Messages in this thread | | | Date | Tue, 25 Aug 2009 11:13:53 +0200 | From | Andreas Herrmann <> | Subject | Re: [PATCH 13/15] sched: Detect child domain of NUMA (aka NODE) domain |
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On Mon, Aug 24, 2009 at 05:34:18PM +0200, Peter Zijlstra wrote: > On Thu, 2009-08-20 at 15:43 +0200, Andreas Herrmann wrote: > > On multi-node processors a NUMA node might not span a socket. > > Instead a socket might span several NUMA nodes. > > > > This patch introduces a check whether NODE domain is parent > > of MC domain and sets s_data.numa_child_level accordingly. > > (See previous patch for further details.) > > right, except that the previous patch > was rather cryptic :/
Sorry for that.
> So you're proposing to have the NODE level depend on multi-node and then > flip NODE and CPU around?
Conditioned.
Only if a NUMA node does not span an entire socket, e.g. node 0: 0-3 node 1: 4-7 socket 0: 0-3, 4-7
You may have a SRAT that describes one NUMA node containing all sockets, e.g. node 0: 0-7 socket 0 : 0-7 If we have something like that on a multi-node processor system then we don't need to flip NODE and CPU around.
Same is true if there is no SRAT or SRAT is bogus or CONFIG_ACPI_NUMA=n.
In theory, I could also think of node interleaving where a NUMA node spans internal nodes of a socket on a multi-node processor -- no flip in domain hierarchy needed.
On balance, as soon as a socket spans more than one NUMA node we have to flip NODE and CPU.
Regards, Andreas
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