From b2e18757f2c9d1cdd746a882e9878852fdec9501 Mon Sep 17 00:00:00 2001 From: Mel Gorman Date: Thu, 28 Jul 2016 15:45:37 -0700 Subject: [PATCH] mm, vmscan: begin reclaiming pages on a per-node basis This patch makes reclaim decisions on a per-node basis. A reclaimer knows what zone is required by the allocation request and skips pages from higher zones. In many cases this will be ok because it's a GFP_HIGHMEM request of some description. On 64-bit, ZONE_DMA32 requests will cause some problems but 32-bit devices on 64-bit platforms are increasingly rare. Historically it would have been a major problem on 32-bit with big Highmem:Lowmem ratios but such configurations are also now rare and even where they exist, they are not encouraged. If it really becomes a problem, it'll manifest as very low reclaim efficiencies. Link: http://lkml.kernel.org/r/1467970510-21195-6-git-send-email-mgorman@techsingularity.net Signed-off-by: Mel Gorman Acked-by: Hillf Danton Acked-by: Johannes Weiner Acked-by: Vlastimil Babka Cc: Joonsoo Kim Cc: Michal Hocko Cc: Minchan Kim Cc: Rik van Riel Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- mm/vmscan.c | 79 ++++++++++++++++++++++++++++++++++++++++++------------------- 1 file changed, 55 insertions(+), 24 deletions(-) diff --git a/mm/vmscan.c b/mm/vmscan.c index 86a523a..766b36b 100644 --- a/mm/vmscan.c +++ b/mm/vmscan.c @@ -84,6 +84,9 @@ struct scan_control { /* Scan (total_size >> priority) pages at once */ int priority; + /* The highest zone to isolate pages for reclaim from */ + enum zone_type reclaim_idx; + unsigned int may_writepage:1; /* Can mapped pages be reclaimed? */ @@ -1392,6 +1395,7 @@ static unsigned long isolate_lru_pages(unsigned long nr_to_scan, unsigned long nr_taken = 0; unsigned long nr_zone_taken[MAX_NR_ZONES] = { 0 }; unsigned long scan, nr_pages; + LIST_HEAD(pages_skipped); for (scan = 0; scan < nr_to_scan && nr_taken < nr_to_scan && !list_empty(src); scan++) { @@ -1402,6 +1406,11 @@ static unsigned long isolate_lru_pages(unsigned long nr_to_scan, VM_BUG_ON_PAGE(!PageLRU(page), page); + if (page_zonenum(page) > sc->reclaim_idx) { + list_move(&page->lru, &pages_skipped); + continue; + } + switch (__isolate_lru_page(page, mode)) { case 0: nr_pages = hpage_nr_pages(page); @@ -1420,6 +1429,15 @@ static unsigned long isolate_lru_pages(unsigned long nr_to_scan, } } + /* + * Splice any skipped pages to the start of the LRU list. Note that + * this disrupts the LRU order when reclaiming for lower zones but + * we cannot splice to the tail. If we did then the SWAP_CLUSTER_MAX + * scanning would soon rescan the same pages to skip and put the + * system at risk of premature OOM. + */ + if (!list_empty(&pages_skipped)) + list_splice(&pages_skipped, src); *nr_scanned = scan; trace_mm_vmscan_lru_isolate(sc->order, nr_to_scan, scan, nr_taken, mode, is_file_lru(lru)); @@ -1589,7 +1607,7 @@ static int current_may_throttle(void) } /* - * shrink_inactive_list() is a helper for shrink_zone(). It returns the number + * shrink_inactive_list() is a helper for shrink_node(). It returns the number * of reclaimed pages */ static noinline_for_stack unsigned long @@ -2401,12 +2419,13 @@ static inline bool should_continue_reclaim(struct zone *zone, } } -static bool shrink_zone(struct