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pool_allocator.h: Convert to a global free-list, as per the original SGI/HP design... 

2004-06-08  Paolo Carlini  <pcarlini@suse.de>

	* include/ext/pool_allocator.h: Convert to a global free-list,
	as per the original SGI/HP design: move the implementation
	details to struct __pool_base, from which __pool_alloc derives.
	* src/allocator.cc: Instantiate __pool_base.

From-SVN: r82794
This commit is contained in:
Paolo Carlini 2004-06-08 22:19:18 +00:00 committed by Paolo Carlini
parent 908d0773f0
commit 5f1a5ede6c
3 changed files with 153 additions and 131 deletions
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7
libstdc++-v3/ChangeLog
View File

@ -1,3 +1,10 @@
2004-06-08 Paolo Carlini <pcarlini@suse.de>
* include/ext/pool_allocator.h: Convert to a global free-list,
as per the original SGI/HP design: move the implementation
details to struct __pool_base, from which __pool_alloc derives.
* src/allocator.cc: Instantiate __pool_base.
2004-06-07 Dhruv Matani <dhruvbird@gmx.net>
Paolo Carlini <pcarlini@suse.de>

275
libstdc++-v3/include/ext/pool_allocator.h
View File

@ -71,11 +71,70 @@ namespace __gnu_cxx
* information that we can return the object to the proper free list
* without permanently losing part of the object.
*
* The template parameter specifies whether more than one thread may use
* this allocator. It is safe to allocate an object from one instance
* of the allocator and deallocate it with another one. This effectively
* transfers its ownership to the second one. This may have undesirable
* effects on reference locality.
*
* @endif
* (See @link Allocators allocators info @endlink for more.)
*/
template<bool __threads>
struct __pool_base
{
enum { _S_align = 8 };
enum { _S_max_bytes = 128 };
enum { _S_freelists = _S_max_bytes / _S_align };
union _Obj
{
union _Obj* _M_free_list_link;
char _M_client_data[1]; // The client sees this.
};
static _Obj* volatile _S_free_list[_S_freelists];
// Chunk allocation state.
static char* _S_start_free;
static char* _S_end_free;
static size_t _S_heap_size;
static _STL_mutex_lock _S_lock;
static _Atomic_word _S_force_new;
static size_t
_S_round_up(size_t __bytes)
{ return ((__bytes + (size_t)_S_align - 1) & ~((size_t)_S_align - 1)); }
static size_t
_S_freelist_index(size_t __bytes)
{ return ((__bytes + (size_t)_S_align - 1) / (size_t)_S_align - 1); }
// Returns an object of size __n, and optionally adds to size __n
// free list.
static void*
_S_refill(size_t __n);
// Allocates a chunk for nobjs of size size. nobjs may be reduced
// if it is inconvenient to allocate the requested number.
static char*
_S_chunk_alloc(size_t __n, int& __nobjs);
// It would be nice to use _STL_auto_lock here. But we need a
// test whether threads are in use.
struct _Lock
{
_Lock() { if (__threads) _S_lock._M_acquire_lock(); }
~_Lock() { if (__threads) _S_lock._M_release_lock(); }
} __attribute__ ((__unused__));
friend struct _Lock;
};
typedef __pool_base<true> __pool_alloc_base;
template<typename _Tp>
class __pool_alloc
class __pool_alloc : private __pool_alloc_base
{
public:
typedef size_t size_type;
@ -123,54 +182,6 @@ namespace __gnu_cxx
void
deallocate(pointer __p, size_type __n);
private:
enum {_S_align = 8};
enum {_S_max_bytes = 128};
enum {_S_freelists = _S_max_bytes / _S_align};
union _Obj
{
union _Obj* _M_free_list_link;
char _M_client_data[1]; // The client sees this.
};
static _Obj* volatile _S_free_list[_S_freelists];
// Chunk allocation state.
static char* _S_start_free;
static char* _S_end_free;
