[ILUG] "Swap-in" tool?

[Niall O Broin]

On Tue, Oct 01, 2002 at 09:50:17AM +0100, Kenn Humborg wrote:

> > swapped but rather paged, hence they don't get put into swap ? I'm not
> > familiar enough with how Linux handles paging/swapping to know
> > what it does
> > in that area.
> 
> Yes.  Unmodified code pages are backed by the executable file itself.
> They never find their way to swap.  All modern OSes that I've looked
> at (Linux, NT, VMS) do this.

OK - I've an idea this could be different in earlier Unices (via the sticky
bit) but that behaviour seems more sensible.

> 
> > > And ptrace() lets me be selective about which processes I want
> > to be resident.
> > > No need to page in a bunch of mingettys!
> >
> > Well, yes, but really, are you going to bother ? When something
> > as simple as
> >
> > for pid = 2 to PID_MAX
> >     word = 0
> >     while not errno
>       ^^^^^^^^^^^^^^^
> 
> Probably won't work because virtual address space is not contiguous.
> I'll need to look at /proc/PID/maps to get the list of valid regions.

Well you live and learn. Not something I've ever looked at before (it's been
a LONG time since I programmed in anything which specified numeric
addresses) but I sort of assumed that a programs VM would just be addressed
from 0-end, with the mapping to real addresses handled by the processor. A
little though about the return value of a malloc of course would have made
it obvious that this isn't true. And then a quick cat of
/proc/somerandompid/maps made me think that there's very little wrong with
the swap frobbing idea :-)



Niall  "If TMTOWTDI I'll take the easier(st) one thanks"  O Broin