The patch titled
Subject: powerpc/numa: set numa_node for all possible cpus
has been added to the -mm tree. Its filename is
powerpc-numa-set-numa_node-for-all-possible-cpus.patch
This patch should soon appear at
http://ozlabs.org/~akpm/mmots/broken-out/powerpc-numa-set-numa_node-for-all-possible-cpus.patch
and later at
http://ozlabs.org/~akpm/mmotm/broken-out/powerpc-numa-set-numa_node-for-all-possible-cpus.patch
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------------------------------------------------------
From: Srikar Dronamraju <srikar@xxxxxxxxxxxxxxxxxx>
Subject: powerpc/numa: set numa_node for all possible cpus
Patch series "Offline memoryless cpuless node 0", v5.
Linux kernel configured with CONFIG_NUMA on a system with multiple
possible nodes, marks node 0 as online at boot. However in practice,
there are systems which have node 0 as memoryless and cpuless.
This can cause
1. numa_balancing to be enabled on systems with only one online node.
2. Existence of dummy (cpuless and memoryless) node which can confuse
users/scripts looking at output of lscpu / numactl.
This patchset wants to correct this anomaly.
This should only affect systems that have CONFIG_MEMORYLESS_NODES.
Currently there are only 2 architectures ia64 and powerpc that have
this config.
Note: Patch 3 in this patch series depends on patches 1 and 2. Without
patches 1 and 2, patch 3 might crash powerpc.
This patch (of 3):
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.
Link: http://lkml.kernel.org/r/20200624092846.9194-1-srikar@xxxxxxxxxxxxxxxxxx
Link: http://lkml.kernel.org/r/20200624092846.9194-2-srikar@xxxxxxxxxxxxxxxxxx
Signed-off-by: Srikar Dronamraju <srikar@xxxxxxxxxxxxxxxxxx>
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: Gautham R Shenoy <ego@xxxxxxxxxxxxxxxxxx>
Cc: Satheesh Rajendran <sathnaga@xxxxxxxxxxxxxxxxxx>
Cc: David Hildenbrand <david@xxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
arch/powerpc/mm/numa.c | 16 +++++++++++++++-
1 file changed, 15 insertions(+), 1 deletion(-)
--- a/arch/powerpc/mm/numa.c~powerpc-numa-set-numa_node-for-all-possible-cpus
+++ a/arch/powerpc/mm/numa.c
@@ -506,6 +506,11 @@ static int numa_setup_cpu(unsigned long
int fcpu = cpu_first_thread_sibling(lcpu);
int nid = NUMA_NO_NODE;
+ if (!cpu_present(lcpu)) {
+ set_cpu_numa_node(lcpu, first_online_node);
+ return first_online_node;
+ }
+
/*
* If a valid cpu-to-node mapping is already available, use it
* directly instead of querying the firmware, since it represents
@@ -931,8 +936,17 @@ void __init mem_topology_setup(void)
reset_numa_cpu_lookup_table();
- for_each_present_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.
+ */
numa_setup_cpu(cpu);
+ }
}
void __init initmem_init(void)
_
Patches currently in -mm which might be from srikar@xxxxxxxxxxxxxxxxxx are
powerpc-numa-set-numa_node-for-all-possible-cpus.patch
powerpc-numa-prefer-node-id-queried-from-vphn.patch
mm-page_alloc-keep-memoryless-cpuless-node-0-offline.patch
