Zi Yan <zi.yan@xxxxxxxx> writes: > From: Zi Yan <ziy@xxxxxxxxxx> > > 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. > > Fixes: 33024536bafd ("memory tiering: hot page selection with hint page fault latency") > Signed-off-by: Zi Yan <ziy@xxxxxxxxxx> Good catch! Thanks! Reviewed-by: "Huang, Ying" <ying.huang@xxxxxxxxx> > --- > 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 d7c84480f1a4..07d9dde4ca33 100644 > --- a/mm/huge_memory.c > +++ b/mm/huge_memory.c > @@ -1705,7 +1705,8 @@ 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)