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numa: introduce machine callback for VCPU to node mapping

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Current default round-robin way of distributing VCPUs among
NUMA nodes might be wrong in case on multi-core/threads
CPUs. Making guests confused wrt topology where cores from
the same socket are on different nodes.

Allow a machine to override default mapping by providing
 MachineClass::cpu_index_to_socket_id()
callback which would allow it group VCPUs from a socket
on the same NUMA node.

Signed-off-by: Igor Mammedov <imammedo@redhat.com>
Reviewed-by: Andreas Färber <afaerber@suse.de>
Signed-off-by: Eduardo Habkost <ehabkost@redhat.com>
This commit is contained in:
Igor Mammedov 2015-03-19 17:09:21 +00:00 • committed by Eduardo Habkost
parent 3ef7197505
commit 57924bcd87
4 changed files with 21 additions and 7 deletions
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18
numa.c
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@ -202,7 +202,7 @@ static void validate_numa_cpus(void)
}
}
void parse_numa_opts(void)
void parse_numa_opts(MachineClass *mc)
{
int i;
@ -270,13 +270,21 @@ void parse_numa_opts(void)
break;
}
}
/* assigning the VCPUs round-robin is easier to implement, guest OSes
* must cope with this anyway, because there are BIOSes out there in
* real machines which also use this scheme.
/* Historically VCPUs were assigned in round-robin order to NUMA
* nodes. However it causes issues with guest not handling it nice
* in case where cores/threads from a multicore CPU appear on
* different nodes. So allow boards to override default distribution
* rule grouping VCPUs by socket so that VCPUs from the same socket
* would be on the same node.
*/
if (i == nb_numa_nodes) {
for (i = 0; i < max_cpus; i++) {
set_bit(i, numa_info[i % nb_numa_nodes].node_cpu);
unsigned node_id = i % nb_numa_nodes;
if (mc->cpu_index_to_socket_id) {
node_id = mc->cpu_index_to_socket_id(i) % nb_numa_nodes;
}
set_bit(i, numa_info[node_id].node_cpu);
}
}