From 57924bcd87cb03cc21ebd7efed880d16ca048dce Mon Sep 17 00:00:00 2001 From: Igor Mammedov Date: Thu, 19 Mar 2015 17:09:21 +0000 Subject: numa: introduce machine callback for VCPU to node mapping MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit 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 Reviewed-by: Andreas Färber Signed-off-by: Eduardo Habkost --- numa.c | 18 +++++++++++++----- 1 file changed, 13 insertions(+), 5 deletions(-) (limited to 'numa.c') diff --git a/numa.c b/numa.c index 518aedd..fe74e1e 100644 --- a/numa.c +++ b/numa.c @@ -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); } } -- cgit v1.1