Commited memory goes to physical RAM or reserves space in the paging file?
- by Sil
When I do VirtualAlloc with MEM_COMMIT this "Allocates physical storage in memory or in the paging file on disk for the specified reserved memory pages" (quote from MSDN article http://msdn.microsoft.com/en-us/library/aa366887%28VS.85%29.aspx).
All is fine up until now BUT:
the description of Commited Bytes Counter says that "Committed memory is the physical memory which has space reserved on the disk paging file(s)."
I also read "Windows via C/C++ 5th edition" and this book says that commiting memory means reserving space in the page file....
The last two cases don't make sense to me... If you commit memory, doesn't that mean that you commit to physical storage (RAM)? The page file being there for swaping out currently unused pages of memory in case memory gets low.
The book says that when you commit memory you actually reserve space in the paging file. If this were true than that would mean that for a committed page there is space reserved in the paging file and a page frame in physical in memory... So twice as much space is needed ?! Isn't the page file's purpose to make the total physical memory larger than it actually is? If I have a 1G of RAM with a 1G page file = 2G of usable "physical memory"(the book also states this but right after that it says what I discribed at point 2).
What am I missing? Thanks.
