Robert Elz wrote:
> 
>     Date:        Tue, 13 Jul 1999 14:14:52 -0700 (PDT)
>     From:        Matthew Dillon <dillon@apollo.backplane.com>
>     Message-ID:  <199907132114.OAA80781@apollo.backplane.com>
> 
>   |     If you don't have the disk necessary for a standard overcommit model to
>   |     work, you definitely do not have the disk necessary for a non-overcommit
>   |     model to work.
> 
> This is based upon your somewhat strange definition of "work".   I assure
> you that I have run many systems which don't use overcommit, and which I
> quite frequently run into "out of VM" conditions, and which I can assure
> you, work just fine.   When they're getting to run out of VM, the system
> is approaching paging death, which is as you'd expect (they're overloaded).
> That is, adding more VM (more swap space) would be counterproductive.

Would you care to name such systems? And, btw, a system consuming
all memory is *not* necessarily approaching paging death. More
likely, it is just storing a lot of data in the swap which will
never be used (which is the whole point of overcommit in first
place), and, thus, never paged in.

> I have no doubt but that you can dream up scenarios where you pander to
> the laziness of programmers, and make using huge VM space with little
> of it actually allocated anywhere (or ever touched) then you would indeed
> need monstrous amounts of paging space, most of which is never actually
> used for anything - personally I prefer to have the programmers think
> a little more about the memory footprint of their data structures.  Not
> only does this reduce the VM footprint, it will also usually vastly
> improving the paging characteristics.   Most applications which simply
> scatter data through a huge VM space simply stop being useable as soon
> as their RSS exceeds available physical memory - that is, if they start
> paging, they die (become comatose might be a better description).
> A little intelligent though as to how to actually make use of the mem
> resources can make a huge difference.

Fine. Stay with the allocation of swap for DATA/BSS of each instance
of the same program you are running. That alone is enough.

--
Daniel C. Sobral			(8-DCS)
dcs@newsguy.com
dcs@freebsd.org

	"Would you like to go out with me?"
	"I'd love to."
	"Oh, well, n... err... would you?... ahh... huh... what do I do
next?"