How much memory can x64 process can take on 4GB RAM

Question

I have a x64 application. It is a bit heavy application (in terms of thread counts, memory needed etc). I'm running this application on a 4GB RAM 64-bit Windows7 Quad core machine. But what i notice is after my application takes around 2.2-2.3 GB Ram it crashes. Is this required behavious? Can 64bit applications at max take only 2.3-2.4 GB RAM from 4GB RAM?

Answer 1

No, check that you don't have any overflows or other bugs first. Even 32-bit applications can address - use more RAM, so it would be ridiculous if it was limited on windows 64-bit.

The remaining memory is free for use, right?

Answer 2

The amount of RAM is of no concern, a process allocates virtual memory. The amount of virtual memory you can allocate in a 64-bit process is only limited by the operating system's ability to provide pages to map the virtual memory to RAM. Which is normally only limited by the largest allowed paging file, assuming you didn't create your own mapping with CreateFileMapping(). It is a system setting, Control Panel + System + Advanced. There's an upper limit as well imposed by the Windows edition, 16 gigabytes for Windows 7 Home Premium, 192 gigabytes for Professional and up.

RAM is only used when your program actually accesses the virtual memory. Which generates a page fault when the memory isn't mapped yet. A 64-bit process typically slows down to a crawl due to these page faults if you allocate and use memory considerably beyond the amount of RAM, well before you consume all available pages.

Since you are considerably South of the typical maximum paging file size, this is surely just another plain old heap corruption bug.

Answer 3

Debug your program. Crashing isn't supposed to happen just because you allocate a lot of memory. The usual suspects: math overflows, memory corruptions, failure to handle errors from memory-allocating routines.