From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754038AbcDOJOf (ORCPT ); Fri, 15 Apr 2016 05:14:35 -0400 Received: from outbound-smtp11.blacknight.com ([46.22.139.16]:49705 "EHLO outbound-smtp11.blacknight.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753820AbcDOJO1 (ORCPT ); Fri, 15 Apr 2016 05:14:27 -0400 From: Mel Gorman To: Andrew Morton , Linux-MM Cc: Rik van Riel , Vlastimil Babka , Johannes Weiner , Jesper Dangaard Brouer , LKML , Mel Gorman Subject: [PATCH 04/27] mm, vmscan: Begin reclaiming pages on a per-node basis Date: Fri, 15 Apr 2016 10:13:10 +0100 Message-Id: <1460711613-2761-5-git-send-email-mgorman@techsingularity.net> X-Mailer: git-send-email 2.6.4 In-Reply-To: <1460711613-2761-1-git-send-email-mgorman@techsingularity.net> References: <1460711613-2761-1-git-send-email-mgorman@techsingularity.net> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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. Signed-off-by: Mel Gorman --- mm/vmscan.c | 77 ++++++++++++++++++++++++++++++++++++++----------------------- 1 file changed, 48 insertions(+), 29 deletions(-) diff --git a/mm/vmscan.c b/mm/vmscan.c index 75acb89c9df5..0f8dc3488f9d 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? */ @@ -1369,6 +1372,7 @@ static unsigned long isolate_lru_pages(unsigned long nr_to_scan, struct list_head *src = &lruvec->lists[lru]; unsigned long nr_taken = 0; unsigned long scan; + LIST_HEAD(pages_skipped); for (scan = 0; scan < nr_to_scan && nr_taken < nr_to_scan && !list_empty(src); scan++) { @@ -1380,6 +1384,11 @@ 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); @@ -1398,6 +1407,15 @@ 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)); @@ -1560,7 +1578,7 @@ 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 @@ -2394,12 +2412,13 @@ 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; @@ -2431,7 +2450,7 @@ 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) && sc->reclaim_idx == classzone_idx) shrink_slab(sc->gfp_mask, zone_to_nid(zone), memcg, sc->nr_scanned - scanned, lru_pages); @@ -2462,7 +2481,7 @@ 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) && sc->reclaim_idx == classzone_idx) shrink_slab(sc->gfp_mask, zone_to_nid(zone), NULL, sc->nr_scanned - nr_scanned, zone_lru_pages); @@ -2541,14 +2560,14 @@ static inline bool compaction_ready(struct zone *zone, int order) * * Returns true if a zone was reclaimable. */ -static bool shrink_zones(struct zonelist *zonelist, struct scan_control *sc) +static bool shrink_zones(struct zonelist *zonelist, struct scan_control *sc, + enum zone_type classzone_idx) { struct zoneref *z; struct zone *zone; unsigned long nr_soft_reclaimed; unsigned long nr_soft_scanned; gfp_t orig_mask; - enum zone_type requested_highidx = gfp_zone(sc->gfp_mask); bool reclaimable = false; /* @@ -2561,16 +2580,12 @@ static bool shrink_zones(struct zonelist *zonelist, struct scan_control *sc) sc->gfp_mask |= __GFP_HIGHMEM; for_each_zone_zonelist_nodemask(zone, z, zonelist, - requested_highidx, sc->nodemask) { - enum zone_type classzone_idx; - - if (!populated_zone(zone)) - continue; - - classzone_idx = requested_highidx; - while (!populated_zone(zone->zone_pgdat->node_zones + - classzone_idx)) + classzone_idx, sc->nodemask) { + if (!populated_zone(zone)) { + sc->reclaim_idx--; classzone_idx--; + continue; + } /* * Take care memory controller reclaiming has small influence @@ -2596,7 +2611,7 @@ static bool 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 && + zonelist_zone_idx(z) <= classzone_idx && compaction_ready(zone, sc->order)) { sc->compaction_ready = true; continue; @@ -2619,7 +2634,7 @@ static bool shrink_zones(struct zonelist *zonelist, struct scan_control *sc) /* need some check for avoid more shrink_zone() */ } - if (shrink_zone(zone, sc, zone_idx(zone) == classzone_idx)) + if (shrink_node(zone->zone_pgdat, sc, classzone_idx)) reclaimable = true; if (global_reclaim(sc) && @@ -2659,6 +2674,7 @@ static unsigned long do_try_to_free_pages(struct zonelist *zonelist, unsigned long total_scanned = 0; unsigned long writeback_threshold; bool zones_reclaimable; + enum zone_type classzone_idx = gfp_zone(sc->gfp_mask); retry: delayacct_freepages_start(); @@ -2669,7 +2685,8 @@ static unsigned long do_try_to_free_pages(struct zonelist *zonelist, vmpressure_prio(sc->gfp_mask, sc->target_mem_cgroup, sc->priority); sc->nr_scanned = 0; - zones_reclaimable = shrink_zones(zonelist, sc); + sc->reclaim_idx = classzone_idx; + zones_reclaimable = shrink_zones(zonelist, sc, classzone_idx); total_scanned += sc->nr_scanned; if (sc->nr_reclaimed >= sc->nr_to_reclaim) @@ -3128,7 +3145,7 @@ 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); @@ -3177,6 +3194,7 @@ 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, @@ -3247,15 +3265,14 @@ 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 >= end_zone; i--) { struct zone *zone = pgdat->node_zones + i; if (!populated_zone(zone)) @@ -3266,6 +3283,7 @@ 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; /* @@ -3714,6 +3732,7 @@ 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(); @@ -3733,7 +3752,7 @@ 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); } -- 2.6.4