Re: [PATCH v2 3/3] memory tiering: count PGPROMOTE_SUCCESS when mem tiering is enabled.

[Kefeng Wang <wangkefeng.wang@huawei.com>]

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@huawei.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@nvidia.com>
>>
>> Reviewed-by: Kefeng Wang <wangkefeng.wang@huawei.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?
>