Hi, Michal and all I'm so sorry, now I updated the review list. Thank you all for the review and comments! In this version: Remove change ID according to Minchan's comment; Reorder the check in shrink_zones according Johannes's comment. Also cc to more people. >From ff345123117394c6b9b838bf54eb935bfa879f32 Mon Sep 17 00:00:00 2001 From: Lisa Du <cldu@xxxxxxxxxxx> Date: Mon, 5 Aug 2013 09:26:57 +0800 Subject: [PATCH] mm: vmscan: fix do_try_to_free_pages() livelock This patch is based on KOSAKI's work and I add a little more description, please refer https://lkml.org/lkml/2012/6/14/74. Currently, I found system can enter a state that there are lots of free pages in a zone but only order-0 and order-1 pages which means the zone is heavily fragmented, then high order allocation could make direct reclaim path's long stall(ex, 60 seconds) especially in no swap and no compaciton enviroment. This problem happened on v3.4, but it seems issue still lives in current tree, the reason is do_try_to_free_pages enter live lock: kswapd will go to sleep if the zones have been fully scanned and are still not balanced. As kswapd thinks there's little point trying all over again to avoid infinite loop. Instead it changes order from high-order to 0-order because kswapd think order-0 is the most important. Look at 73ce02e9 in detail. If watermarks are ok, kswapd will go back to sleep and may leave zone->all_unreclaimable = 0. It assume high-order users can still perform direct reclaim if they wish. Direct reclaim continue to reclaim for a high order which is not a COSTLY_ORDER without oom-killer until kswapd turn on zone->all_unreclaimble. This is because to avoid too early oom-kill. So it means direct_reclaim depends on kswapd to break this loop. In worst case, direct-reclaim may continue to page reclaim forever when kswapd sleeps forever until someone like watchdog detect and finally kill the process. As described in: http://thread.gmane.org/gmane.linux.kernel.mm/103737 We can't turn on zone->all_unreclaimable from direct reclaim path because direct reclaim path don't take any lock and this way is racy. Thus this patch removes zone->all_unreclaimable field completely and recalculates zone reclaimable state every time. Note: we can't take the idea that direct-reclaim see zone->pages_scanned directly and kswapd continue to use zone->all_unreclaimable. Because, it is racy. commit 929bea7c71 (vmscan: all_unreclaimable() use zone->all_unreclaimable as a name) describes the detail. Cc: Aaditya Kumar <aaditya.kumar.30@xxxxxxxxx> Cc: Ying Han <yinghan@xxxxxxxxxx> Cc: Nick Piggin <npiggin@xxxxxxxxx> Acked-by: Rik van Riel <riel@xxxxxxxxxx> Cc: Mel Gorman <mel@xxxxxxxxx> Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@xxxxxxxxxxxxxx> Cc: Christoph Lameter <cl@xxxxxxxxx> Cc: Bob Liu <lliubbo@xxxxxxxxx> Cc: Neil Zhang <zhangwm@xxxxxxxxxxx> Cc: Russell King - ARM Linux <linux@xxxxxxxxxxxxxxxx> Acked-by: Minchan Kim <minchan@xxxxxxxxxx> Reviewed-by: Michal Hocko <mhocko@xxxxxxx> Reviewed-by: Johannes Weiner <hannes@xxxxxxxxxxx> Signed-off-by: KOSAKI Motohiro <kosaki.motohiro@xxxxxxxxxxxxxx> Signed-off-by: Lisa Du <cldu@xxxxxxxxxxx> --- include/linux/mm_inline.h | 20 ++++++++++++++++++++ include/linux/mmzone.h | 1 - include/linux/vmstat.h | 1 - mm/page-writeback.c | 1 + mm/page_alloc.c | 5 ++--- mm/vmscan.c | 43 ++++++++++--------------------------------- mm/vmstat.c | 3 ++- 7 files changed, 35 insertions(+), 39 deletions(-) diff --git a/include/linux/mm_inline.h b/include/linux/mm_inline.h index 1397ccf..e212fae 100644 --- a/include/linux/mm_inline.h +++ b/include/linux/mm_inline.h @@ -2,6 +2,7 @@ #define LINUX_MM_INLINE_H #include <linux/huge_mm.h> +#include <linux/swap.h> /** * page_is_file_cache - should the page be on a file LRU or anon LRU? @@ -99,4 +100,23 @@ static __always_inline enum lru_list page_lru(struct page *page) return lru; } +static inline unsigned long zone_reclaimable_pages(struct zone *zone) +{ + int nr; + + nr = zone_page_state(zone, NR_ACTIVE_FILE) + + zone_page_state(zone, NR_INACTIVE_FILE); + + if (get_nr_swap_pages() > 0) + nr += zone_page_state(zone, NR_ACTIVE_ANON) + + zone_page_state(zone, NR_INACTIVE_ANON); + + return nr; +} + +static inline bool zone_reclaimable(struct zone *zone) +{ + return zone->pages_scanned < zone_reclaimable_pages(zone) * 6; +} + #endif diff --git a/include/linux/mmzone.h b/include/linux/mmzone.h index af4a3b7..e835974 100644 --- a/include/linux/mmzone.h +++ b/include/linux/mmzone.h @@ -352,7 +352,6 @@ struct zone { * free areas of different sizes */ spinlock_t lock; - int all_unreclaimable; /* All pages pinned */ #if defined CONFIG_COMPACTION || defined CONFIG_CMA /* Set to true when the PG_migrate_skip bits should be cleared */ bool compact_blockskip_flush; diff --git a/include/linux/vmstat.h b/include/linux/vmstat.h index c586679..6fff004 100644 --- a/include/linux/vmstat.h +++ b/include/linux/vmstat.h @@ -143,7 +143,6 @@ static inline unsigned long zone_page_state_snapshot(struct zone *zone, } extern unsigned long global_reclaimable_pages(void); -extern unsigned long zone_reclaimable_pages(struct zone *zone); #ifdef CONFIG_NUMA /* diff --git a/mm/page-writeback.c b/mm/page-writeback.c index 3f0c895..62bfd92 100644 --- a/mm/page-writeback.c +++ b/mm/page-writeback.c @@ -36,6 +36,7 @@ #include <linux/pagevec.h> #include <linux/timer.h> #include <linux/sched/rt.h> +#include <linux/mm_inline.h> #include <trace/events/writeback.h> /* diff --git a/mm/page_alloc.c b/mm/page_alloc.c index b100255..19a18c0 100644 --- a/mm/page_alloc.c +++ b/mm/page_alloc.c @@ -60,6 +60,7 @@ #include <linux/page-debug-flags.h> #include <linux/hugetlb.h> #include <linux/sched/rt.h> +#include <linux/mm_inline.h> #include <asm/sections.h> #include <asm/tlbflush.h> @@ -647,7 +648,6 @@ static void free_pcppages_bulk(struct zone *zone, int count, int to_free = count; spin_lock(&zone->lock); - zone->all_unreclaimable = 0; zone->pages_scanned = 0; while (to_free) { @@ -696,7 +696,6 @@ static void free_one_page(struct zone *zone, struct page *page, int order, int migratetype) { spin_lock(&zone->lock); - zone->all_unreclaimable = 0; zone->pages_scanned = 0; __free_one_page(page, zone, order, migratetype); @@ -3095,7 +3094,7 @@ void show_free_areas(unsigned int filter) K(zone_page_state(zone, NR_FREE_CMA_PAGES)), K(zone_page_state(zone, NR_WRITEBACK_TEMP)), zone->pages_scanned, - (zone->all_unreclaimable ? "yes" : "no") + (!zone_reclaimable(zone) ? "yes" : "no") ); printk("lowmem_reserve[]:"); for (i = 0; i < MAX_NR_ZONES; i++) diff --git a/mm/vmscan.c b/mm/vmscan.c index 2cff0d4..e1a48d4 100644 --- a/mm/vmscan.c +++ b/mm/vmscan.c @@ -1789,7 +1789,7 @@ static void get_scan_count(struct lruvec *lruvec, struct scan_control *sc, * latencies, so it's better to scan a minimum amount there as * well. */ - if (current_is_kswapd() && zone->all_unreclaimable) + if (current_is_kswapd() && !zone_reclaimable(zone)) force_scan = true; if (!global_reclaim(sc)) force_scan = true; @@ -2244,8 +2244,8 @@ static bool shrink_zones(struct zonelist *zonelist, struct scan_control *sc) if (global_reclaim(sc)) { if (!cpuset_zone_allowed_hardwall(zone, GFP_KERNEL)) continue; - if (zone->all_unreclaimable && - sc->priority != DEF_PRIORITY) + if (sc->priority != DEF_PRIORITY && + !zone_reclaimable(zone)) continue; /* Let kswapd poll it */ if (IS_ENABLED(CONFIG_COMPACTION)) { /* @@ -2283,11 +2283,6 @@ static bool shrink_zones(struct zonelist *zonelist, struct scan_control *sc) return aborted_reclaim; } -static bool zone_reclaimable(struct zone *zone) -{ - return zone->pages_scanned < zone_reclaimable_pages(zone) * 6; -} - /* All zones in zonelist are unreclaimable? */ static bool all_unreclaimable(struct zonelist *zonelist, struct scan_control *sc) @@ -2301,7 +2296,7 @@ static bool all_unreclaimable(struct zonelist *zonelist, continue; if (!cpuset_zone_allowed_hardwall(zone, GFP_KERNEL)) continue; - if (!zone->all_unreclaimable) + if (zone_reclaimable(zone)) return false; } @@ -2712,7 +2707,7 @@ static bool pgdat_balanced(pg_data_t *pgdat, int order, int classzone_idx) * DEF_PRIORITY. Effectively, it considers them balanced so * they must be considered balanced here as well! */ - if (zone->all_unreclaimable) { + if (!zone_reclaimable(zone)) { balanced_pages += zone->managed_pages; continue; } @@ -2773,7 +2768,6 @@ static bool kswapd_shrink_zone(struct zone *zone, unsigned long lru_pages, unsigned long *nr_attempted) { - unsigned long nr_slab; int testorder = sc->order; unsigned long balance_gap; struct reclaim_state *reclaim_state = current->reclaim_state; @@ -2818,15 +2812,12 @@ static bool kswapd_shrink_zone(struct zone *zone, shrink_zone(zone, sc); reclaim_state->reclaimed_slab = 0; - nr_slab = shrink_slab(&shrink, sc->nr_scanned, lru_pages); + shrink_slab(&shrink, sc->nr_scanned, lru_pages); sc->nr_reclaimed += reclaim_state->reclaimed_slab; /* Account for the number of pages attempted to reclaim */ *nr_attempted += sc->nr_to_reclaim; - if (nr_slab == 0 && !zone_reclaimable(zone)) - zone->all_unreclaimable = 1; - zone_clear_flag(zone, ZONE_WRITEBACK); /* @@ -2835,7 +2826,7 @@ static bool kswapd_shrink_zone(struct zone *zone, * BDIs but as pressure is relieved, speculatively avoid congestion * waits. */ - if (!zone->all_unreclaimable && + if (zone_reclaimable(zone) && zone_balanced(zone, testorder, 0, classzone_idx)) { zone_clear_flag(zone, ZONE_CONGESTED); zone_clear_flag(zone, ZONE_TAIL_LRU_DIRTY); @@ -2901,7 +2892,7 @@ static unsigned long balance_pgdat(pg_data_t *pgdat, int order, if (!populated_zone(zone)) continue; - if (zone->all_unreclaimable && + if (!zone_reclaimable(zone) && sc.priority != DEF_PRIORITY) continue; @@ -2980,7 +2971,7 @@ static unsigned long balance_pgdat(pg_data_t *pgdat, int order, if (!populated_zone(zone)) continue; - if (zone->all_unreclaimable && + if (!zone_reclaimable(zone) && sc.priority != DEF_PRIORITY) continue; @@ -3265,20 +3256,6 @@ unsigned long global_reclaimable_pages(void) return nr; } -unsigned long zone_reclaimable_pages(struct zone *zone) -{ - int nr; - - nr = zone_page_state(zone, NR_ACTIVE_FILE) + - zone_page_state(zone, NR_INACTIVE_FILE); - - if (get_nr_swap_pages() > 0) - nr += zone_page_state(zone, NR_ACTIVE_ANON) + - zone_page_state(zone, NR_INACTIVE_ANON); - - return nr; -} - #ifdef CONFIG_HIBERNATION /* * Try to free `nr_to_reclaim' of memory, system-wide, and return the number of @@ -3576,7 +3553,7 @@ int zone_reclaim(struct zone *zone, gfp_t gfp_mask, unsigned int order) zone_page_state(zone, NR_SLAB_RECLAIMABLE) <= zone->min_slab_pages) return ZONE_RECLAIM_FULL; - if (zone->all_unreclaimable) + if (!zone_reclaimable(zone)) return ZONE_RECLAIM_FULL; /* diff --git a/mm/vmstat.c b/mm/vmstat.c index 20c2ef4..c48f75b 100644 --- a/mm/vmstat.c +++ b/mm/vmstat.c @@ -19,6 +19,7 @@ #include <linux/math64.h> #include <linux/writeback.h> #include <linux/compaction.h> +#include <linux/mm_inline.h> #ifdef CONFIG_VM_EVENT_COUNTERS DEFINE_PER_CPU(struct vm_event_state, vm_event_states) = {{0}}; @@ -1052,7 +1053,7 @@ static void zoneinfo_show_print(struct seq_file *m, pg_data_t *pgdat, "\n all_unreclaimable: %u" "\n start_pfn: %lu" "\n inactive_ratio: %u", - zone->all_unreclaimable, + !zone_reclaimable(zone), zone->zone_start_pfn, zone->inactive_ratio); seq_putc(m, '\n'); -- 1.7.0.4 Thanks! Best Regards Lisa Du -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href