Object creation in boost::singleton_pool

Question

I am trying to use boost::singleton_pool to create a large number of objects of a type 'Order' in a highly performance critical multithreaded application. Looking at the documentation, this is what I should be doing,

struct OrderTag{};
typedef boost::singleton_pool<OrderTag, sizeof(Order)> OrderPool; 

boost::singleton_pool has a static member function malloc which returns pointer of the void*, but I need to create objects of the type Order in OrderPool by making calls to its constructor. Shall I be using boost::pool_allocator along with singleton_pool to do so?

Thanks.

Answer 1

You can use singleton_pool with placement new like this:

Order* p = new (OrderPool.malloc()) Order(/* add ctor parameters if any*/);

or use boost::object_pool<Order>

Answer 2

In short: no. boost::pool_allocator implementation itself uses boost::singleton_pool and provides interface like std::allocator so you can use it with STL containers (but not only STL and not only containers) like vector, list etc. The UserAllocator concept is not something like boost::pool_allocator but it's a thing that controls memory management at the lowest level. For example I wrote UserAllocator that allocates memory via mmap() function and not uses heap at all.

So to create objects of a type 'Order' you should use boost::pool_allocator or boost::fast_pool_allocator. In your case it is not necessary to use boost::singleton_pool directly.