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

["Huang, Ying" <ying.huang@intel.com>]

Kefeng Wang <wangkefeng.wang@huawei.com> writes:

> 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?

Personally, I prefer to use !node_is_toptier() && node_is_toptier()
here.  That sounds more natural for me.

> PS: Could we rename folio_has_cpupid() to folio_has_access_time(),
> even without memory_tiering, we still have cpupid in folio, right?

--
Best Regards,
Huang, Ying