zone *zone, struct scan_control *sc, - bool is_classzone) +static bool shrink_node(pg_data_t *pgdat, struct scan_control *sc, + enum zone_type classzone_idx) { struct reclaim_state *reclaim_state = current->reclaim_state; unsigned long nr_reclaimed, nr_scanned; bool reclaimable = false; + struct zone *zone = &pgdat->node_zones[classzone_idx]; do { struct mem_cgroup *root = sc->target_mem_cgroup; @@ -2438,7 +2457,7 @@ static bool shrink_zone(struct zone *zone, struct scan_control *sc, shrink_zone_memcg(zone, memcg, sc, &lru_pages); zone_lru_pages += lru_pages; - if (memcg && is_classzone) + if (!global_reclaim(sc)) shrink_slab(sc->gfp_mask, zone_to_nid(zone), memcg, sc->nr_scanned - scanned, lru_pages); @@ -2469,7 +2488,7 @@ static bool shrink_zone(struct zone *zone, struct scan_control *sc, * Shrink the slab caches in the same proportion that * the eligible LRU pages were scanned. */ - if (global_reclaim(sc) && is_classzone) + if (global_reclaim(sc)) shrink_slab(sc->gfp_mask, zone_to_nid(zone), NULL, sc->nr_scanned - nr_scanned, zone_lru_pages); @@ -2553,7 +2572,7 @@ static void shrink_zones(struct zonelist *zonelist, struct scan_control *sc) unsigned long nr_soft_reclaimed; unsigned long nr_soft_scanned; gfp_t orig_mask; - enum zone_type requested_highidx = gfp_zone(sc->gfp_mask); + enum zone_type classzone_idx; /* * If the number of buffer_heads in the machine exceeds the maximum @@ -2561,17 +2580,23 @@ static void shrink_zones(struct zonelist *zonelist, struct scan_control *sc) * highmem pages could be pinning lowmem pages storing buffer_heads */ orig_mask = sc->gfp_mask; - if (buffer_heads_over_limit) + if (buffer_heads_over_limit) { sc->gfp_mask |= __GFP_HIGHMEM; + sc->reclaim_idx = classzone_idx = gfp_zone(sc->gfp_mask); + } for_each_zone_zonelist_nodemask(zone, z, zonelist, - gfp_zone(sc->gfp_mask), sc->nodemask) { - enum zone_type classzone_idx; - + sc->reclaim_idx, sc->nodemask) { if (!populated_zone(zone)) continue; - classzone_idx = requested_highidx; + /* + * Note that reclaim_idx does not change as it is the highest + * zone reclaimed from which for empty zones is a no-op but + * classzone_idx is used by shrink_node to test if the slabs + * should be shrunk on a given node. + */ + classzone_idx = sc->reclaim_idx; while (!populated_zone(zone->zone_pgdat->node_zones + classzone_idx)) classzone_idx--; @@ -2600,8 +2625,8 @@ static void shrink_zones(struct zonelist *zonelist, struct scan_control *sc) */ if (IS_ENABLED(CONFIG_COMPACTION) && sc->order > PAGE_ALLOC_COSTLY_ORDER && - zonelist_zone_idx(z) <= requested_highidx && - compaction_ready(zone, sc->order, requested_highidx)) { + zonelist_zone_idx(z) <= classzone_idx && + compaction_ready(zone, sc->order, classzone_idx)) { sc->compaction_ready = true; continue; } @@ -2621,7 +2646,7 @@ static void shrink_zones(struct zonelist *zonelist, struct scan_control *sc) /* need some check for avoid more shrink_zone() */ } - shrink_zone(zone, sc, zone_idx(zone) == classzone_idx); + shrink_node(zone->zone_pgdat, sc, classzone_idx); } /* @@ -2847,6 +2872,7 @@ unsigned long try_to_free_pages(struct zonelist *zonelist, int order, struct scan_control sc = { .nr_to_reclaim = SWAP_CLUSTER_MAX, .gfp_mask = (gfp_mask = memalloc_noio_flags(gfp_mask)), + .reclaim_idx = gfp_zone(gfp_mask), .order = order, .nodemask = nodemask, .priority = DEF_PRIORITY, @@ -2886,6 +2912,7 @@ unsigned long mem_cgroup_shrink_node_zone(struct mem_cgroup *memcg, .target_mem_cgroup = memcg, .may_writepage = !laptop_mode, .may_unmap = 1, + .reclaim_idx = MAX_NR_ZONES - 1, .may_swap = !noswap, }; unsigned long lru_pages; @@ -2924,6 +2951,7 @@ unsigned long try_to_free_mem_cgroup_pages(struct mem_cgroup *memcg, .nr_to_reclaim = max(nr_pages, SWAP_CLUSTER_MAX), .gfp_mask = (gfp_mask & GFP_RECLAIM_MASK) | (GFP_HIGHUSER_MOVABLE & ~GFP_RECLAIM_MASK), + .reclaim_idx = MAX_NR_ZONES - 1, .target_mem_cgroup = memcg, .priority = DEF_PRIORITY, .may_writepage = !laptop_mode, @@ -3118,7 +3146,7 @@ static bool kswapd_shrink_zone(struct zone *zone, balance_gap, classzone_idx)) return true; - shrink_zone(zone, sc, zone_idx(zone) == classzone_idx); + shrink_node(zone->zone_pgdat, sc, classzone_idx); /* TODO: ANOMALY */ clear_bit(PGDAT_WRITEBACK, &pgdat->flags); @@ -3167,6 +3195,7 @@ static int balance_pgdat(pg_data_t *pgdat, int order, int classzone_idx) unsigned long nr_soft_scanned; struct scan_control sc = { .gfp_mask = GFP_KERNEL, + .reclaim_idx = MAX_NR_ZONES - 1, .order = order, .priority = DEF_PRIORITY, .may_writepage = !laptop_mode, @@ -3237,15 +3266,14 @@ static int balance_pgdat(pg_data_t *pgdat, int order, int classzone_idx) sc.may_writepage = 1; /* - * Now scan the zone in the dma->highmem direction, stopping - * at the last zone which needs scanning. - * - * We do this because the page allocator works in the opposite - * direction. This prevents the page allocator from allocating - * pages behind kswapd's direction of progress, which would - * cause too much scanning of the lower zones. + * Continue scanning in the highmem->dma direction stopping at + * the last zone which needs scanning. This may reclaim lowmem + * pages that are not necessary for zone balancing but it + * preserves LRU ordering. It is assumed that the bulk of + * allocation requests can use arbitrary zones with the + * possible exception of big highmem:lowmem configurations. */ - for (i = 0; i <= end_zone; i++) { + for (i = end_zone; i >= 0; i--) { struct zone *zone = pgdat->node_zones + i; if (!populated_zone(zone)) @@ -3256,6 +3284,7 @@ static int balance_pgdat(pg_data_t *pgdat, int order, int classzone_idx) continue; sc.nr_scanned = 0; + sc.reclaim_idx = i; nr_soft_scanned = 0; /* @@ -3513,6 +3542,7 @@ unsigned long shrink_all_memory(unsigned long nr_to_reclaim) struct scan_control sc = { .nr_to_reclaim = nr_to_reclaim, .gfp_mask = GFP_HIGHUSER_MOVABLE, + .reclaim_idx = MAX_NR_ZONES - 1, .priority = DEF_PRIORITY, .may_writepage = 1, .may_unmap = 1, @@ -3704,6 +3734,7 @@ static int __zone_reclaim(struct zone *zone, gfp_t gfp_mask, unsigned int order) .may_writepage = !!(zone_reclaim_mode & RECLAIM_WRITE), .may_unmap = !!(zone_reclaim_mode & RECLAIM_UNMAP), .may_swap = 1, + .reclaim_idx = zone_idx(zone), }; cond_resched(); @@ -3723,7 +3754,7 @@ static int __zone_reclaim(struct zone *zone, gfp_t gfp_mask, unsigned int order) * priorities until we have enough memory freed. */ do { - shrink_zone(zone, &sc, true); + shrink_node(zone->zone_pgdat, &sc, zone_idx(zone)); } while (sc.nr_reclaimed < nr_pages && --sc.priority >= 0); } -- 2.7.4