How is it that a write (man 2 write) can be passed a buffer that exceeds most of the physical and virtual memory on a system and work successfully? I wrote a simple program that allocates a large buffer on the heap, zeros the space and then calls write (man 2 write). Even though the buffer is almost as large as physical memory + page space the call completes without error. In my example I allocated 705MB on a system that has 256MB physical and 512MB virtual. When it completes there is a 705MB file on disk as expected. So is it in the case of the sys_write that the memory is accessed and allowed to page fault as needed while running in the context of the kernel? Most of the kernel books talk about using copy_from_user on system calls before using memory from the user. Strace shows one write call with the entire length. So what is going on to allow this to happen? Thanks, Tony -- Kernelnewbies: Help each other learn about the Linux kernel. Archive: http://mail.nl.linux.org/kernelnewbies/ FAQ: http://kernelnewbies.org/faq/
