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

[Kefeng Wang]

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@xxxxxxxxxx>
> > > Closes: https://lore.kernel.org/linux-mm/f4ae2c9c-fe40-4807-bdb2-64cf2d716c1a@xxxxxxxxxx/
> > > Fixes: 33024536bafd ("memory tiering: hot page selection with hint page fault latency")
> > > Signed-off-by: Zi Yan <ziy@xxxxxxxxxx>
> >
> > Reviewed-by: Kefeng Wang <wangkefeng.wang@xxxxxxxxxx>
> 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?
>