Re: [PATCH] selftests/mm: skip migration tests if NUMA is unavailable

["David Hildenbrand (Arm)" <david@kernel.org>]

On 2/18/26 17:39, AnishMulay wrote:
> Currently, the migration test asserts that numa_available() returns 0.
> On systems where NUMA is not available (returning -1), such as certain
> ARM64 configurations or single-node systems, this assertion fails and
> crashes the test.

Single-node system (my notebook)

$ ./migration
TAP version 13
1..6
# Starting 6 tests from 1 test cases.
#  RUN           migration.private_anon ...
#      SKIP      Not enough threads or NUMA nodes available
#            OK  migration.private_anon
ok 1 migration.private_anon # SKIP Not enough threads or NUMA nodes 
available
#  RUN           migration.shared_anon ...
#      SKIP      Not enough threads or NUMA nodes available
#            OK  migration.shared_anon
ok 2 migration.shared_anon # SKIP Not enough threads or NUMA nodes available
#  RUN           migration.private_anon_thp ...
#      SKIP      Not enough threads or NUMA nodes available
#            OK  migration.private_anon_thp
ok 3 migration.private_anon_thp # SKIP Not enough threads or NUMA nodes 
available
#  RUN           migration.shared_anon_thp ...
#      SKIP      Not enough threads or NUMA nodes available
#            OK  migration.shared_anon_thp
ok 4 migration.shared_anon_thp # SKIP Not enough threads or NUMA nodes 
available
#  RUN           migration.private_anon_htlb ...
#      SKIP      Not enough threads or NUMA nodes available
#            OK  migration.private_anon_htlb
ok 5 migration.private_anon_htlb # SKIP Not enough threads or NUMA nodes 
available
#  RUN           migration.shared_anon_htlb ...
#      SKIP      Not enough threads or NUMA nodes available
#            OK  migration.shared_anon_htlb
ok 6 migration.shared_anon_htlb # SKIP Not enough threads or NUMA nodes 
available
# PASSED: 6 / 6 tests passed.
# 6 skipped test(s) detected. Consider enabling relevant config options 
to improve coverage.
# Totals: pass:0 fail:0 xfail:0 xpass:0 skip:6 error:0


What numa_available() really checks is if the kernel supports NUMA by 
trying get_mempolicy(). If that fails with ENOSYS or EPERM.

That should mostly (cases we care about) be the case if the kernel is 
compiled without CONFIG_NUMA.

So a better description here would be "On kernels without CONFIG_NUMA, 
this assertion ..."

Given that tools/testing/selftests/mm/config does not include 
CONFIG_NUMA, I think we want to add here

Fixes: 0c2d08728470b ("mm: add selftests for migration entries")

Acked-by: David Hildenbrand (Arm) <david@kernel.org>

-- 
Cheers,

David