Re: [RFC] RSS guarantees and limits

["John Fremlin" <vii@penguinpowered.com>]

Stephen Tweedie <sct@redhat.com> writes:

> On Thu, Jun 22, 2000 at 07:00:54PM +0100, John Fremlin wrote:
> > 
> > > - protect smaller apps from bigger memory hogs
> > 
> > Why? Yes, it's very altruistic, very sportsmanlike, but giving small,
> > rarely used processes a form of social security is only going to
> > increase bureaucracy ;-)
> 
> It is critically important that when under memory pressure, a
> system administrator can still log in and kill any runaway
> processes.  The smaller apps in question here are system daemons
> such as init, inetd and telnetd, and user apps such as bash and
> ps.  We _must_ be able to allow them to make at least some
> progress while the VM is under load.

I agree completely. It was one of the reasons I suggested that a
syscall like nice but giving info to the mm layer would be useful. In
general, small apps (xeyes,biff,gpm) don't deserve any special
treatment.

I also said that on a multiuser system it is important that one user
can't hog the system. In the case where it is impossible for a large
app to drop root privileges being root wouldn't help unless an
exception were made for admin caps.

The only general solution I can see is to give some process (groups) a
higher MM priority, by analogy with nice.

It is critically important that an admin can login to kill a swarm of
tiny runaway processes. A tiny program that forks every few seconds
can bring down a machine just as, if not more effectively than, a
couple of large runaways.

[...]

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