On Mon, Jul 25, 2016 at 10:14:18AM +0200, Igor Mammedov wrote: > On Mon, 25 Jul 2016 16:09:04 +1000 > David Gibson <da...@gibson.dropbear.id.au> wrote: > > > On Wed, Jul 20, 2016 at 09:01:11AM +0200, Peter Krempa wrote: > > > On Wed, Jul 20, 2016 at 11:00:05 +1000, David Gibson wrote: > > > > On Tue, Jul 19, 2016 at 01:52:40PM +0200, Peter Krempa wrote: > > > > > On Mon, Jul 18, 2016 at 19:19:19 +1000, David Gibson wrote: > > > > > > The spapr implementation of query-hotpluggable-cpus builds the list > > > > > > of > > > > > > hotpluggable cores from the end (most removed from the list head) > > > > > > because that's the easiest way with a singly linked list. Because > > > > > > it > > > > > > also traverses the possible CPU cores starting from low indexes the > > > > > > resulting list has the cpu cores listed in reverse order by core-id. > > > > > > > > > > > > That's not generally harmful, but it means the output from "info > > > > > > hotpluggable-cpus" is a little harder to read than it could be. > > > > > > > > > > > > Therefore, traverse the cpus in reverse order so that the final list > > > > > > ends up in increasing-core-id order. > > > > > > > > > > To make this interface usable with in-order hotplug the ordering of > > > > > the > > > > > entries should be codified in the schema documentation. (see my > > > > > response > > > > > on the cover letter for justification). > > > > > > > > I'm not really sure what you mean by this. > > > > > > Currently the order of entries in reply of query-hotpluggable-cpus is > > > arbitrary as this patch hints. > > > > > > If qemu won't support arbitrary order hotplug but libvirt should be able > > > to use the new interface, then the order of replies of > > > query-hotpluggable-cpus need to corelate (in a documented fashion) with > > > the order we need to plug the cpus in. By not documenting any order > > > libvirt can just guess it (by reimplementing the algorithm in qemu). > > > > > > I've pointed this out in a sub-thread of the cover-letter. > > > > So, based on Peter's comments (and others) I've concluded that the > > cpu-add implementation in terms of the new interface isn't really > > useful. > > > > However, I think this re-ordering is still a good idea, because: > > * It makes info hotpluggable-cpus easier to read in the HMP > > > > * Although we certainly need a better approach to handling hotplug + > > NUMA, correcting the order should allow the existing NUMA > > interface to work with only as much guesswork in libvirt as we > > already have. > > > > * We haven't released a qemu with query-hotpluggable-cpus yet, so we > > shouldn't need version conditions in order to use the order. > I've talked with Peter and meanwhile (till we have sane NUMA interface) > libvirt will be guessing ids based on query-hotpluggable-cpus output > sorted by socket/core/thread-id, so forward/reverse order won't really > matter to it. > > Forward sorting is fine wrt 'info hotpluggable-cpus', however it might > be better to do sorting in HMP callback so that each target won't have > to do it nor regress command output in future or introduce another > ordering. > > Considering that ordering affects only HMP won't require any compat > glue even if it's not fixed in 2.7 release.
Hm, ok, I'll drop this patch.
>
> >
> > For that reason I've tentatively merged this patch into ppc-for-2.7.
> > It would be good to get an R-b or A-b from someone before I send a
> > pull request (which I'm hoping to do tomorrow).
> >
>
--
David Gibson | I'll have my music baroque, and my code
david AT gibson.dropbear.id.au | minimalist, thank you. NOT _the_ _other_
| _way_ _around_!
http://www.ozlabs.org/~dgibson
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