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Re: patch: mt_allocator.h
Dhruv Matani wrote:
Before any other consideration: is this regtested?
It originally wasn't, but after running it, the patch did pass the
tests, so it's ok ;-)
Ok, thanks. Check-performance too?
I agree with you that, at least, this is the original SGI/HP design
for pool_allocator: see the attached patch, which I will commit soon
to mainline (if nobody object, indeed).
About mt_allocator, I'd like to think about it a little bit more: I'm
not 1000% sure that this is always the best choice also in presence of
threads, and so on.
In any case, what about not splitting mt_allocator in a __gnu_internal::
part and a std:: part? Can't we put *all* the implementation details
inside _Mt_alloc_base?
Paolo.
///////////////
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 static members.
diff -prN libstdc++-v3-orig/include/ext/pool_allocator.h libstdc++-v3/include/ext/pool_allocator.h
*** libstdc++-v3-orig/include/ext/pool_allocator.h Mon Mar 22 14:07:12 2004
--- libstdc++-v3/include/ext/pool_allocator.h Tue Jun 8 15:10:21 2004
*************** namespace __gnu_cxx
*** 74,82 ****
* @endif
* (See @link Allocators allocators info @endlink for more.)
*/
template<typename _Tp>
! class __pool_alloc
{
public:
typedef size_t size_type;
typedef ptrdiff_t difference_type;
--- 74,145 ----
* @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 : private __pool_alloc_base
{
+ typedef __pool_alloc_base::_Obj _Obj;
+ typedef __pool_alloc_base::_Lock _Lock;
+
+ using __pool_alloc_base::_S_force_new;
+ using __pool_alloc_base::_S_max_bytes;
+ using __pool_alloc_base::_S_free_list;
+ using __pool_alloc_base::_S_freelist_index;
+ using __pool_alloc_base::_S_refill;
+
public:
typedef size_t size_type;
typedef ptrdiff_t difference_type;
*************** namespace __gnu_cxx
*** 123,176 ****
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>
--- 186,191 ----
*************** namespace __gnu_cxx
*** 186,267 ****
// 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>
char*
! __pool_alloc<_Tp>::_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 ;
! }
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;
! }
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);
! }
}
!
// 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>
void*
! __pool_alloc<_Tp>::_S_refill(size_t __n)
{
int __nobjs = 20;
char* __chunk = _S_chunk_alloc(__n, __nobjs);
--- 201,283 ----
// 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<bool __threads>
char*
! __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 ;
! }
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;
! }
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);
! }
}
!
// 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<bool __threads>
void*
! __pool_base<__threads>::_S_refill(size_t __n)
{
int __nobjs = 20;
char* __chunk = _S_chunk_alloc(__n, __nobjs);
*************** namespace __gnu_cxx
*** 270,287 ****
_Obj* __current_obj;
_Obj* __next_obj;
int __i;
!
if (1 == __nobjs)
! 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);
if (__nobjs - 1 == __i)
{
__current_obj -> _M_free_list_link = 0;
--- 286,303 ----
_Obj* __current_obj;
_Obj* __next_obj;
int __i;
!
if (1 == __nobjs)
! 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);
if (__nobjs - 1 == __i)
{
__current_obj -> _M_free_list_link = 0;
*************** namespace __gnu_cxx
*** 329,335 ****
__ret = static_cast<_Tp*>(_S_refill(_S_round_up(__bytes)));
else
{
! *__free_list = __result -> _M_free_list_link;
__ret = reinterpret_cast<_Tp*>(__result);
}
if (__builtin_expect(__ret == 0, 0))
--- 345,351 ----
__ret = static_cast<_Tp*>(_S_refill(_S_round_up(__bytes)));
else
{
! *__free_list = __result->_M_free_list_link;
__ret = reinterpret_cast<_Tp*>(__result);
}
if (__builtin_expect(__ret == 0, 0))
*************** namespace __gnu_cxx
*** 367,391 ****
}
}
! template<typename _Tp>
! typename __pool_alloc<_Tp>::_Obj* volatile
! __pool_alloc<_Tp>::_S_free_list[_S_freelists];
! template<typename _Tp>
! char* __pool_alloc<_Tp>::_S_start_free = 0;
! template<typename _Tp>
! char* __pool_alloc<_Tp>::_S_end_free = 0;
! template<typename _Tp>
! size_t __pool_alloc<_Tp>::_S_heap_size = 0;
! template<typename _Tp>
_STL_mutex_lock
! __pool_alloc<_Tp>::_S_lock __STL_MUTEX_INITIALIZER;
! template<typename _Tp> _Atomic_word
! __pool_alloc<_Tp>::_S_force_new = 0;
} // namespace __gnu_cxx
#endif
--- 383,408 ----
}
}
! template<bool __threads>
! typename __pool_base<__threads>::_Obj* volatile
! __pool_base<__threads>::_S_free_list[_S_freelists];
! template<bool __threads>
! char* __pool_base<__threads>::_S_start_free = 0;
! template<bool __threads>
! char* __pool_base<__threads>::_S_end_free = 0;
! template<bool __threads>
! size_t __pool_base<__threads>::_S_heap_size = 0;
! template<bool __threads>
_STL_mutex_lock
! __pool_base<__threads>::_S_lock __STL_MUTEX_INITIALIZER;
! template<bool __threads>
! _Atomic_word
! __pool_base<__threads>::_S_force_new = 0;
} // namespace __gnu_cxx
#endif
diff -prN libstdc++-v3-orig/src/allocator.cc libstdc++-v3/src/allocator.cc
*** libstdc++-v3-orig/src/allocator.cc Mon Mar 22 14:07:12 2004
--- libstdc++-v3/src/allocator.cc Tue Jun 8 15:15:44 2004
*************** namespace __gnu_cxx
*** 46,49 ****
--- 46,60 ----
// Static members of __pool_alloc.
template class __pool_alloc<char>;
template class __pool_alloc<wchar_t>;
+
+ template void* __pool_base<true>::_S_refill(size_t);
+ template char* __pool_base<true>::_S_chunk_alloc(size_t, int&);
+ template
+ __pool_base<true>::_Obj* volatile
+ __pool_base<true>::_S_free_list[_S_freelists];
+ template char* __pool_base<true>::_S_start_free;
+ template char* __pool_base<true>::_S_end_free;
+ template size_t __pool_base<true>::_S_heap_size;
+ template _STL_mutex_lock __pool_base<true>::_S_lock;
+ template _Atomic_word __pool_base<true>::_S_force_new;
} // namespace __gnu_cxx