On Thu, Mar 4, 2021 at 4:02 PM Dave Hansen <dave.hansen@xxxxxxxxxxxxxxx> wrote:
>
>
> From: Dave Hansen <dave.hansen@xxxxxxxxxxxxxxx>
>
> Global reclaim aims to reduce the amount of memory used on
> a given node or set of nodes. Migrating pages to another
> node serves this purpose.
>
> memcg reclaim is different. Its goal is to reduce the
> total memory consumption of the entire memcg, across all
> nodes. Migration does not assist memcg reclaim because
> it just moves page contents between nodes rather than
> actually reducing memory consumption.
Reviewed-by: Yang Shi <shy828301@xxxxxxxxx>
>
> Signed-off-by: Dave Hansen <dave.hansen@xxxxxxxxxxxxxxx>
> Suggested-by: Yang Shi <yang.shi@xxxxxxxxxxxxxxxxx>
> Cc: David Rientjes <rientjes@xxxxxxxxxx>
> Cc: Huang Ying <ying.huang@xxxxxxxxx>
> Cc: Dan Williams <dan.j.williams@xxxxxxxxx>
> Cc: David Hildenbrand <david@xxxxxxxxxx>
> Cc: osalvador <osalvador@xxxxxxx>
> ---
>
> b/mm/vmscan.c | 18 ++++++++++++------
> 1 file changed, 12 insertions(+), 6 deletions(-)
>
> diff -puN mm/vmscan.c~never-demote-for-memcg-reclaim mm/vmscan.c
> --- a/mm/vmscan.c~never-demote-for-memcg-reclaim 2021-03-04 15:36:01.067806417 -0800
> +++ b/mm/vmscan.c 2021-03-04 15:36:01.072806417 -0800
> @@ -288,7 +288,8 @@ static bool writeback_throttling_sane(st
> #endif
>
> static inline bool can_reclaim_anon_pages(struct mem_cgroup *memcg,
> - int node_id)
> + int node_id,
> + struct scan_control *sc)
> {
> if (memcg == NULL) {
> /*
> @@ -326,7 +327,7 @@ unsigned long zone_reclaimable_pages(str
>
> nr = zone_page_state_snapshot(zone, NR_ZONE_INACTIVE_FILE) +
> zone_page_state_snapshot(zone, NR_ZONE_ACTIVE_FILE);
> - if (can_reclaim_anon_pages(NULL, zone_to_nid(zone)))
> + if (can_reclaim_anon_pages(NULL, zone_to_nid(zone), NULL))
> nr += zone_page_state_snapshot(zone, NR_ZONE_INACTIVE_ANON) +
> zone_page_state_snapshot(zone, NR_ZONE_ACTIVE_ANON);
>
> @@ -1063,7 +1064,8 @@ static enum page_references page_check_r
> return PAGEREF_RECLAIM;
> }
>
> -static bool migrate_demote_page_ok(struct page *page)
> +static bool migrate_demote_page_ok(struct page *page,
> + struct scan_control *sc)
> {
> int next_nid = next_demotion_node(page_to_nid(page));
>
> @@ -1071,6 +1073,10 @@ static bool migrate_demote_page_ok(struc
> VM_BUG_ON_PAGE(PageHuge(page), page);
> VM_BUG_ON_PAGE(PageLRU(page), page);
>
> + /* It is pointless to do demotion in memcg reclaim */
> + if (cgroup_reclaim(sc))
> + return false;
> +
> if (next_nid == NUMA_NO_NODE)
> return false;
> if (PageTransHuge(page) && !thp_migration_supported())
> @@ -1326,7 +1332,7 @@ retry:
> * Before reclaiming the page, try to relocate
> * its contents to another node.
> */
> - if (do_demote_pass && migrate_demote_page_ok(page)) {
> + if (do_demote_pass && migrate_demote_page_ok(page, sc)) {
> list_add(&page->lru, &demote_pages);
> unlock_page(page);
> continue;
> @@ -2371,7 +2377,7 @@ static void get_scan_count(struct lruvec
> enum lru_list lru;
>
> /* If we have no swap space, do not bother scanning anon pages. */
> - if (!sc->may_swap || !can_reclaim_anon_pages(memcg, pgdat->node_id)) {
> + if (!sc->may_swap || !can_reclaim_anon_pages(memcg, pgdat->node_id, sc)) {
> scan_balance = SCAN_FILE;
> goto out;
> }
> @@ -2746,7 +2752,7 @@ static inline bool should_continue_recla
> */
> pages_for_compaction = compact_gap(sc->order);
> inactive_lru_pages = node_page_state(pgdat, NR_INACTIVE_FILE);
> - if (can_reclaim_anon_pages(NULL, pgdat->node_id))
> + if (can_reclaim_anon_pages(NULL, pgdat->node_id, sc))
> inactive_lru_pages += node_page_state(pgdat, NR_INACTIVE_ANON);
>
> return inactive_lru_pages > pages_for_compaction;
> _
>
