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Quick_allocator updates.

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[SVN r17267]
This commit is contained in:
Peter Dimov
2003-02-07 15:08:52 +00:00
parent 9b9cad3f5b
commit a11ab16010
1 changed files with 52 additions and 22 deletions
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74
include/boost/detail/quick_allocator.hpp
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@ -23,7 +23,6 @@
#include <boost/type_traits/type_with_alignment.hpp>
#include <boost/type_traits/alignment_of.hpp>
#include <deque>
#include <new> // ::operator new, ::operator delete
#include <cstddef> // std::size_t
@ -45,10 +44,27 @@ template<unsigned size, unsigned align> struct allocator_impl
{
typedef freeblock<size, align> block;
// It may seem odd to use such small pages.
//
// However, on a typical Windows implementation that uses
// the OS allocator, "normal size" pages interact with the
// "ordinary" operator new, slowing it down dramatically.
//
// 512 byte pages are handled by the small object allocator,
// and don't interfere with ::new.
//
// The other alternative is to use much bigger pages (1M.)
enum { items_per_page = 496 / size }; // 1048560 / size
#ifdef BOOST_HAS_THREADS
static lightweight_mutex mutex;
static std::deque<block> store;
#endif
static block * free;
static block * page;
static unsigned last;
static inline void * alloc()
{
#ifdef BOOST_HAS_THREADS
@ -61,8 +77,15 @@ template<unsigned size, unsigned align> struct allocator_impl
}
else
{
store.resize(store.size() + 1);
return &store.back();
if(last == items_per_page)
{
// "Listen to me carefully: there is no memory leak"
// -- Scott Meyers, Eff C++ 2nd Ed Item 10
page = ::new block[items_per_page];
last = 0;
}
return &page[last++];
}
}
@ -84,8 +107,13 @@ template<unsigned size, unsigned align> struct allocator_impl
}
else
{
store.resize(store.size() + 1);
return &store.back();
if(last == items_per_page)
{
page = ::new block[items_per_page];
last = 0;
}
return &page[last++];
}
}
}
@ -105,34 +133,36 @@ template<unsigned size, unsigned align> struct allocator_impl
static inline void dealloc(void * pv, std::size_t n)
{
if(pv != 0) // 18.4.1.1/13
if(n != size) // class-specific delete called for a derived object
{
::operator delete(pv);
}
else if(pv != 0) // 18.4.1.1/13
{
if(n != size) // class-specific delete called for a derived object
{
::operator delete(pv);
}
else
{
#ifdef BOOST_HAS_THREADS
lightweight_mutex::scoped_lock lock(mutex);
lightweight_mutex::scoped_lock lock(mutex);
#endif
block * pb = static_cast<block *>(pv);
pb->next = free;
free = pb;
}
block * pb = static_cast<block *>(pv);
pb->next = free;
free = pb;
}
}
};
#ifdef BOOST_HAS_THREADS
template<unsigned size, unsigned align>
lightweight_mutex allocator_impl<size, align>::mutex;
template<unsigned size, unsigned align>
std::deque< freeblock<size, align> > allocator_impl<size, align>::store;
#endif
template<unsigned size, unsigned align>
freeblock<size, align> * allocator_impl<size, align>::free = 0;
template<unsigned size, unsigned align>
freeblock<size, align> * allocator_impl<size, align>::page = 0;
template<unsigned size, unsigned align>
unsigned allocator_impl<size, align>::last = allocator_impl<size, align>::items_per_page;
template<class T>
struct quick_allocator: public allocator_impl< sizeof(T), boost::alignment_of<T>::value >
{