On Wed, 8 Jul 2026 12:29:06 +0530 Sayali Patil <[email protected]> wrote:
> The KSM NUMA merge test allocates identical pages on different NUMA
> nodes and verifies KSM behavior with merge_across_nodes enabled and
> disabled.
>
> On systems with memoryless NUMA nodes, for example:
> #numactl -H
> available: 2 nodes (0,4)
> .....
> node 0 cpus: 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15
> node 0 size: 14825 MB
> node 0 free: 1382 MB
> node 4 cpus:
> node 4 size: 0 MB
> node 4 free: 0 MB
>
> the test may attempt to allocate memory on a node without memory,
> causing numa_alloc_onnode() to fail and resulting in a spurious test
> failure.
>
> The test currently checks numa_num_configured_nodes() to determine
> whether sufficient NUMA nodes are available. However, configured nodes
> do not necessarily have memory.
>
> Reuse the existing get_first_mem_node() and get_next_mem_node()
> helpers to locate NUMA nodes that actually contain memory, and skip
> the test when fewer than two such nodes are available.
>
> Before patch:
> ---------------------------
> running ./ksm_tests -N -m 1
> ---------------------------
> mbind: Invalid argument
> ok 1 KSM NUMA merging
> Totals: pass:1 fail:0 xfail:0 xpass:0 skip:0 error:0
> [PASS]
> ok 1 ksm_tests -N -m 1
> ---------------------------
> running ./ksm_tests -N -m 0
> ---------------------------
> mbind: Invalid argument
> not ok 1 KSM NUMA merging
> Totals: pass:0 fail:1 xfail:0 xpass:0 skip:0 error:0
> [FAIL]
> not ok 2 ksm_tests -N -m 0 # exit=1
>
> After patch:
> ---------------------------
> running ./ksm_tests -N -m 1
> ---------------------------
> At least 2 NUMA nodes with memory must be available
> ok 1
> SKIP KSM NUMA merging
> Totals: pass:0 fail:0 xfail:0 xpass:0 skip:1 error:0
> [PASS]
> ok 1 ksm_tests -N -m 1
> ---------------------------
> running ./ksm_tests -N -m 0
> ---------------------------
> At least 2 NUMA nodes with memory must be available
> ok 1
> SKIP KSM NUMA merging
> Totals: pass:0 fail:0 xfail:0 xpass:0 skip:1 error:0
> [PASS]
> ok 2 ksm_tests -N -m 0
>
> Fixes: e3820ab252dd ("selftest/vm: fix ksm selftest to run with different
> NUMA topologies")
> Co-developed-by: David Hildenbrand (Arm) <[email protected]>
> Signed-off-by: David Hildenbrand (Arm) <[email protected]>
> Signed-off-by: Sayali Patil <[email protected]>
> ---
> tools/testing/selftests/mm/ksm_tests.c | 16 +++++++++-------
> 1 file changed, 9 insertions(+), 7 deletions(-)
>
Acked-by: Usama Arif <[email protected]>
