mm: vmscan: scan until it founds eligible pages
Subsystems (3)
PATCH v2 1/1 mm: vmscan: scan until it founds eligible pages
Although there are a ton of free swap and anonymous LRU page in elgible zones, OOM happened.
balloon invoked oom-killer: gfp_mask=0x17080c0(GFP_KERNEL_ACCOUNT|__GFP_ZERO|__GFP_NOTRACK), nodemask=(null), order=0, oom_score_adj=0
CPU: 7 PID: 1138 Comm: balloon Not tainted 4.11.0-rc6-mm1-zram-00289-ge228d67e9677-dirty #17 Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS Ubuntu-1.8.2-1ubuntu1 04/01/2014 Call Trace: dump_stack+0x65/0x87 dump_header.isra.19+0x8f/0x20f ? preempt_count_add+0x9e/0xb0 ? _raw_spin_unlock_irqrestore+0x24/0x40 oom_kill_process+0x21d/0x3f0 ? has_capability_noaudit+0x17/0x20 out_of_memory+0xd8/0x390 __alloc_pages_slowpath+0xbc1/0xc50 ? anon_vma_interval_tree_insert+0x84/0x90 __alloc_pages_nodemask+0x1a5/0x1c0 pte_alloc_one+0x20/0x50 __pte_alloc+0x1e/0x110 __handle_mm_fault+0x919/0x960 handle_mm_fault+0x77/0x120 __do_page_fault+0x27a/0x550 trace_do_page_fault+0x43/0x150 do_async_page_fault+0x2c/0x90 async_page_fault+0x28/0x30 RIP: 0033:0x7fc4636bacb8 RSP: 002b:00007fff97c9c4c0 EFLAGS: 00010202 RAX: 00007fc3e818d000 RBX: 00007fc4639f8760 RCX: 00007fc46372e9ca RDX: 0000000000101002 RSI: 0000000000101000 RDI: 0000000000000000 RBP: 0000000000100010 R08: 00000000ffffffff R09: 0000000000000000 R10: 0000000000000022 R11: 00000000000a3901 R12: 00007fc3e818d010 R13: 0000000000101000 R14: 00007fc4639f87b8 R15: 00007fc4639f87b8
Mem-Info:
active_anon:424716 inactive_anon:65314 isolated_anon:0
active_file:52 inactive_file:46 isolated_file:0
unevictable:0 dirty:27 writeback:0 unstable:0
slab_reclaimable:3967 slab_unreclaimable:4125
mapped:133 shmem:43 pagetables:1674 bounce:0
free:4637 free_pcp:225 free_cma:0
Node 0 active_anon:1698864kB inactive_anon:261256kB active_file:208kB inactive_file:184kB unevictable:0kB isolated(anon):0kB isolated(file):0kB mapped:532kB dirty:108kB writeback:0kB shmem:172kB writeback_tmp:0kB unstable:0kB all_unreclaimable? no
DMA free:7316kB min:32kB low:44kB high:56kB active_anon:8064kB inactive_anon:0kB active_file:0kB inactive_file:0kB unevictable:0kB writepending:0kB present:15992kB managed:15908kB mlocked:0kB slab_reclaimable:464kB slab_unreclaimable:40kB kernel_stack:0kB pagetables:24kB bounce:0kB free_pcp:0kB local_pcp:0kB free_cma:0kB lowmem_reserve[]: 0 992 992 1952
DMA32 free:9088kB min:2048kB low:3064kB high:4080kB active_anon:952176kB inactive_anon:0kB active_file:36kB inactive_file:0kB unevictable:0kB writepending:88kB present:1032192kB managed:1019388kB mlocked:0kB slab_reclaimable:13532kB slab_unreclaimable:16460kB kernel_stack:3552kB pagetables:6672kB bounce:0kB free_pcp:56kB local_pcp:24kB free_cma:0kB lowmem_reserve[]: 0 0 0 959
Movable free:3644kB min:1980kB low:2960kB high:3940kB active_anon:738560kB inactive_anon:261340kB active_file:188kB inactive_file:640kB unevictable:0kB writepending:20kB present:1048444kB managed:1010816kB mlocked:0kB slab_reclaimable:0kB slab_unreclaimable:0kB kernel_stack:0kB pagetables:0kB bounce:0kB free_pcp:832kB local_pcp:60kB free_cma:0kB lowmem_reserve[]: 0 0 0 0
DMA: 1*4kB (E) 0*8kB 18*16kB (E) 10*32kB (E) 10*64kB (E) 9*128kB (ME) 8*256kB (E) 2*512kB (E) 2*1024kB (E) 0*2048kB 0*4096kB = 7524kB
DMA32: 417*4kB (UMEH) 181*8kB (UMEH) 68*16kB (UMEH) 48*32kB (UMEH) 14*64kB (MH) 3*128kB (M) 1*256kB (H) 1*512kB (M) 2*1024kB (M) 0*2048kB 0*4096kB = 9836kB
Movable: 1*4kB (M) 1*8kB (M) 1*16kB (M) 1*32kB (M) 0*64kB 1*128kB (M) 2*256kB (M) 4*512kB (M) 1*1024kB (M) 0*2048kB 0*4096kB = 3772kB
378 total pagecache pages
17 pages in swap cache
Swap cache stats: add 17325, delete 17302, find 0/27
Free swap = 978940kB
Total swap = 1048572kB
524157 pages RAM
0 pages HighMem/MovableOnly
12629 pages reserved
0 pages cma reserved
0 pages hwpoisoned
[ pid ] uid tgid total_vm rss nr_ptes nr_pmds swapents oom_score_adj name
[ 433] 0 433 4904 5 14 3 82 0 upstart-udev-br [ 438] 0 438 12371 5 27 3 191 -1000 systemd-udevd
With investigation, skipping page of isolate_lru_pages makes reclaim void because it returns zero nr_taken easily so LRU shrinking is effectively nothing and just increases priority aggressively. Finally, OOM happens.
