Hi Dieder, Am 04.09.2004 um 03:06 schrieb Dieder Bylsma <applelist@spacemoo.com>: Is there anyway to determine which program/process is paged out to a particular swap file? So why do you need to know where paged out memory pages are located? HTH Mike -- Mike Fischer Softwareentwicklung, EDV-Beratung Schulung, Vertrieb Web: <http://homepage.mac.com/mike_fischer/index.html> Note: I read this list in digest mode! Send me a private copy for faster responses. _______________________________________________ darwin-development mailing list | darwin-development@lists.apple.com Help/Unsubscribe/Archives: http://www.lists.apple.com/mailman/listinfo/darwin-development Do not post admin requests to the list. They will be ignored. Err, I'm not a Darwin expert but AFAIK it doesn't really work that way. The vm system pages out single memory pages (4096 byte blocks of memory) not processes as a whole. So pages from a single process could be paged out to multiple physical swap files. And most likely a process will never be completly paged out. Only the least recently used memory goes to disk when RAM is needed. Also some of the address space of a process may be memory mapped to other files. These parts are usually (but not always) read only and will not be written out to disk. They are simply discarded and reloaded later when needed. And another point to note is that the location of a paged out memory page may change over time. Consider for example the case where 4 swap files of 64MB each are in use. Something happens on the system so that lots of memory gets freed and thus more than 128MB of swap space are left available. dynamic_pager will unregister a swap file in such a case and cause the vm system to empty the file of any in use swap space. Due to the fact that the remaining paged out memory is scattered across all 4 swap files the vm system needs to move pages around in order to empty one swap file so it can be deleted. (This is probably a bit oversimplified. I am guessing that when "relocating" paged out memory the system will probably reload them into RAM and then decide in a separate step that some memory needs to go back out to the swap files. This may or may not be the same pages just loaded from the soon to be obsolete swap file.) This example assumes a non-standard setting for the dynamic pager in Mac OS X 10.3: dynamic_pager -H 33554432 -L 134217728 -S 67108864 -F ${swapDir}/swapfile similar to the settings in 10.2. The standard 10.3 configuration creates swap files with increasing size instead of fixed size as in this example but for demonstration purposes this is easier to handle. Finally note that the paged out memory will probably be completly out of order in the swap files. You'd have a hard time piecing it back together even if you knew where it was located. If it's security you're after then it would be a better idea to prevent critical data to be paged out and erase its (RAM) memory right after use.