Re: running of out memory => kernel crash

[Chris Friesen]

On 08/19/2011 01:29 PM, Bryan Donlan wrote:
> On Thu, Aug 18, 2011 at 10:26, Pavel Ivanov<paivanof@xxxxxxxxx>  wrote:

> > Could you elaborate on this? We have a completely unusable server
> > which can be revived only by hard power cycling (administrators won't
> > be able to log in because sshd and shell will fall victims of the same
> > unending disk reading). And as an alternative we can kill some process
> > and at least allow administrator to log in and check if something else
> > can be done to make server feel better. Why is it worse?
> >
> > I understand that it could be very hard to detect such situation but
> > at least it's worth trying I think.
>
> Deciding when to call the server unusable is a policy decision that
> the kernel can't make very easily on its own; the point when the
> system is considered unusable may be different depending on workload.
> You could create a userspace daemon, however, that mlockall()s, then
> monitors memory usage, load average, etc and kills processes when
> things start to go south. You could also use the memory resource
> cgroup controller to set hard limits on memory usage.

Indeed.  From the point of view of the OS, it's running everything on 
the system without a problem.  It's deep into swap, but it's running.

If there are application requirements on grade-of-service, it's up to 
the application to check whether those are being met and if not to do 
something about it.

Chris

--
Chris Friesen
Software Developer
GENBAND
chris.friesen@xxxxxxxxxxx
www.genband.com
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/