All the sibling threads of a core have to be part of the same node.
To ensure that all the sibling threads map to the same node, always
lookup/update the cpu-to-node map of the first thread in the core.
Signed-off-by: Srikar Dronamraju <sri...@linux.vnet.ibm.com>
---
Changelog: v3->v4
As suggested by Nathan, add a warning while mapping offline cpu.
arch/powerpc/mm/numa.c | 22 ++++++++++++++++++++--
1 file changed, 20 insertions(+), 2 deletions(-)
diff --git a/arch/powerpc/mm/numa.c b/arch/powerpc/mm/numa.c
index 8fbe57c..63ec0c3 100644
--- a/arch/powerpc/mm/numa.c
+++ b/arch/powerpc/mm/numa.c
@@ -467,15 +467,20 @@ static int of_drconf_to_nid_single(struct drmem_lmb *lmb)
*/
static int numa_setup_cpu(unsigned long lcpu)
{
- int nid = NUMA_NO_NODE;
struct device_node *cpu;
+ int fcpu = cpu_first_thread_sibling(lcpu);
+ int nid = NUMA_NO_NODE;
/*
* If a valid cpu-to-node mapping is already available, use it
* directly instead of querying the firmware, since it represents
* the most recent mapping notified to us by the platform (eg: VPHN).
+ * Since cpu_to_node binding remains the same for all threads in the
+ * core. If a valid cpu-to-node mapping is already available, for
+ * the first thread in the core, use it.
*/
- if ((nid = numa_cpu_lookup_table[lcpu]) >= 0) {
+ nid = numa_cpu_lookup_table[fcpu];
+ if (nid >= 0) {
map_cpu_to_node(lcpu, nid);
return nid;
}
@@ -496,6 +501,19 @@ static int numa_setup_cpu(unsigned long lcpu)
if (nid < 0 || !node_possible(nid))
nid = first_online_node;
+ /*
+ * Update for the first thread of the core. All threads of a core
+ * have to be part of the same node. This not only avoids querying
+ * for every other thread in the core, but always avoids a case
+ * where virtual node associativity change causes subsequent threads
+ * of a core to be associated with different nid. However if first
+ * thread is already online, expect it to have a valid mapping.
+ */
+ if (fcpu != lcpu) {
+ WARN_ON(cpu_online(fcpu));
+ map_cpu_to_node(fcpu, nid);
+ }
+
map_cpu_to_node(lcpu, nid);
of_node_put(cpu);
out:
--
1.8.3.1
