Windows Memory Mapped Files

Question

I am trying to investigate the behaviour of the Windows Kernel with respect to Memory Mapped Files / Virtual Memory. Specifically I am interested in determining how frequently the contents of a memory mapped file are flushed (by Windows) to disk and what criterion Windows uses for deciding it is time to do so.

I have done a bit of research online and, apart from the MSDN which deals more with the 'hows and whys' rather than detailing the internal workings, there doesn't appear to be much information. If anyone can point me to any articles or has looked into this before and has some insight I would welcome it.

Thanks.

Answer 1

I suggest reading Microsoft Windows Internals by Mark Russinovich and David Solomon, in fifth edition also with Alex Ionescu.

Answer 2

Memory mapped files are controlled by the modified page writer in the kernel - they're flushed whenever the memory that backs the page needs to be re-used (so it can happen under memory pressure).

The system also keeps track of the number of dirty pages and writes them after a threshold is reached.

You can find more information about in this article about Windows memory management changes for Windows Vista - it doesn't directly answer your question about how the memory manager treats modified pages but you can infer some of the details based on the information in the article.