The problem is that get_scan_count determines nr_to_scan with eligible zones so although priority drops to zero, it couldn't reclaim any pages if the LRU contains mostly ineligible pages.
get_scan_count:
size = lruvec_lru_size(lruvec, lru, sc->reclaim_idx); size = size >> sc->priority;
Assumes sc->priority is 0 and LRU list is as follows.
N-N-N-N-H-H-H-H-H-H-H-H-H-H-H-H-H-H-H-H
(Ie, small eligible pages are in the head of LRU but others are
almost ineligible pages)
In that case, size becomes 4 so VM want to scan 4 pages but 4 pages from tail of the LRU are not eligible pages.
If get_scan_count counts skipped pages, it doesn't reclaim any pages remained after scanning 4 pages so it ends up OOM happening.
This patch makes isolate_lru_pages try to scan pages until it encounters eligible zones's pages.
---
* from v1
* put more words in description and code
* drop unncessary pages_skipped list flushing
mm/vmscan.c | 21 +++++++++++++++------ 1 file changed, 15 insertions(+), 6 deletions(-)
mm/vmscan.c +15 -6
@@ -1449,7 +1449,7 @@ static __always_inline void update_lru_sizes(struct lruvec *lruvec,* * Appropriate locks must be held before calling this function. * -* @nr_to_scan: The number of pages to look through on the list. +* @nr_to_scan: The number of eligible pages to look through on the list. * @lruvec: The LRU vector to pull pages from. * @dst: The temp list to put pages on to. * @nr_scanned: The number of pages that were scanned.
@@ -1469,11 +1469,13 @@ static unsigned long isolate_lru_pages(unsigned long nr_to_scan,unsigned long nr_zone_taken[MAX_NR_ZONES ] = {0 };unsigned long nr_skipped[MAX_NR_ZONES ] = {0 , };unsigned long skipped =0 ; -unsigned long scan, nr_pages; +unsigned long scan, total_scan, nr_pages;LIST_HEAD (pages_skipped); -for (scan =0 ; scan < nr_to_scan && nr_taken < nr_to_scan && - !list_empty (src); scan++) { +for (total_scan = scan =0 ; scan < nr_to_scan && + nr_taken < nr_to_scan && + !list_empty (src); + total_scan++) {struct page *page; page =lru_to_page (src);
@@ -1487,6 +1489,13 @@ static unsigned long isolate_lru_pages(unsigned long nr_to_scan,continue ; } +/* +* Do not count skipped pages because it makes the function to +* return with none isolated pages if the LRU mostly contains +* ineligible pages so that VM cannot reclaim any pages and +* trigger premature OOM. +*/ + scan++;switch (__isolate_lru_page (page, mode)) {case 0 : nr_pages =hpage_nr_pages (page);
@@ -1524,9 +1533,9 @@ static unsigned long isolate_lru_pages(unsigned long nr_to_scan, skipped += nr_skipped[zid]; } } - *nr_scanned = scan; + *nr_scanned = total_scan;trace_mm_vmscan_lru_isolate (sc->reclaim_idx, sc->order, nr_to_scan, - scan, skipped, nr_taken, mode, lru); + total_scan, skipped, nr_taken, mode, lru);update_lru_sizes (lruvec, lru, nr_zone_taken);return nr_taken; }
Signature · 7 lines
2.7.4 -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to [email protected]. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"[email protected]"> [email protected] </a>
Quoted 84 lines · Minchan Kim
Although there are a ton of free swap and anonymous LRU page in elgible zones, OOM happened.
