On Tue, 13 Jul 1999, Daniel C. Sobral wrote: > Jon Ribbens wrote: > > > > "Daniel C. Sobral" <d...@newsguy.com> wrote: > > > That's *not* abomination. How about pre-allocating over 100 Mb for X > > > Free, for instance? > > > > What about it? If an application does not need 100MB, it should not > > malloc it. If it does need it, it should malloc it and know that it > > is available if the malloc succeeds. > > Well, learn something about real programs first, and then come back. > > > > Basically, if you don't have enough memory, you just don't have enough > > > memory. > > > > Yes, and the application should be told this via the standard > > documented interface for doing so, i.e. returning NULL from > > malloc(). > > This results in the applications working with less memory than would > actually be possible through overcommit. > > > > What FreeBSD does *reduces* the need for memory. If FreeBSD *did > > > not* do it, then you'd need much more memory. > > > > Why? Are there really such a lot of applications allocating vastly > > more memory than they actually use? > > Right. >
You're not really being fair by giving such simple answers, not that it hasn't been discussed TO DEATH already so i understand your indifference. :) I didn't understand the reasoning of over commit until I was pointed out this scenario: (let's use netscape because it is huge) You're browsing with netscape and It hits about 32megs in size, you click on a multimedia object and netscape execs a helper app. at the moment of the fork you have a major overcommit, considering private mappings and allocated memory that is suddenly doubled when under a second later you will exec a program that is only a meg or so. you also have to consider a program wishing to make sparse use of its address space, without overcommit it becomes impossible. if you want to impose limits, use /etc/login.conf, nuff said. -Alfred Perlstein - [bri...@rush.net|bri...@wintelcom.net] systems administrator and programmer Win Telecom - http://www.wintelcom.net/ To Unsubscribe: send mail to majord...@freebsd.org with "unsubscribe freebsd-hackers" in the body of the message