14 Jan
2022
14 Jan
'22
12:03 a.m.
On 2022/1/13 7:30 下午, Huang, Ying wrote:
zhong jiang <zhongjiang-ali(a)linux.alibaba.com>
writes:
Yes, I think so
On 2022/1/13 4:13 H, Huang, Ying wrote:
It seems that nr_cpu_ids is the right choice. Yes?
zhong jiang
<zhongjiang-ali(a)linux.alibaba.com> writes:
but It will make nr_cpumask_bits equal to NR_CPUS when
CONFIG_CPUMASK_OFFSTACK=n.
The cpu excess nr_cpu_ids should has the some issue.
On 2022/1/13 9:02 H, Huang, Ying wrote:
> zhong jiang <zhongjiang-ali(a)linux.alibaba.com> writes:
>
>> Read tthe patch again, see the following issue.
>>
>> On 2022/1/12 11:02
H, Huang, Ying wrote:
>>> 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 <ying.huang(a)intel.com>
>>> 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;
>>> +}
>>> +
>> Oops. s/>=/</
> Oops! Thanks for pointing this out. Have you tested your revised version?
I think nr_cpumask_bits should be replaced with
num_possible_cpus(), We should can not parse the cpu beyond
max_possible_cpus , is it right ?
If my understanding to the following code were correct, they are same in
most situations,
Best Regards,
Huang, Ying
>> void __init setup_nr_cpu_ids(void)
>> {
>> nr_cpu_ids = find_last_bit(cpumask_bits(cpu_possible_mask),NR_CPUS) + 1;
>> }
>>
>> And in theory, it's possible that there are "holes" in
cpu_possible_mask.
>>
>> Best Regards,
>> Huang, Ying
>>
>>> Thanks,
>>>
>>> zhong jiang
>>>
>>>> Best Regards,
>>>> Huang, Ying
>>>>
>>>>>> #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
*/
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