From: Johannes Weiner <hannes@xxxxxxxxxxx> Subject: mm: vmscan: harmonize writeback congestion tracking for nodes & memcgs The current writeback congestion tracking has separate flags for kswapd reclaim (node level) and cgroup limit reclaim (memcg-node level). This is unnecessarily complicated: the lruvec is an existing abstraction layer for that node-memcg intersection. Introduce lruvec->flags and LRUVEC_CONGESTED. Then track that at the reclaim root level, which is either the NUMA node for global reclaim, or the cgroup-node intersection for cgroup reclaim. Link: http://lkml.kernel.org/r/20191022144803.302233-9-hannes@xxxxxxxxxxx Signed-off-by: Johannes Weiner <hannes@xxxxxxxxxxx> Reviewed-by: Roman Gushchin <guro@xxxxxx> Reviewed-by: Shakeel Butt <shakeelb@xxxxxxxxxx> Cc: Michal Hocko <mhocko@xxxxxxxx> Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> --- include/linux/memcontrol.h | 6 +- include/linux/mmzone.h | 11 +++- mm/vmscan.c | 84 ++++++++++------------------------- 3 files changed, 37 insertions(+), 64 deletions(-) --- a/include/linux/memcontrol.h~mm-vmscan-harmonize-writeback-congestion-tracking-for-nodes-memcgs +++ a/include/linux/memcontrol.h @@ -132,9 +132,6 @@ struct mem_cgroup_per_node { unsigned long usage_in_excess;/* Set to the value by which */ /* the soft limit is exceeded*/ bool on_tree; - bool congested; /* memcg has many dirty pages */ - /* backed by a congested BDI */ - struct mem_cgroup *memcg; /* Back pointer, we cannot */ /* use container_of */ }; @@ -403,6 +400,9 @@ static inline struct lruvec *mem_cgroup_ goto out; } + if (!memcg) + memcg = root_mem_cgroup; + mz = mem_cgroup_nodeinfo(memcg, pgdat->node_id); lruvec = &mz->lruvec; out: --- a/include/linux/mmzone.h~mm-vmscan-harmonize-writeback-congestion-tracking-for-nodes-memcgs +++ a/include/linux/mmzone.h @@ -296,6 +296,12 @@ struct zone_reclaim_stat { unsigned long recent_scanned[2]; }; +enum lruvec_flags { + LRUVEC_CONGESTED, /* lruvec has many dirty pages + * backed by a congested BDI + */ +}; + struct lruvec { struct list_head lists[NR_LRU_LISTS]; struct zone_reclaim_stat reclaim_stat; @@ -303,6 +309,8 @@ struct lruvec { atomic_long_t inactive_age; /* Refaults at the time of last reclaim cycle */ unsigned long refaults; + /* Various lruvec state flags (enum lruvec_flags) */ + unsigned long flags; #ifdef CONFIG_MEMCG struct pglist_data *pgdat; #endif @@ -572,9 +580,6 @@ struct zone { } ____cacheline_internodealigned_in_smp; enum pgdat_flags { - PGDAT_CONGESTED, /* pgdat has many dirty pages backed by - * a congested BDI - */ PGDAT_DIRTY, /* reclaim scanning has recently found * many dirty file pages at the tail * of the LRU. --- a/mm/vmscan.c~mm-vmscan-harmonize-writeback-congestion-tracking-for-nodes-memcgs +++ a/mm/vmscan.c @@ -267,29 +267,6 @@ static bool writeback_throttling_sane(st #endif return false; } - -static void set_memcg_congestion(pg_data_t *pgdat, - struct mem_cgroup *memcg, - bool congested) -{ - struct mem_cgroup_per_node *mn; - - if (!memcg) - return; - - mn = mem_cgroup_nodeinfo(memcg, pgdat->node_id); - WRITE_ONCE(mn->congested, congested); -} - -static bool memcg_congested(pg_data_t *pgdat, - struct mem_cgroup *memcg) -{ - struct mem_cgroup_per_node *mn; - - mn = mem_cgroup_nodeinfo(memcg, pgdat->node_id); - return READ_ONCE(mn->congested); - -} #else static int prealloc_memcg_shrinker(struct shrinker *shrinker) { @@ -309,18 +286,6 @@ static bool writeback_throttling_sane(st { return true; } - -static inline void set_memcg_congestion(struct pglist_data *pgdat, - struct mem_cgroup *memcg, bool congested) -{ -} - -static inline bool memcg_congested(struct pglist_data *pgdat, - struct mem_cgroup *memcg) -{ - return