When to call SetProcessWorkingSetSize? (Convincing the memory manager to release the memory)

Question

In a previous post ( My program never releases the memory back. Why? ) I show that FastMM can cache (read as hold for itself) pretty large amounts of memory. If your applica

Answer 1

I agree with Lars Truijens 100%, if you don't than you can check the FasttMM memory usage via FasttMM calls GetMemoryManagerState and GetMemoryManagerUsageSummary before and after calling API SetProcessWorkingSetSize.

Answer 2

I used this function just once, when I implemented TWebBrowser. This component took me so much memory even if I destroyed the instance.

Answer 3

Are you sure there is a problem? Working sets might only decrease when there really is a memory shortage.

Answer 4

If SetProcessWorkingSetSize would solve your problem, then your problem is not that FastMM is keeping hold of memory. Since this function will just trim the workingset of your application by writing the memory in RAM to the page file. Nothing is released back to Windows.

In fact you only have made accessing the memory again slower, since it now has to be read from disc. This method has the same effect as minimising your application. Then Windows presumes you are not going to use the application again soon and also writes the workingset in RAM to the pagefile. Windows does a good job of deciding when to write RAM to the pagefile and tries to keep the most used memory in RAM as long as it can. It will make the workinset size smaller (write to pagefile) when there is little RAM left. I would not mess with it just to give the illusion that you program is using less memory while in fact it is using just as much as before, only now it is slower to access. Memory that is accessed again will be loaded into RAM again and make the workinset size grow again. Touching less memory keeps the workingset size smaller.

So no, this will not help you forcing FastMM to release the memory. If your goal is for your application to use less memory you should look elsewhere. Look for leaks, look for heap fragmentations look for optimisations and if you think FastMM is keeping you from doing so you should try to find facts to support it. If your goal is to keep your workinset size small you could try to keep your memory access local. Maybe FastMM or another memory manager could help you with it, but it is a very different problem compared to using to much memory. And maybe this function does help you solve the problem you are having, but I would use it with care and certainly not use it just to keep the illusion that your program has a low memory usage.

Answer 5

Problem solved:
I don't need to use SetProcessWorkingSetSize. FastMM will eventually release the RAM.

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To confirm that this behavior is generated by FastMM (as suggested by Barry Kelly) I crated a second program that allocated A LOT of RAM. As soon as Windows ran out of RAM, my program memory utilization returned to its original value.