-----BEGIN PGP SIGNED MESSAGE----- Hash: SHA1 On 01/23/08 18:37, Rick Thomas wrote: > > On Jan 23, 2008, at 4:27 PM, David Brodbeck wrote: > >> >> On Jan 22, 2008, at 8:54 PM, Rick Thomas wrote: >> >>> The rule of thumb comes from UNIX days (BSD and even before that with >>> AT&T UNIX). In order to be completely sure you would be able to swap >>> out a program when memory became full, UNIX allocated a page of swap >>> for every page of virtual memory a program occupied. So if vi >>> required 256K to run, there was 256K of swap space allocated to it. >>> The 2 to 1 ratio came from the observation that a busy UNIX >>> time-sharing system with lots of users ran most of it's time with >>> half the users doing something that required CPU/memory resources and >>> the other half thinking, so you could afford to overcommit memory by >>> a factor of two. >> >> Thanks for the interesting history lesson. :) > > You're welcome. It had the interesting side-effect that people > developed the habit, after they were done thinking and wanted to start > working on the computer again, of hitting the <return> key to "wake up > the computer" (really, to initiate a bunch of swap-in operations) then > wait several seconds for the cursor to actually return and the command > prompt to re-appear. The swapping algorithms knew about this behavior > and optimized for it. When a process group had been idle long enough to > indicate the start of a "think" cycle, the whole process group was > swapped out at once. When the user started up again, the whole process > group was swapped in -- assuming that the user would be needing it soon. > > I'm really gettin' old!
Have you yet bitched and complained how kids today have it so much easier, and don't appreciate what they have? - -- Ron Johnson, Jr. Jefferson LA USA "I'm not a vegetarian because I love animals, I'm a vegetarian because I hate vegetables!" unknown -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.4.6 (GNU/Linux) iD8DBQFHl+c+S9HxQb37XmcRAvYKAJ9yvyrbU9IxaJuPiW6kkvGAh/7eMACghnCU cZkvN80s31On0EtjWDGPhzc= =Bu8d -----END PGP SIGNATURE----- -- To UNSUBSCRIBE, email to [EMAIL PROTECTED] with a subject of "unsubscribe". Trouble? Contact [EMAIL PROTECTED]
