1];
__tr._M_next = &_S_thread_freelist_first[__i];
__tr._M_id = __i;
}
// Set last record.
_S_thread_freelist_first[__i - 1]._M_next = NULL;
_S_thread_freelist_first[__i - 1]._M_id = __i;
// Make sure this is initialized.
#ifndef __GTHREAD_MUTEX_INIT
__GTHREAD_MUTEX_INIT_FUNCTION(&_S_thread_freelist_mutex);
#endif
// Initialize per thread key to hold pointer to
// _S_thread_freelist.
__gthread_key_create(&_S_thread_key, _S_destroy_thread_key);
const size_t __max_threads = _S_options._M_max_threads + 1;
for (size_t __n = 0; __n < _S_bin_size; ++__n)
{
_Bin_record& __bin = _S_bin[__n];
__v = ::operator new(sizeof(_Block_record*) * __max_threads);
__bin._M_first = static_cast<_Block_record**>(__v);
__v = ::operator new(sizeof(size_t) * __max_threads);
__bin._M_free = static_cast<size_t*>(__v);
__v = ::operator new(sizeof(size_t) * __max_threads);
__bin._M_used = static_cast<size_t*>(__v);
__v = ::operator new(sizeof(__gthread_mutex_t));
__bin._M_mutex = static_cast<__gthread_mutex_t*>(__v);
#ifdef __GTHREAD_MUTEX_INIT
{
// Do not copy a POSIX/gthr mutex once in use.
__gthread_mutex_t __tmp = __GTHREAD_MUTEX_INIT;
*__bin._M_mutex = __tmp;
}
#else
{ __GTHREAD_MUTEX_INIT_FUNCTION(__bin._M_mutex); }
#endif
for (size_t __threadn = 0; __threadn < __max_threads;
++__threadn)
{
__bin._M_first[__threadn] = NULL;
__bin._M_free[__threadn] = 0;
__bin._M_used[__threadn] = 0;
}
}
}
else
#endif
for (size_t __n = 0; __n < _S_bin_size; ++__n)
{
_Bin_record& __bin = _S_bin[__n];
__v = ::operator new(sizeof(_Block_record*));
__bin._M_first = static_cast<_Block_record**>(__v);
__bin._M_first[0] = NULL;
}
_S_init = true;
}
template<typename _Tp>
size_t
__mt_alloc<_Tp>::
_S_get_thread_id()
{
#ifdef __GTHREADS
// If we have thread support and it's active we check the thread
// key value and return its id or if it's not set we take the
// first record from _S_thread_freelist and sets the key and
// returns it's id.
if (__gthread_active_p())
{
_Thread_record* __freelist_pos =
static_cast<_Thread_record*>(__gthread_getspecific(_S_thread_key));
if (__freelist_pos == NULL)
{
// Since _S_options._M_max_threads must be larger than
// the theoretical max number of threads of the OS the
// list can never be empty.
__gthread_mutex_lock(&_S_thread_freelist_mutex);
__freelist_pos = _S_thread_freelist_first;
_S_thread_freelist_first = _S_thread_freelist_first->_M_next;
__gthread_mutex_unlock(&_S_thread_freelist_mutex);
__gthread_setspecific(_S_thread_key,
static_cast<void*>(__freelist_pos));
}
return __freelist_pos->_M_id;
}
#endif
// Otherwise (no thread support or inactive) all requests are
// served from the global pool 0.
return 0;
}
#ifdef __GTHREADS
template<typename _Tp>
void
__mt_alloc<_Tp>::
_S_destroy_thread_key(void* __freelist_pos)
{
// Return this thread id record to front of thread_freelist.
__gthread_mutex_lock(&_S_thread_freelist_mutex);
_Thread_record* __tr = static_cast<_Thread_record*>(__freelist_pos);
__tr->_M_next = _S_thread_freelist_first;
_S_thread_freelist_first = __tr;
__gthread_mutex_unlock(&_S_thread_freelist_mutex);
}
#endif
template<typename _Tp>
inline bool
operator==(const __mt_alloc<_Tp>&, const __mt_alloc<_Tp>&)
{ return true; }
template<typename _Tp>
inline bool
operator!=(const __mt_alloc<_Tp>&, const __mt_alloc<_Tp>&)
{ return false; }
template<typename _Tp>
bool __mt_alloc<_Tp>::_S_init = false;
template<typename _Tp>
typename __mt_alloc<_Tp>::_Tune __mt_alloc<_Tp>::_S_options;
template<typename _Tp>
typename __mt_alloc<_Tp>::_Binmap_type* __mt_alloc<_Tp>::_S_binmap;
template<typename _Tp>
typename __mt_alloc<_Tp>::_Bin_record* volatile __mt_alloc<_Tp>::_S_bin;
template<typename _Tp>
size_t __mt_alloc<_Tp>::_S_bin_size = 1;
// Actual initialization in _S_initialize().
#ifdef __GTHREADS
template<typename _Tp>
__gthread_once_t __mt_alloc<_Tp>::_S_once = __GTHREAD_ONCE_INIT;
template<typename _Tp>
typename __mt_alloc<_Tp>::_Thread_record*
volatile __mt_alloc<_Tp>::_S_thread_freelist_first = NULL;
template<typename _Tp>
__gthread_key_t __mt_alloc<_Tp>::_S_thread_key;
template<typename _Tp>
__gthread_mutex_t
#ifdef __GTHREAD_MUTEX_INIT
__mt_alloc<_Tp>::_S_thread_freelist_mutex = __GTHREAD_MUTEX_INIT;
#else
__mt_alloc<_Tp>::_S_thread_freelist_mutex;
#endif
#endif
} // namespace __gnu_cxx
#endif
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