[ On Fri, December 18, 1998 at 09:11:49 (+0200), Lucio de Re wrote: ]
> Subject: Re: userid partitioned swap spaces. 
>
> If one _could_ have something like kibitz reach out and page you, the 
> 400km are no longer a big deal :-)  That is not entirely out of the 
> question, with some careful thinking.

The system should be more robust than relying on an external operator to
intervene in these kinds of situations.

I know that robust programming isn't always the easiest thing to do, but
if the system itself isn't robust then all the programming efforts in
the world of user-land robustness are not going to help!  ;-)

> > But if the killer process does its job well, this is not necessary..
> > 
> I think merely suspending any further process loading until swap space 
> returns below the low-water mark would be less intrusive, but that's 
> merely a policy that can be tuned to local conditions.

Of course merely suspending fork et al would be less intrusive, but
unless you go around knocking on some doors to at least say "We're in
trouble here!  Something's got to be done!" then you can't assume that
the user land will notice anything at all or do anything positive.  You
don't have to have a smoking gun in hand when you knock on those doors,
but sometimes it helps....  (How's that for an analogy that's apropos
for world politics this week!  ;-)

Remember -- the kernel has *already* over-commited VM space.  What else
can it do when suddenly it's in a COW situation with nowhere to copy to?

Right now all it does is "have a cow" and everything usually comes to a
grinding halt.  (For all you non-farmers: cow's are very stubborn *and*
very stupid animals -- you have to be really smart and sneaky to get
them to do what you want without raising a rukus.)  (For all you pedant
etymologists, no, I don't know if that's the true origin of that
phrase.)

-- 
							Greg A. Woods

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