Currently Linux kernel 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 numa_balancing to be enabled on systems with only one node
with memory and CPUs. The existence of this dummy node which is cpuless and
memoryless node can confuse users/scripts looking at output of lscpu /
numactl.
Lets stop assuming that Node 0 is always online.
v5.6-rc4
available: 2 nodes (0,2)
node 0 cpus:
node 0 size: 0 MB
node 0 free: 0 MB
node 2 cpus: 0 1 2 3 4 5 6 7
node 2 size: 32625 MB
node 2 free: 31490 MB
node distances:
node 0 2
0: 10 20
2: 20 10
proc and sys files
------------------
/sys/devices/system/node/online: 0,2
/proc/sys/kernel/numa_balancing: 1
/sys/devices/system/node/has_cpu: 2
/sys/devices/system/node/has_memory: 2
/sys/devices/system/node/has_normal_memory: 2
/sys/devices/system/node/possible: 0-31
v5.6-rc4 + patch
------------------
available: 1 nodes (2)
node 2 cpus: 0 1 2 3 4 5 6 7
node 2 size: 32625 MB
node 2 free: 31487 MB
node distances:
node 2
2: 10
proc and sys files
------------------
/sys/devices/system/node/online: 2
/proc/sys/kernel/numa_balancing: 0
/sys/devices/system/node/has_cpu: 2
/sys/devices/system/node/has_memory: 2
/sys/devices/system/node/has_normal_memory: 2
/sys/devices/system/node/possible: 0-31
Cc: linuxppc-dev@lists.ozlabs.org
Cc: linux...@kvack.org
Cc: linux-ker...@vger.kernel.org
Cc: Michal Hocko <mho...@suse.com>
Cc: Mel Gorman <mgor...@suse.de>
Cc: Vlastimil Babka <vba...@suse.cz>
Cc: "Kirill A. Shutemov" <kir...@shutemov.name>
Cc: Christopher Lameter <c...@linux.com>
Cc: Michael Ellerman <m...@ellerman.id.au>
Cc: Andrew Morton <a...@linux-foundation.org>
Cc: Linus Torvalds <torva...@linux-foundation.org>
Signed-off-by: Srikar Dronamraju <sri...@linux.vnet.ibm.com>
---
mm/page_alloc.c | 4 +++-
1 file changed, 3 insertions(+), 1 deletion(-)
diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index 3c4eb75..68e635f4 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -116,8 +116,10 @@ struct pcpu_drain {
*/
nodemask_t node_states[NR_NODE_STATES] __read_mostly = {
[N_POSSIBLE] = NODE_MASK_ALL,
+#ifdef CONFIG_NUMA
+ [N_ONLINE] = NODE_MASK_NONE,
+#else
[N_ONLINE] = { { [0] = 1UL } },
-#ifndef CONFIG_NUMA
[N_NORMAL_MEMORY] = { { [0] = 1UL } },
#ifdef CONFIG_HIGHMEM
[N_HIGH_MEMORY] = { { [0] = 1UL } },
--
1.8.3.1
