Messages in this thread | | | Date | Fri, 17 Jul 2009 09:57:45 +0900 | From | KAMEZAWA Hiroyuki <> | Subject | Re: [BUG] set_mempolicy(MPOL_INTERLEAV) cause kernel panic |
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On Fri, 17 Jul 2009 09:04:46 +0900 (JST) KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com> wrote:
> > On Wed, 15 Jul 2009, Lee Schermerhorn wrote: > > > > > Interestingly, on ia64, the top cpuset mems_allowed gets set to all > > > possible nodes, while on x86_64, it gets set to on-line nodes [or nodes > > > with memory]. Maybe this is a to support hot-plug? > > > > > > > numactl --interleave=all simply passes a nodemask with all bits set, so if > > cpuset_current_mems_allowed includes offline nodes from node_possible_map, > > then mpol_set_nodemask() doesn't mask them off. > > > > Seems like we could handle this strictly in mempolicies without worrying > > about top_cpuset like in the following? > > This patch seems band-aid patch. it will change memory-hotplug behavior. > Please imazine following scenario: > > 1. numactl interleave=all process-A > 2. memory hot-add > > before 2.6.30: > -> process-A can use hot-added memory > > your proposal patch: > -> process-A can't use hot-added memory >
IMHO, the application itseld should be notifed to change its mempolicy by hot-plug script on the host. While an application uses interleave, a new node hot-added is just a noise. I think "How pages are interleaved" should not be changed implicitly. Then, checking at set_mempolicy() seems sane. If notified, application can do page migration and rebuild his mapping in ideal way.
BUT I don't linke init->mem_allowed contains N_POSSIBLE...it should be initialized to N_HIGH_MEMORY, IMHO.
Thanks, -Kame
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