On Tue, 2009-10-06 at 18:46 +0200, Andi Kleen wrote:
> On Tue, Oct 06, 2009 at 12:28:49PM -0400, Lee Schermerhorn wrote:
> > On Tue, 2009-10-06 at 18:01 +0200, Andi Kleen wrote:
> > > On Mon, Oct 05, 2009 at 11:19:24PM -0400, Lee Schermerhorn wrote:
> > > > [PATCH 11/11] hugetlb: offload [un]registration of sysfs attr to worker thread
> > > >
> > > > Against: 2.6.31-mmotm-090925-1435
> > > >
> > > > New in V6
> > > >
> > > > V7: + remove redundant check for memory{ful|less} node from
> > > > node_hugetlb_work(). Rely on [added] return from
> > > > hugetlb_register_node() to differentiate between transitions
> > > > to/from memoryless state.
> > > >
> > > > This patch offloads the registration and unregistration of per node
> > > > hstate sysfs attributes to a worker thread rather than attempt the
> > > > allocation/attachment or detachment/freeing of the attributes in
> > > > the context of the memory hotplug handler.
> > >
> > > Why this change? The hotplug handler should be allowed to sleep, shouldn't it?
> >
> > Andy: perhaps it can. I'm not familiar with hotplug, so I followed a
> > pattern found elsewhere. I created a separate patch in case someone
> > familiar with this area says I don't need it.
>
> At least ACPI already puts it on a work queue.
Well, maybe we don't need it then.
>
> > >
> > > > N.B., Only tested build, boot, libhugetlbfs regression.
> > > > i.e., no memory hotplug testing.
> > >
> > > Yes, you have to because I know for a fact it's broken (outside your code) :)
> >
> > We need to be able to remove all memory from a node without that node
> > disappearing [as I think it does on x86_64] to even exercise this code.
>
> Are you sure? x86-64 doesn't support full node hotplug afaik.
I'll have to look. At boot time on x86, we hide any memoryless nodes by
assigning their cpus to other nodes [currently just "round robin", but I
think this needs to change to distance based]. I recall seeing a memory
hotplug handler that moves the cpus when a node becomes memoryless. If
it then unregisters the node [again, have to look. no time now :(], the
earlier patches handle [un]registration of the per node attributes. The
subject code only gets triggered if we have a node that becomes
memoryless as a result of hot remove but remains registered or that
starts memoryless and has memory hot-added.
>
> > I think some ia64 platforms can do that, perhaps others.
>
> I've been thinking about adding a hotadd regression test at boot time that
> only adds memory to nodes later after boot. That would at least test hotadd
> (and hot-removal is dubious anyways).
>
> That wouldn't be real node hotadd, but at least memory hotadd of all
> to a node (which doesn't work currently)
That would be useful for testing the last 3 patches in the series, if
memoryless nodes can exist. Otherwise, the per node attributes will
just come and go with the node itself.
>
> -Andi
>
> P.S.: You can add Reviewed-by for me to the other patches if you want.
>
Thanks. will do!
--
To unsubscribe from this list: send the line "unsubscribe linux-numa" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