static size_t _S_heap_size;
static _STL_mutex_lock _S_lock;
static _Atomic_word _S_force_new;
static size_t
_S_round_up(size_t __bytes)
{ return ((__bytes + (size_t)_S_align - 1) & ~((size_t)_S_align - 1)); }
static size_t
_S_freelist_index(size_t __bytes)
{ return ((__bytes + (size_t)_S_align - 1)/(size_t)_S_align - 1); }
// Returns an object of size __n, and optionally adds to size __n
// free list.
static void*
_S_refill(size_t __n);
// Allocates a chunk for nobjs of size size. nobjs may be reduced
// if it is inconvenient to allocate the requested number.
static char*
_S_chunk_alloc(size_t __n, int& __nobjs);
// It would be nice to use _STL_auto_lock here. But we need a
// test whether threads are in use.
struct _Lock
{
_Lock() { _S_lock._M_acquire_lock(); }
~_Lock() { _S_lock._M_release_lock(); }
} __attribute__ ((__unused__));
friend struct _Lock;
};
template<typename _Tp>
@ -186,82 +197,83 @@ namespace __gnu_cxx
// Allocate memory in large chunks in order to avoid fragmenting the
// heap too much. Assume that __n is properly aligned. We hold
// the allocation lock.
template<typename _Tp>
template<bool __threads>
char*
__pool_alloc<_Tp>::_S_chunk_alloc(size_t __n, int& __nobjs)
__pool_base<__threads>::_S_chunk_alloc(size_t __n, int& __nobjs)
{
char* __result;
size_t __total_bytes = __n * __nobjs;
size_t __bytes_left = _S_end_free - _S_start_free;
if (__bytes_left >= __total_bytes)
{
__result = _S_start_free;
_S_start_free += __total_bytes;
return __result ;
}
{
__result = _S_start_free;
_S_start_free += __total_bytes;
return __result ;
}
else if (__bytes_left >= __n)
{
__nobjs = (int)(__bytes_left/__n);
__total_bytes = __n * __nobjs;
__result = _S_start_free;
_S_start_free += __total_bytes;
return __result;
}
{
__nobjs = (int)(__bytes_left / __n);
__total_bytes = __n * __nobjs;
__result = _S_start_free;
_S_start_free += __total_bytes;
return __result;
}
else
{
size_t __bytes_to_get =
2 * __total_bytes + _S_round_up(_S_heap_size >> 4);
// Try to make use of the left-over piece.
if (__bytes_left > 0)
{
_Obj* volatile* __free_list =
_S_free_list + _S_freelist_index(__bytes_left);
((_Obj*)(void*)_S_start_free)->_M_free_list_link = *__free_list;
*__free_list = (_Obj*)(void*)_S_start_free;
}
_S_start_free = static_cast<char*>(::operator new(__bytes_to_get));
if (_S_start_free == 0)
{
size_t __i;
_Obj* volatile* __free_list;
_Obj* __p;
// Try to make do with what we have. That can't hurt. We
// do not try smaller requests, since that tends to result
// in disaster on multi-process machines.
__i = __n;
for (; __i <= (size_t) _S_max_bytes; __i += (size_t) _S_align)
{
__free_list = _S_free_list + _S_freelist_index(__i);
__p = *__free_list;
if (__p != 0)
{
*__free_list = __p -> _M_free_list_link;
_S_start_free = (char*)__p;
_S_end_free = _S_start_free + __i;
return _S_chunk_alloc(__n, __nobjs);
// Any leftover piece will eventually make it to the
// right free list.
}
}
_S_end_free = 0; // In case of exception.
_S_start_free = static_cast<char*>(::operator new(__bytes_to_get));
// This should either throw an exception or remedy the situation.
// Thus we assume it succeeded.
}
_S_heap_size += __bytes_to_get;
_S_end_free = _S_start_free + __bytes_to_get;
return _S_chunk_alloc(__n, __nobjs);
}
{
size_t __bytes_to_get = (2 * __total_bytes
+ _S_round_up(_S_heap_size >> 4));
// Try to make use of the left-over piece.
if (__bytes_left > 0)
{
_Obj* volatile* __free_list = (_S_free_list
+ _S_freelist_index(__bytes_left));
((_Obj*)(void*)_S_start_free)->_M_free_list_link = *__free_list;
