Re: [RFC][PATCH 6/9] mm/vmscan: add page demotion counter

Yang Shi
2020-10-27T16:41:48Z

On Mon, Oct 19, 2020 at 12:38 AM Huang, Ying <ying.huang@intel.com> wrote:
>
> Dave Hansen <dave.hansen@linux.intel.com> writes:
>
> > From: Yang Shi <yang.shi@linux.alibaba.com>
> >
> > Account the number of demoted pages into reclaim_state->nr_demoted.
>
> It appears that you don't add "nr_demoted" into struct reclaim_state.
>
> > Add pgdemote_kswapd and pgdemote_direct VM counters showed in
> > /proc/vmstat.
> >
> > [ daveh:
> > - __count_vm_events() a bit, and made them look at the THP
> > size directly rather than getting data from migrate_pages()
>
> It appears that we get the data from migrate_pages() now.
>
> > ]
> >
> > Signed-off-by: Yang Shi <yang.shi@linux.alibaba.com>
> > Signed-off-by: Dave Hansen <dave.hansen@linux.intel.com>
> > Cc: David Rientjes <rientjes@google.com>
> > Cc: Huang Ying <ying.huang@intel.com>
> > Cc: Dan Williams <dan.j.williams@intel.com>
> > Cc: David Hildenbrand <david@redhat.com>
> > ---
> >
> > b/include/linux/vm_event_item.h | 2 ++
> > b/mm/vmscan.c | 6 ++++++
> > b/mm/vmstat.c | 2 ++
> > 3 files changed, 10 insertions(+)
> >
> > diff -puN include/linux/vm_event_item.h~mm-vmscan-add-page-demotion-counter include/linux/vm_event_item.h
> > --- a/include/linux/vm_event_item.h~mm-vmscan-add-page-demotion-counter 2020-10-07 09:15:32.171642439 -0700
> > +++ b/include/linux/vm_event_item.h 2020-10-07 09:15:32.179642439 -0700
> > @@ -33,6 +33,8 @@ enum vm_event_item { PGPGIN, PGPGOUT, PS
> > PGREUSE,
> > PGSTEAL_KSWAPD,
> > PGSTEAL_DIRECT,
> > + PGDEMOTE_KSWAPD,
> > + PGDEMOTE_DIRECT,
> > PGSCAN_KSWAPD,
> > PGSCAN_DIRECT,
> > PGSCAN_DIRECT_THROTTLE,
> > diff -puN mm/vmscan.c~mm-vmscan-add-page-demotion-counter mm/vmscan.c
> > --- a/mm/vmscan.c~mm-vmscan-add-page-demotion-counter 2020-10-07 09:15:32.173642439 -0700
> > +++ b/mm/vmscan.c 2020-10-07 09:15:32.180642439 -0700
> > @@ -147,6 +147,7 @@ struct scan_control {
> > unsigned int immediate;
> > unsigned int file_taken;
> > unsigned int taken;
> > + unsigned int demoted;
>
> It appears that this newly added field isn't used in the patch.

My original patch tracked nr_demoted in reclaim_stat as well, but it
seems Dave dropped that part. If Dave thinks it is not necessary to
keep tracking nr_demoted in reclaim_stat, then that field should be
dropped.

>
> > } nr;
> >
> > /* for recording the reclaimed slab by now */
> > @@ -1134,6 +1135,11 @@ static unsigned int demote_page_list(str
> > target_nid, MIGRATE_ASYNC, MR_DEMOTION,
> > &nr_succeeded);
> >
> > + if (current_is_kswapd())
> > + __count_vm_events(PGDEMOTE_KSWAPD, nr_succeeded);
> > + else
> > + __count_vm_events(PGDEMOTE_DIRECT, nr_succeeded);
> > +
> > return nr_succeeded;
> > }
> >
> > diff -puN mm/vmstat.c~mm-vmscan-add-page-demotion-counter mm/vmstat.c
> > --- a/mm/vmstat.c~mm-vmscan-add-page-demotion-counter 2020-10-07 09:15:32.175642439 -0700
> > +++ b/mm/vmstat.c 2020-10-07 09:15:32.181642439 -0700
> > @@ -1244,6 +1244,8 @@ const char * const vmstat_text[] = {
> > "pgreuse",
> > "pgsteal_kswapd",
> > "pgsteal_direct",
> > + "pgdemote_kswapd",
> > + "pgdemote_direct",
> > "pgscan_kswapd",
> > "pgscan_direct",
> > "pgscan_direct_throttle",
> > _
>
> Best Regards,
> Huang, Ying
>