linux-kernel - Re: [PATCH 1/2] memory tiering: read last_cpupid correctly in do_huge_pmd_numa

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Message-ID: <22C21849-7ED8-4F89-B7B6-81CA3EBAC4D4@nvidia.com>
Date: Sat, 20 Jul 2024 08:36:27 -0400
From: Zi Yan <ziy@...dia.com>
To: Kefeng Wang <wangkefeng.wang@...wei.com>
Cc: Andrew Morton <akpm@...ux-foundation.org>, linux-mm@...ck.org,
 David Hildenbrand <david@...hat.com>, "Huang, Ying" <ying.huang@...el.com>,
 Baolin Wang <baolin.wang@...ux.alibaba.com>, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/2] memory tiering: read last_cpupid correctly in
 do_huge_pmd_numa_page()

On 20 Jul 2024, at 4:11, Kefeng Wang wrote:

> On 2024/7/19 22:43, Zi Yan wrote:
>> 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.
>>
>> Reported-by: David Hildenbrand <david@...hat.com>
>> Closes: https://lore.kernel.org/linux-mm/9af34a6b-ca56-4a64-8aa6-ade65f109288@redhat.com/
>> Fixes: 33024536bafd ("memory tiering: hot page selection with hint page fault latency")
>> Signed-off-by: Zi Yan <ziy@...dia.com>
>> Reviewed-by: "Huang, Ying" <ying.huang@...el.com>
>> Reviewed-by: Baolin Wang <baolin.wang@...ux.alibaba.com>
>> Acked-by: David Hildenbrand <david@...hat.com>
>
> Reviewed-by: Kefeng Wang <wangkefeng.wang@...wei.com>
>
> and we better to check numabalance mode in migrate_misplaced_folio()?
>
> --- a/mm/migrate.c
> +++ b/mm/migrate.c
> @@ -2630,7 +2630,8 @@ int migrate_misplaced_folio(struct folio *folio, struct vm_area_struct *vma,
>                 putback_movable_pages(&migratepages);
>         if (nr_succeeded) {
>                 count_vm_numa_events(NUMA_PAGE_MIGRATE, nr_succeeded);
> -               if (!node_is_toptier(folio_nid(folio)) && node_is_toptier(node))
> +               if ((sysctl_numa_balancing_mode & NUMA_BALANCING_MEMORY_TIERING)
> +                   &&!node_is_toptier(folio_nid(folio)) && node_is_toptier(node))
>                         mod_node_page_state(pgdat, PGPROMOTE_SUCCESS,
>                                             nr_succeeded);
>         }

Yes, will add this as a separate fix. Thanks.

--
Best Regards,
Yan, Zi

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