Hello all, I have some doubt regarding mmap function... As it is a known fact that when a file is mmap'd at that time no physical memory is allocated and when the process tries to accesses the data of mmap'd file at that time "page fault" occurs and then the data is brought from disk to RAM. This is what is called as demand But while reading about mmap I found that call to mmap eventually leads invocation of "do_mmap_pgoff()" which allocates the vma area for the file to be mmap'd . The do_mmap_pgoff() make calls to make_pages_present() which in turn calls get_user_pages().... This get_user_pages() does the page fault and brings the file data from disk to pages in VMA in process address space... So if this is the flow then the file data is already in pages in RAM at the end of mmap function(get_user_pages does that!!).... I am really confused here....what is demand paging then in case of mmap??? Because the file data is already brought in memory during call to mmap.... Please help!!! -Adheer -- Kernelnewbies: Help each other learn about the Linux kernel. Archive: http://mail.nl.linux.org/kernelnewbies/ FAQ: http://kernelnewbies.org/faq/
