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

From: Nick Piggin (nickpiggin_at_yahoo.com.au)
Date: 07/12/04

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    Date:	Mon, 12 Jul 2004 23:40:34 +1000
To: Lars Marowsky-Bree <lmb@suse.de>

    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.
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