* Michal Hocko <mhocko@xxxxxxxxxx> [2020-03-11 12:57:35]: > 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? > The issue I am trying to fix is a known issue in Powerpc since many years. So this surely not a problem after a75056fc1e7c (mm/memcontrol.c: allocate shrinker_map on appropriate NUMA node"). I tried v5.6-rc4 + a75056fc1e7c but didnt face any issues booting the kernel. Will work with Sachin/Abdul (reporters of the issue). > > 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 -- Thanks and Regards Srikar Dronamraju
