* Aneesh Kumar K.V <aneesh.ku...@linux.ibm.com> [2022-06-23 18:24:42]:
> While building the cpu_to_node map make sure we always use the online node > to build the mapping table. In general this should not be an issue > because the kernel use similar lookup mechanism (vphn_get_nid()) to mark > nodes online (setup_node_data()). Hence NUMA nodes we find during > lookup in numa_setup_cpu() will always be found online. > > To keep logic simpler/correct, make sure that if the hypervisor > or device tree returned a not online node, don't use that to build > the map table. Instead, use the first_online_node. Why should the returned nid be already online. Are we facing any problem with the current code? Since general idea is to keep cpu_to_node constant, By assigining it the first_online_node, we may be ending up assigning a wrong node, resulting a performance penalty later on. i.e CPU may actually belong to node 4 but we assigned it to node 1. Also the coregroup id is derived from associavity array. If there is a mismatch between the coregroup id and nid, scheduler will crib. > > Signed-off-by: Aneesh Kumar K.V <aneesh.ku...@linux.ibm.com> > --- > arch/powerpc/mm/numa.c | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/arch/powerpc/mm/numa.c b/arch/powerpc/mm/numa.c > index 0801b2ce9b7d..f387b9eb9dc9 100644 > --- a/arch/powerpc/mm/numa.c > +++ b/arch/powerpc/mm/numa.c > @@ -741,7 +741,7 @@ static int numa_setup_cpu(unsigned long lcpu) > of_node_put(cpu); > > out_present: > - if (nid < 0 || !node_possible(nid)) > + if (nid < 0 || !node_online(nid)) > nid = first_online_node; > > /* > -- > 2.36.1 > -- Thanks and Regards Srikar Dronamraju
