linux-kernel - Re: [PATCH v2 3/3] memory tiering: count PGPROMOTE

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Message-ID: <1621fcbd-38b5-46a8-8b68-911f2920d52e@redhat.com>
Date: Tue, 23 Jul 2024 12:17:56 +0200
From: David Hildenbrand <david@...hat.com>
To: Kefeng Wang <wangkefeng.wang@...wei.com>, Zi Yan <ziy@...dia.com>,
 Andrew Morton <akpm@...ux-foundation.org>, linux-mm@...ck.org
Cc: "Huang, Ying" <ying.huang@...el.com>,
 Baolin Wang <baolin.wang@...ux.alibaba.com>, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 3/3] memory tiering: count PGPROMOTE_SUCCESS when mem
 tiering is enabled.

On 23.07.24 05:24, Kefeng Wang wrote:
> 
> 
> On 2024/7/23 9:54, Zi Yan wrote:
>> On Mon Jul 22, 2024 at 9:48 PM EDT, Kefeng Wang wrote:
>>>
>>>
>>> On 2024/7/23 1:29, Zi Yan wrote:
>>>> memory tiering can be enabled/disabled at runtime and
>>>> sysctl_numa_balancing_mode & NUMA_BALANCING_MEMORY_TIERING is used to check
>>>> it. In migrate_misplaced_folio(), the check is missing when
>>>> PGPROMOTE_SUCCESS is incremented. Add the missing check.
>>>>
>>>> Reported-by: Kefeng Wang <wangkefeng.wang@...wei.com>
>>>> Closes: https://lore.kernel.org/linux-mm/f4ae2c9c-fe40-4807-bdb2-64cf2d716c1a@huawei.com/
>>>> Fixes: 33024536bafd ("memory tiering: hot page selection with hint page fault latency")
>>>> Signed-off-by: Zi Yan <ziy@...dia.com>
>>>
>>> Reviewed-by: Kefeng Wang <wangkefeng.wang@...wei.com>
>>>
>> Thanks.
>>
>>>> ---
>>>>     mm/migrate.c | 4 +++-
>>>>     1 file changed, 3 insertions(+), 1 deletion(-)
>>>>
>>>> diff --git a/mm/migrate.c b/mm/migrate.c
>>>> index bdbb5bb04c91..b819809da470 100644
>>>> --- a/mm/migrate.c
>>>> +++ b/mm/migrate.c
>>>> @@ -2630,7 +2630,9 @@ 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);
>>>
>>> The should be in advance of patch2, and change above to use
>>> folio_has_cpupid() helper() too.
>>
>> It shares the same logic of !folio_has_cpupid() but it might be confusing to
>> put !folio_has_cpupid(folio) && node_is_toptier(node) here. folio's
>> cpupid has nothing to do with the stats here, thus I did not use the
>> function.
> 
> If folio don't include access time, we do migrate it but it isn't a
> promotion, so don't count it, other comments?
> 
> PS: Could we rename folio_has_cpupid() to folio_has_access_time(), even
> without memory_tiering, we still have cpupid in folio, right?

Maybe call it "folio_use_cpupid()" or sth like that? The "has" is a bit 
misleading, because the folio has a cpuid in any case, no?

-- 
Cheers,

David / dhildenb