Compelling examples of custom C++ allocators?

c++ memory-management std memory-alignment allocator
Naaff picture Naaff · May 5, 2009 · Viewed 96.4k times · Source

What are some really good reasons to ditch std::allocator in favor of a custom solution? Have you run across any situations where it was absolutely necessary for correctness, performance, scalability, etc? Any really clever examples?

Custom allocators have always been a feature of the Standard Library that I haven't had much need for. I was just wondering if anyone here on SO could provide some compelling examples to justify their existence.

Answer

timday picture timday · May 5, 2009

As I mention here, I've seen Intel TBB's custom STL allocator significantly improve performance of a multithreaded app simply by changing a single 

std::vector<T>

to 

std::vector<T,tbb::scalable_allocator<T> >

(this is a quick and convenient way of switching the allocator to use TBB's nifty thread-private heaps; see page 7 in this document)

Related questions

In what cases do I use malloc and/or new?

I see in C++ there are multiple ways to allocate and free data and I understand that when you call malloc you should call free and when you use the new operator you should pair with delete and it is …

Read More
Does delete on a pointer to a subclass call the base class destructor?

I have an class A which uses a heap memory allocation for one of its fields. Class A is instantiated and stored as a pointer field in another class (class B. When I'm done with an object of class B, …

Read More
Can a local variable's memory be accessed outside its scope?

I have the following code. #include <iostream> int * foo() { int a = 5; return &a; } int main() { int* p = foo(); std::cout << *p; *p = 8; std::cout << *p; } And the code is just running with no …

Read More