13 Jan
2022
13 Jan
'22
4:13 p.m.
zhong jiang <zhongjiang-ali(a)linux.alibaba.com> writes:
On 2022/1/13 9:02 H, Huang, Ying wrote:
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,
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
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/>=/</
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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