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

Hi, Jiang, I failed to reproduce the bug on my side. Could you help me to test whether the below patch can fix the bug? Best Regards, Huang, Ying ------------------------------8<---------------------------------------- From 919db496945d45e2c593470ce84f5d6c50ae95a8 Mon Sep 17 00:00:00 2001 From: Huang Ying &lt;ying.huang(a)intel.com&gt; Date: Mon, 10 Jan 2022 15:29:38 +0800 Subject: [PATCH] Fix panic when disabling memory tiering mode dynamically --- include/linux/mm.h | 5 +++++ kernel/sched/fair.c | 20 +++++++++++++++++--- 2 files changed, 22 insertions(+), 3 deletions(-) diff --git a/include/linux/mm.h b/include/linux/mm.h index a9ea778eafe0..b22e18676d29 100644 --- a/include/linux/mm.h +++ b/include/linux/mm.h @@ -1440,6 +1440,11 @@ static inline bool __cpupid_match_pid(pid_t task_pid, int cpupid) return (task_pid & LAST__PID_MASK) == cpupid_to_pid(cpupid); } +static inline bool check_cpupid(int cpupid) +{ + return cpupid_to_cpu(cpupid) >= nr_cpumask_bits; +} +

#define cpupid_match_pid(task, cpupid) __cpupid_match_pid(task->pid, cpupid) #ifdef LAST_CPUPID_NOT_IN_PAGE_FLAGS static inline int page_cpupid_xchg_last(struct page *page, int cpupid) diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c index 7ca4ab033180..85a01906d796 100644 --- a/kernel/sched/fair.c +++ b/kernel/sched/fair.c @@ -1597,6 +1597,14 @@ bool should_numa_migrate_memory(struct task_struct *p, struct page * page, this_cpupid = cpu_pid_to_cpupid(dst_cpu, current->pid); last_cpupid = page_cpupid_xchg_last(page, this_cpupid); + /* + * The cpupid may be invalid when NUMA_BALANCING_MEMORY_TIERING + * is disabled dynamically. + */ + if (!(sysctl_numa_balancing_mode & NUMA_BALANCING_MEMORY_TIERING) && + !node_is_toptier(src_nid) && !check_cpupid(last_cpupid)) + 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 @@ -2812,9 +2820,15 @@ void task_numa_fault(int last_cpupid, int mem_node, int pages, int flags) if (!p->mm) return; - /* Numa faults statistics are unnecessary for the slow memory node */ - if (sysctl_numa_balancing_mode & NUMA_BALANCING_MEMORY_TIERING && - !node_is_toptier(mem_node)) + /* + * NUMA faults statistics are unnecessary for the slow memory node. + * + * And, the cpupid may be invalid when NUMA_BALANCING_MEMORY_TIERING + * is disabled dynamically. + */ + if (!node_is_toptier(mem_node) && + (sysctl_numa_balancing_mode & NUMA_BALANCING_MEMORY_TIERING || + !check_cpupid(last_cpupid))) return; /* Allocate buffer to track faults on a per-node basis */