How to prevent flushing to disk of a memory map opened on a windows temporary delete-on-close file

Question

UPDATE 2 / TL;DR

Is there some way to prevent dirty pages from a windows temporary delete-on-close file being flushed as a result of cl

Answer 1

If I take it correctly, commenting out Arena2 part of code shall reproduce the issue without the need for second process. I have tried this:

1. I edited base_path as follows for convenience:

   char base_path[MAX_PATH];
   GetTempPathA(MAX_PATH, base_path);
   strcat_s(base_path, MAX_PATH, "page_pool");
   

2. I edited n_pages = 1536 * 128 to bring the used memory to 1.5GB, compared to your ~800mb.
3. I have tested TempFileMapping(false) and TempFileMapping(true), one at a time, for the same results.
4. I have tested with Arena2 commented out and intact, for the same results.
5. I have tested on Win8.1 x64 and Win7 x64, for ±10% same results.
6. In my tests, code runs in 2400ms ±10%, only 500ms ±10% spent on deallocating. That's clearly not enough for a flush of 1.5GB on a low-spinning silent HDDs I have there.

So, the question is, what are you observing? I'd suggest that you:

1. Provide your times for comparison
2. Use a different computer for tests, paying attention to excluding software issues such as "same antivirus"
3. Verify that you're not experiencing a RAM shortage.
4. Use xperf to see what's happening during the freeze.

Update I have tested on yet another Win7 x64, and times are 890ms full, 430ms spent on dealloc. I have looked into your results, and what is VERY suspicious is that almost exactly 4000ms is spent in freeze each time on your machine. That can't be a mere coincidence, I believe. Also, it's rather obvious now the the problem is somehow bound to a specific machine you're using. So my suggestions are:

1. As stated above, test on another computer yourself
2. As stated above, Use XPerf, it will allow you to see what exactly happens in user mode and kernel mode during the freeze (I really suspect some non-standard driver in the middle)
3. Play with number of pages and see how it affects the freeze length.
4. Try to store files on a different disk drive on the same computer where you have tested initially.