Memory fragmentation C++

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Hi!

I and some good friends of mine decided to try making a smaller game in C++ just for fun, with help of DirectX and some other libraries original written in C++. I would say all of us have experience from earlier development projects but however almost only from managed languages. I have been programming in C++ before but never any bigger projects or solutions.

When we did a bit of research we found that it seems like a lot of people worries about memory fragmentation on the heap when creating small short lived objects frequently or when the memory usage grows. We got a bit concerned that we may have to take this under consideration when designing the game engine, instead of just creating objects the C# or Java way with "new". (I'm aware of that you must free the memory unlike in the managed languages mentioned)

Is this something you should worry about and if so what are our options? I have read a bit about memory pools, but will we need one and is there any known already working we could use if so? We are very thankful for all feedback we get on this.

Best Regards
WaZoX

Posted 17-Dec-12 5:49am

WaZoX

Updated 17-Dec-12 8:04am

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3 solutions

Solution 2

A nice "epiphany" about advanced memory management :) :
16 used from $0.01[^]

Posted 17-Dec-12 9:14am

Eugen Podsypalnikov

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Espen Harlinn · Accepted Answer · 2012-12-17T06:21:00

Solution 1

I and some good friends of mine decided to try making a smaller game in C++ just for fun Great :-D

a lot of people worries about memory fragmentation
Many spend time worrying on things that eventually turn out not to be a problem ...

Is this something you should worry about
Probably not, but creating pools of same/similar sized objects can enhance the performance of your program - that's probably a better reason for using memory pools than fragmentation.

C# or Java way with "new". Just remember to delete those objects, or take a look at std::make_shared<> & std::shared_ptr<>

Regards
Espen Harlinn

Posted 17-Dec-12 6:21am

Espen Harlinn

Comments

CPallini 17-Dec-12 12:26pm

5.

Espen Harlinn 17-Dec-12 12:28pm

Thank you, Carlo :-D

WaZoX 17-Dec-12 13:51pm

Thank you very much for your input, sounds great that it doesn't seems to be such a big problem with fragmentation. Means more time for the game! Do you believe memory fragmentation would be a problem for bigger titles like AAA games? I'm aware of the delete keyword but thank you anyway :)

Espen Harlinn 17-Dec-12 15:29pm

I expect they do, but then they have the manpower and budget to do so.

I think you'll find that they are way more concerned over how they manage memory on the graphics card and scheduling of the "events" that drives the game - think orchestration ...

Nelek 17-Dec-12 18:17pm

Nice points. +5

Espen Harlinn 17-Dec-12 19:34pm

Thank you, Nelek :-D

Sergey Alexandrovich Kryukov 29-Dec-12 21:01pm

Nice, a 5.
—SA

Espen Harlinn 30-Dec-12 5:22am

Thank you, Sergey :-D

Philippe Mori · Accepted Answer · 2012-12-18T14:45:00

In practice memory fragmentation could be a problem if you have a lot of objects of varying sizes.

If almost all your objects are relatively small, fragmentation should not be a problem.

On the other hand, if you uses a lot of large std::vector without reserveing memory, you will be prone to memory fragmentation because each time a reallocation occurs, the previously used memory would not be usable for another very large object.

If small and large objects allocations are a lot intermixed, the the problem can be worst.

It also depends a lot on how much memory you use. Given that nowaday machine have gigabytes of RAM, it is less aq problem that it used to be.

Also, you have to be sure that your application does not have memory leak as otherwise available memory will diminish as time goes.