[Pmem] Re: [PATCH] mm: tiered: Do not promotion when tiered memory is turned off

ANBZ: #80 sysctl_numa_balancing_mode is set to NUMA_BALANCING_MEMORY_TIERING allowing memory migration between fast and slow node, and the page of slow memory reuse the cpupid field. But it will bring in the issue when sysctl_numa_balancing_mode is turned off dynamtically. should_numa_migrate_memory will choose whether the slow memory should be migrated to fast memory when NUMA_BALANCING_MEMORY_TIERING is turned off simultaneously. It will fails to obtain the correct node from cpupid field in slow memory. hence it will trigger the panic. Signed-off-by: zhongjiang-ali <zhongjiang-ali(a)linux.alibaba.com>

--- kernel/sched/fair.c | 8 ++++++++ 1 file changed, 8 insertions(+) diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c index 0184145..6afa935 100644 --- a/kernel/sched/fair.c +++ b/kernel/sched/fair.c @@ -3016,6 +3016,14 @@ bool should_numa_migrate_memory(struct task_struct *p, struct page * page, last_cpupid = page_cpupid_xchg_last(page, this_cpupid); /* + * Migration will turn off between fast memory and slow node when + * sysctl_numa_balancing_mode disable the feature dynamically. + */ + if (!(sysctl_numa_balancing_mode & NUMA_BALANCING_MEMORY_TIERING) && + !node_is_toptier(src_nid)) + return false; + + /* * Allow first faults or private faults to migrate immediately early in * the lifetime of a task. The magic number 4 is based on waiting for * two full passes of the "multi-stage node selection" test that is