| Message ID | 20210401183231.8485C83D@viggo.jf.intel.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | Migrate Pages in lieu of discard | expand |
On Thu, Apr 1, 2021 at 11:35 AM Dave Hansen <dave.hansen@linux.intel.com> wrote: > > > From: Keith Busch <kbusch@kernel.org> > > Reclaim anonymous pages if a migration path is available now that > demotion provides a non-swap recourse for reclaiming anon pages. > > Note that this check is subtly different from the > anon_should_be_aged() checks. This mechanism checks whether a > specific page in a specific context *can* actually be reclaimed, given > current swap space and cgroup limits > > anon_should_be_aged() is a much simpler and more preliminary check > which just says whether there is a possibility of future reclaim. > > #Signed-off-by: Keith Busch <keith.busch@intel.com> > Cc: Keith Busch <kbusch@kernel.org> > Signed-off-by: Dave Hansen <dave.hansen@linux.intel.com> > Reviewed-by: Yang Shi <shy828301@gmail.com> > Cc: Wei Xu <weixugc@google.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> > Cc: osalvador <osalvador@suse.de> > > -- > > Changes from Dave 10/2020: > * remove 'total_swap_pages' modification > > Changes from Dave 06/2020: > * rename reclaim_anon_pages()->can_reclaim_anon_pages() > > Note: Keith's Intel SoB is commented out because he is no > longer at Intel and his @intel.com mail will bounce. > --- > > b/mm/vmscan.c | 35 ++++++++++++++++++++++++++++++++--- > 1 file changed, 32 insertions(+), 3 deletions(-) > > diff -puN mm/vmscan.c~0009-mm-vmscan-Consider-anonymous-pages-without-swap mm/vmscan.c > --- a/mm/vmscan.c~0009-mm-vmscan-Consider-anonymous-pages-without-swap 2021-03-31 15:17:19.388000242 -0700 > +++ b/mm/vmscan.c 2021-03-31 15:17:19.407000242 -0700 > @@ -287,6 +287,34 @@ static bool writeback_throttling_sane(st > } > #endif > > +static inline bool can_reclaim_anon_pages(struct mem_cgroup *memcg, > + int node_id) > +{ > + if (memcg == NULL) { > + /* > + * For non-memcg reclaim, is there > + * space in any swap device? > + */ > + if (get_nr_swap_pages() > 0) > + return true; > + } else { > + /* Is the memcg below its swap limit? */ > + if (mem_cgroup_get_nr_swap_pages(memcg) > 0) > + return true; > + } > + > + /* > + * The page can not be swapped. > + * > + * Can it be reclaimed from this node via demotion? > + */ > + if (next_demotion_node(node_id) >= 0) > + return true; When neither swap space nor RECLAIM_MIGRATE is enabled, but next_demotion_node() is configured, inactive pages cannot be swapped out nor demoted. However, this check can still cause these pages to be sent to shrink_page_list() (e.g., when can_reclaim_anon_pages() is called by get_scan_count()) and make the THP pages being unnecessarily split there. One fix would be to guard this next_demotion_node() check with the RECLAIM_MIGRATE node_reclaim_mode check. This RECLAIM_MIGRATE check needs to be applied to other calls to next_demotion_node() in vmscan.c as well. > + > + /* No way to reclaim anon pages */ > + return false; > +} > + > /* > * This misses isolated pages which are not accounted for to save counters. > * As the data only determines if reclaim or compaction continues, it is > @@ -298,7 +326,7 @@ 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 (get_nr_swap_pages() > 0) > + if (can_reclaim_anon_pages(NULL, zone_to_nid(zone))) > nr += zone_page_state_snapshot(zone, NR_ZONE_INACTIVE_ANON) + > zone_page_state_snapshot(zone, NR_ZONE_ACTIVE_ANON); > > @@ -2323,6 +2351,7 @@ enum scan_balance { > static void get_scan_count(struct lruvec *lruvec, struct scan_control *sc, > unsigned long *nr) > { > + struct pglist_data *pgdat = lruvec_pgdat(lruvec); > struct mem_cgroup *memcg = lruvec_memcg(lruvec); > unsigned long anon_cost, file_cost, total_cost; > int swappiness = mem_cgroup_swappiness(memcg); > @@ -2333,7 +2362,7 @@ 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 || mem_cgroup_get_nr_swap_pages(memcg) <= 0) { > + if (!sc->may_swap || !can_reclaim_anon_pages(memcg, pgdat->node_id)) { Demotion of anon pages still depends on sc->may_swap. Any thoughts on decoupling demotion from swapping more completely? > scan_balance = SCAN_FILE; > goto out; > } > @@ -2708,7 +2737,7 @@ static inline bool should_continue_recla > */ > pages_for_compaction = compact_gap(sc->order); > inactive_lru_pages = node_page_state(pgdat, NR_INACTIVE_FILE); > - if (get_nr_swap_pages() > 0) > + if (can_reclaim_anon_pages(NULL, pgdat->node_id)) > inactive_lru_pages += node_page_state(pgdat, NR_INACTIVE_ANON); > > return inactive_lru_pages > pages_for_compaction; > _ >
diff -puN mm/vmscan.c~0009-mm-vmscan-Consider-anonymous-pages-without-swap mm/vmscan.c --- a/mm/vmscan.c~0009-mm-vmscan-Consider-anonymous-pages-without-swap 2021-03-31 15:17:19.388000242 -0700 +++ b/mm/vmscan.c 2021-03-31 15:17:19.407000242 -0700 @@ -287,6 +287,34 @@ static bool writeback_throttling_sane(st } #endif +static inline bool can_reclaim_anon_pages(struct mem_cgroup *memcg, + int node_id) +{ + if (memcg == NULL) { + /* + * For non-memcg reclaim, is there + * space in any swap device? + */ + if (get_nr_swap_pages() > 0) + return true; + } else { + /* Is the memcg below its swap limit? */ + if (mem_cgroup_get_nr_swap_pages(memcg) > 0) + return true; + } + + /* + * The page can not be swapped. + * + * Can it be reclaimed from this node via demotion? + */ + if (next_demotion_node(node_id) >= 0) + return true; + + /* No way to reclaim anon pages */ + return false; +} + /* * This misses isolated pages which are not accounted for to save counters. * As the data only determines if reclaim or compaction continues, it is @@ -298,7 +326,7 @@ 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 (get_nr_swap_pages() > 0) + if (can_reclaim_anon_pages(NULL, zone_to_nid(zone))) nr += zone_page_state_snapshot(zone, NR_ZONE_INACTIVE_ANON) + zone_page_state_snapshot(zone, NR_ZONE_ACTIVE_ANON); @@ -2323,6 +2351,7 @@ enum scan_balance { static void get_scan_count(struct lruvec *lruvec, struct scan_control *sc, unsigned long *nr) { + struct pglist_data *pgdat = lruvec_pgdat(lruvec); struct mem_cgroup *memcg = lruvec_memcg(lruvec); unsigned long anon_cost, file_cost, total_cost; int swappiness = mem_cgroup_swappiness(memcg); @@ -2333,7 +2362,7 @@ 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 || mem_cgroup_get_nr_swap_pages(memcg) <= 0) { + if (!sc->may_swap || !can_reclaim_anon_pages(memcg, pgdat->node_id)) { scan_balance = SCAN_FILE; goto out; } @@ -2708,7 +2737,7 @@ static inline bool should_continue_recla */ pages_for_compaction = compact_gap(sc->order); inactive_lru_pages = node_page_state(pgdat, NR_INACTIVE_FILE); - if (get_nr_swap_pages() > 0) + if (can_reclaim_anon_pages(NULL, pgdat->node_id)) inactive_lru_pages += node_page_state(pgdat, NR_INACTIVE_ANON); return inactive_lru_pages > pages_for_compaction;