*__free_list = (_Obj*)(void*)_S_start_free;
}
_S_start_free = static_cast<char*>(::operator new(__bytes_to_get));
if (_S_start_free == 0)
{
size_t __i;
_Obj* volatile* __free_list;
_Obj* __p;
// Try to make do with what we have. That can't hurt. We
// do not try smaller requests, since that tends to result
// in disaster on multi-process machines.
__i = __n;
for (; __i <= (size_t) _S_max_bytes; __i += (size_t) _S_align)
{
__free_list = _S_free_list + _S_freelist_index(__i);
__p = *__free_list;
if (__p != 0)
{
*__free_list = __p -> _M_free_list_link;
_S_start_free = (char*)__p;
_S_end_free = _S_start_free + __i;
return _S_chunk_alloc(__n, __nobjs);
// Any leftover piece will eventually make it to the
// right free list.
}
}
_S_end_free = 0; // In case of exception.
_S_start_free = static_cast<char*>(::operator new(__bytes_to_get));
// This should either throw an exception or remedy the situation.
// Thus we assume it succeeded.
}
_S_heap_size += __bytes_to_get;
_S_end_free = _S_start_free + __bytes_to_get;
return _S_chunk_alloc(__n, __nobjs);
}
}
// Returns an object of size __n, and optionally adds to "size
// __n"'s free list. We assume that __n is properly aligned. We
// hold the allocation lock.
template<typename _Tp>
template<bool __threads>
void*
__pool_alloc<_Tp>::_S_refill(size_t __n)
__pool_base<__threads>::_S_refill(size_t __n)
{
int __nobjs = 20;
char* __chunk = _S_chunk_alloc(__n, __nobjs);
@ -270,18 +282,18 @@ namespace __gnu_cxx
_Obj* __current_obj;
_Obj* __next_obj;
int __i;
if (1 == __nobjs)
return __chunk;
return __chunk;
__free_list = _S_free_list + _S_freelist_index(__n);
// Build free list in chunk.
__result = (_Obj*)(void*)__chunk;
*__free_list = __next_obj = (_Obj*)(void*)(__chunk + __n);
for (__i = 1; ; __i++)
{
{
__current_obj = __next_obj;
__next_obj = (_Obj*)(void*)((char*)__next_obj + __n);
__next_obj = (_Obj*)(void*)((char*)__next_obj + __n);
if (__nobjs - 1 == __i)
{
__current_obj -> _M_free_list_link = 0;
@ -329,7 +341,7 @@ namespace __gnu_cxx
__ret = static_cast<_Tp*>(_S_refill(_S_round_up(__bytes)));
else
{
*__free_list = __result -> _M_free_list_link;
*__free_list = __result->_M_free_list_link;
__ret = reinterpret_cast<_Tp*>(__result);
}
if (__builtin_expect(__ret == 0, 0))
@ -367,25 +379,26 @@ namespace __gnu_cxx
}
}
template<typename _Tp>
typename __pool_alloc<_Tp>::_Obj* volatile
__pool_alloc<_Tp>::_S_free_list[_S_freelists];
template<bool __threads>
typename __pool_base<__threads>::_Obj* volatile
__pool_base<__threads>::_S_free_list[_S_freelists];
template<typename _Tp>
char* __pool_alloc<_Tp>::_S_start_free = 0;
template<bool __threads>
char* __pool_base<__threads>::_S_start_free = 0;
template<typename _Tp>
char* __pool_alloc<_Tp>::_S_end_free = 0;
template<bool __threads>
char* __pool_base<__threads>::_S_end_free = 0;
template<typename _Tp>
size_t __pool_alloc<_Tp>::_S_heap_size = 0;
template<bool __threads>
size_t __pool_base<__threads>::_S_heap_size = 0;
template<typename _Tp>
template<bool __threads>
_STL_mutex_lock
__pool_alloc<_Tp>::_S_lock __STL_MUTEX_INITIALIZER;
__pool_base<__threads>::_S_lock __STL_MUTEX_INITIALIZER;
template<typename _Tp> _Atomic_word
__pool_alloc<_Tp>::_S_force_new = 0;
template<bool __threads>
_Atomic_word
__pool_base<__threads>::_S_force_new = 0;
} // namespace __gnu_cxx
#endif

2
libstdc++-v3/src/allocator.cc
View File

@ -46,4 +46,6 @@ namespace __gnu_cxx
// Static members of __pool_alloc.
template class __pool_alloc<char>;
template class __pool_alloc<wchar_t>;
template class __pool_base<true>;
} // namespace __gnu_cxx