On Wed 11-03-20 16:32:35, Srikar Dronamraju wrote: > A Powerpc system with multiple possible nodes and with CONFIG_NUMA > enabled always used to have a node 0, even if node 0 does not any cpus > or memory attached to it. As per PAPR, node affinity of a cpu is only > available once its present / online. For all cpus that are possible but > not present, cpu_to_node() would point to node 0. > > To ensure a cpuless, memoryless dummy node is not online, powerpc need > to make sure all possible but not present cpu_to_node are set to a > proper node. Just curious, is this somehow related to http://lkml.kernel.org/r/20200227182650.GG3771@xxxxxxxxxxxxxx? > Cc: linuxppc-dev@xxxxxxxxxxxxxxxx > Cc: linux-mm@xxxxxxxxx > Cc: linux-kernel@xxxxxxxxxxxxxxx > Cc: Michal Hocko <mhocko@xxxxxxxx> > Cc: Mel Gorman <mgorman@xxxxxxx> > Cc: Vlastimil Babka <vbabka@xxxxxxx> > Cc: "Kirill A. Shutemov" <kirill@xxxxxxxxxxxxx> > Cc: Christopher Lameter <cl@xxxxxxxxx> > Cc: Michael Ellerman <mpe@xxxxxxxxxxxxxx> > Cc: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> > Cc: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx> > Signed-off-by: Srikar Dronamraju <srikar@xxxxxxxxxxxxxxxxxx> > --- > arch/powerpc/mm/numa.c | 16 ++++++++++++++-- > 1 file changed, 14 insertions(+), 2 deletions(-) > > diff --git a/arch/powerpc/mm/numa.c b/arch/powerpc/mm/numa.c > index 8a399db..54dcd49 100644 > --- a/arch/powerpc/mm/numa.c > +++ b/arch/powerpc/mm/numa.c > @@ -931,8 +931,20 @@ void __init mem_topology_setup(void) > > reset_numa_cpu_lookup_table(); > > - for_each_present_cpu(cpu) > - numa_setup_cpu(cpu); > + for_each_possible_cpu(cpu) { > + /* > + * Powerpc with CONFIG_NUMA always used to have a node 0, > + * even if it was memoryless or cpuless. For all cpus that > + * are possible but not present, cpu_to_node() would point > + * to node 0. To remove a cpuless, memoryless dummy node, > + * powerpc need to make sure all possible but not present > + * cpu_to_node are set to a proper node. > + */ > + if (cpu_present(cpu)) > + numa_setup_cpu(cpu); > + else > + set_cpu_numa_node(cpu, first_online_node); > + } > } > > void __init initmem_init(void) > -- > 1.8.3.1 -- Michal Hocko SUSE Labs