false; - -} #endif /* @@ -2716,12 +2681,6 @@ static inline bool should_continue_recla return inactive_lru_pages > pages_for_compaction; } -static bool pgdat_memcg_congested(pg_data_t *pgdat, struct mem_cgroup *memcg) -{ - return test_bit(PGDAT_CONGESTED, &pgdat->flags) || - (memcg && memcg_congested(pgdat, memcg)); -} - static void shrink_node_memcgs(pg_data_t *pgdat, struct scan_control *sc) { struct mem_cgroup *target_memcg = sc->target_mem_cgroup; @@ -2783,10 +2742,12 @@ static void shrink_node_memcgs(pg_data_t static bool shrink_node(pg_data_t *pgdat, struct scan_control *sc) { struct reclaim_state *reclaim_state = current->reclaim_state; - struct mem_cgroup *target_memcg = sc->target_mem_cgroup; unsigned long nr_reclaimed, nr_scanned; + struct lruvec *target_lruvec; bool reclaimable = false; + target_lruvec = mem_cgroup_lruvec(sc->target_mem_cgroup, pgdat); + again: memset(&sc->nr, 0, sizeof(sc->nr)); @@ -2801,7 +2762,7 @@ again: } /* Record the subtree's reclaim efficiency */ - vmpressure(sc->gfp_mask, target_memcg, true, + vmpressure(sc->gfp_mask, sc->target_mem_cgroup, true, sc->nr_scanned - nr_scanned, sc->nr_reclaimed - nr_reclaimed); @@ -2829,14 +2790,6 @@ again: if (sc->nr.writeback && sc->nr.writeback == sc->nr.taken) set_bit(PGDAT_WRITEBACK, &pgdat->flags); - /* - * Tag a node as congested if all the dirty pages - * scanned were backed by a congested BDI and - * wait_iff_congested will stall. - */ - if (sc->nr.dirty && sc->nr.dirty == sc->nr.congested) - set_bit(PGDAT_CONGESTED, &pgdat->flags); - /* Allow kswapd to start writing pages during reclaim.*/ if (sc->nr.unqueued_dirty == sc->nr.file_taken) set_bit(PGDAT_DIRTY, &pgdat->flags); @@ -2852,12 +2805,17 @@ again: } /* + * Tag a node/memcg as congested if all the dirty pages + * scanned were backed by a congested BDI and + * wait_iff_congested will stall. + * * Legacy memcg will stall in page writeback so avoid forcibly * stalling in wait_iff_congested(). */ - if (cgroup_reclaim(sc) && writeback_throttling_sane(sc) && + if ((current_is_kswapd() || + (cgroup_reclaim(sc) && writeback_throttling_sane(sc))) && sc->nr.dirty && sc->nr.dirty == sc->nr.congested) - set_memcg_congestion(pgdat, target_memcg, true); + set_bit(LRUVEC_CONGESTED, &target_lruvec->flags); /* * Stall direct reclaim for IO completions if underlying BDIs @@ -2865,9 +2823,9 @@ again: * starts encountering unqueued dirty pages or cycling through * the LRU too quickly. */ - if (!sc->hibernation_mode && !current_is_kswapd() && - current_may_throttle() && - pgdat_memcg_congested(pgdat, target_memcg)) + if (!current_is_kswapd() && current_may_throttle() && + !sc->hibernation_mode && + test_bit(LRUVEC_CONGESTED, &target_lruvec->flags)) wait_iff_congested(BLK_RW_ASYNC, HZ/10); if (should_continue_reclaim(pgdat, sc->nr_reclaimed - nr_reclaimed, @@ -3081,8 +3039,16 @@ retry: if (zone->zone_pgdat == last_pgdat) continue; last_pgdat = zone->zone_pgdat; + snapshot_refaults(sc->target_mem_cgroup, zone->zone_pgdat); - set_memcg_congestion(last_pgdat, sc->target_mem_cgroup, false); + + if (cgroup_reclaim(sc)) { + struct lruvec *lruvec; + + lruvec = mem_cgroup_lruvec(sc->target_mem_cgroup, + zone->zone_pgdat); + clear_bit(LRUVEC_CONGESTED, &lruvec->flags); + } } delayacct_freepages_end(); @@ -3450,7 +3416,9 @@ static bool pgdat_balanced(pg_data_t *pg /* Clear pgdat state for congested, dirty or under writeback. */ static void clear_pgdat_congested(pg_data_t *pgdat) { - clear_bit(PGDAT_CONGESTED, &pgdat->flags); + struct lruvec *lruvec = mem_cgroup_lruvec(NULL, pgdat); + + clear_bit(LRUVEC_CONGESTED, &lruvec->flags); clear_bit(PGDAT_DIRTY, &pgdat->flags); clear_bit(PGDAT_WRITEBACK, &pgdat->flags); } _
