Re: [ANNOUNCE] Minneapolis Cluster Summit, July 29-30

Nick Piggin
2004-07-12T13:40:46Z

Lars Marowsky-Bree wrote:
> On 2004-07-12T14:01:27,
> Arjan van de Ven <arjanv@redhat.com> said:
>
>
>>I'm not convinced that's a good idea, in that it exposes what is
>>basically VM internals to userspace, which then would become a
>>set-in-stone interface....
>
>
> But I'm also not a big fan of moving all HA relevant infrastructure into
> the kernel. Membership and DLM are the first ones; then follows
> messaging (and reliable and globally ordered messaging is somewhat
> complex - but if one node is slow, it will hurt global communication
> too, so...), next someone argues that a node always must be able to
> report which resources it holds and fence other nodes even under memory
> pressure, and there goes the cluster resource manager and fencing
> subsystem into the kernel too etc...
>
> Where's the border?
>
> And what can we do to make critical user-space infrastructure run
> reliably and with deterministic-enough & low latency instead of moving
> it all into the kernel?
>
> Yes, the kernel solves these problems right now, but is that really the
> path we want to head down? Maybe it is, I'm not sure, afterall we also
> have the entire regular network stack in the kernel, but maybe also it
> is not.
>

I don't see why it would be a problem to implement a "this task
facilitates page reclaim" flag for userspace tasks that would take
care of this as well as the kernel does.

There would probably be a few technical things to work out (like
GFP_NOFS), but I think it would be pretty trivial to implement.