last_cpupid is only available when memory tiering is off or the folio is in toptier node. Complete the check to read last_cpupid when it is available. Before the fix, the default last_cpupid will be used even if memory tiering mode is turned off at runtime instead of the actual value. This can prevent task_numa_fault() from getting right numa fault stats, but should not cause any crash. User might see performance changes after the fix. Reported-by: David Hildenbrand <david@xxxxxxxxxx> Closes: https://lore.kernel.org/linux-mm/9af34a6b-ca56-4a64-8aa6-ade65f109288@xxxxxxxxxx/ Fixes: 33024536bafd ("memory tiering: hot page selection with hint page fault latency") Signed-off-by: Zi Yan <ziy@xxxxxxxxxx> Reviewed-by: "Huang, Ying" <ying.huang@xxxxxxxxx> Reviewed-by: Baolin Wang <baolin.wang@xxxxxxxxxxxxxxxxx> Acked-by: David Hildenbrand <david@xxxxxxxxxx> Reviewed-by: Kefeng Wang <wangkefeng.wang@xxxxxxxxxx> --- mm/huge_memory.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) diff --git a/mm/huge_memory.c b/mm/huge_memory.c index 88dffc0023b5..15234b2e252e 100644 --- a/mm/huge_memory.c +++ b/mm/huge_memory.c @@ -1707,7 +1707,8 @@ vm_fault_t do_huge_pmd_numa_page(struct vm_fault *vmf) * For memory tiering mode, cpupid of slow memory page is used * to record page access time. So use default value. */ - if (node_is_toptier(nid)) + if (!(sysctl_numa_balancing_mode & NUMA_BALANCING_MEMORY_TIERING) || + node_is_toptier(nid)) last_cpupid = folio_last_cpupid(folio); target_nid = numa_migrate_prep(folio, vmf, haddr, nid, &flags); if (target_nid == NUMA_NO_NODE) -- 2.43.0
