Should I put large arrays on stack or heap?

I'm developing a multi-threaded application in C. I'm currently playing with 40 threads and each uses an array of around 2Mb.

I'm currently allocating this array dynamically, so I do:

char *data = malloc(2097152 * sizeof(char));

These threads are serving requests, so this array is constantly allocated and free'd, each time a new request comes in.

All is working fine, but I'm using valgrind's massif tool and it shows me that I have at times an 80Mb heap. So I'm kind of wondering, will I have heap fragmentation problems? I also allocate smaller chunks of memory on other places of my code.

Also, would I benefit from having an static array? I'm looking of ways to improve my performance and I wonder if this would help. However, I'm afraid of doing that and ending up with a stack overflow. 80Mb in the stack seems too large...

Any advice? I really don't know what size of heap/stack is too big.

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You seem to be heading in this direction anyway, but there are some design patterns that you could be using to assist you in this.

firstly memory pooling http://www.codeproject.com/Articles/27487/Why-to-use-memory-pool-and-how-to-implement-it This can be used to remove the overhead of allocating and de-allocating the memory.

second I am going to assume that you are creating threads as well for the sake of completeness

so thread pooling, if you have a pool of threads that access a pool of memory you should be sorted. http://en.wikipedia.org/wiki/Thread_pool_pattern

Hopefully this gives you some help on ideas on how you can go solve your issue.

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