balloon invoked oom-killer: gfp_mask=0x17080c0(GFP_KERNEL_ACCOUNT|__GFP_ZERO|__GFP_NOTRACK), nodemask=(null), order=0, oom_score_adj=0
CPU: 7 PID: 1138 Comm: balloon Not tainted 4.11.0-rc6-mm1-zram-00289-ge228d67e9677-dirty #17 Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS Ubuntu-1.8.2-1ubuntu1 04/01/2014 Call Trace: dump_stack+0x65/0x87 dump_header.isra.19+0x8f/0x20f ? preempt_count_add+0x9e/0xb0 ? _raw_spin_unlock_irqrestore+0x24/0x40 oom_kill_process+0x21d/0x3f0 ? has_capability_noaudit+0x17/0x20 out_of_memory+0xd8/0x390 __alloc_pages_slowpath+0xbc1/0xc50 ? anon_vma_interval_tree_insert+0x84/0x90 __alloc_pages_nodemask+0x1a5/0x1c0 pte_alloc_one+0x20/0x50 __pte_alloc+0x1e/0x110 __handle_mm_fault+0x919/0x960 handle_mm_fault+0x77/0x120 __do_page_fault+0x27a/0x550 trace_do_page_fault+0x43/0x150 do_async_page_fault+0x2c/0x90 async_page_fault+0x28/0x30 RIP: 0033:0x7fc4636bacb8 RSP: 002b:00007fff97c9c4c0 EFLAGS: 00010202 RAX: 00007fc3e818d000 RBX: 00007fc4639f8760 RCX: 00007fc46372e9ca RDX: 0000000000101002 RSI: 0000000000101000 RDI: 0000000000000000 RBP: 0000000000100010 R08: 00000000ffffffff R09: 0000000000000000 R10: 0000000000000022 R11: 00000000000a3901 R12: 00007fc3e818d010 R13: 0000000000101000 R14: 00007fc4639f87b8 R15: 00007fc4639f87b8Mem-Info:
active_anon:424716 inactive_anon:65314 isolated_anon:0
active_file:52 inactive_file:46 isolated_file:0
unevictable:0 dirty:27 writeback:0 unstable:0
slab_reclaimable:3967 slab_unreclaimable:4125
mapped:133 shmem:43 pagetables:1674 bounce:0
free:4637 free_pcp:225 free_cma:0
Node 0 active_anon:1698864kB inactive_anon:261256kB active_file:208kB inactive_file:184kB unevictable:0kB isolated(anon):0kB isolated(file):0kB mapped:532kB dirty:108kB writeback:0kB shmem:172kB writeback_tmp:0kB unstable:0kBall_unreclaimable? no
DMA free:7316kB min:32kB low:44kB high:56kB active_anon:8064kB inactive_anon:0kB active_file:0kB inactive_file:0kB unevictable:0kB writepending:0kB present:15992kB managed:15908kB mlocked:0kB slab_reclaimable:464kB slab_unreclaimable:40kB kernel_stack:0kB pagetables:24kB bounce:0kB free_pcp:0kB local_pcp:0kB free_cma:0kB lowmem_reserve[]: 0 992 992 1952
DMA32 free:9088kB min:2048kB low:3064kB high:4080kB active_anon:952176kB inactive_anon:0kB active_file:36kB inactive_file:0kB unevictable:0kB writepending:88kB present:1032192kB managed:1019388kB mlocked:0kB slab_reclaimable:13532kB slab_unreclaimable:16460kB kernel_stack:3552kB pagetables:6672kB bounce:0kB free_pcp:56kB local_pcp:24kB free_cma:0kB lowmem_reserve[]: 0 0 0 959
Movable free:3644kB min:1980kB low:2960kB high:3940kB active_anon:738560kB inactive_anon:261340kB active_file:188kB inactive_file:640kB unevictable:0kB writepending:20kB present:1048444kB managed:1010816kB mlocked:0kB slab_reclaimable:0kB slab_unreclaimable:0kB kernel_stack:0kB pagetables:0kB bounce:0kB free_pcp:832kB local_pcp:60kB free_cma:0kB lowmem_reserve[]: 0 0 0 0
DMA: 1*4kB (E) 0*8kB 18*16kB (E) 10*32kB (E) 10*64kB (E) 9*128kB (ME) 8*256kB (E) 2*512kB (E) 2*1024kB (E) 0*2048kB 0*4096kB = 7524kB
DMA32: 417*4kB (UMEH) 181*8kB (UMEH) 68*16kB (UMEH) 48*32kB (UMEH) 14*64kB (MH) 3*128kB (M) 1*256kB (H) 1*512kB (M) 2*1024kB (M) 0*2048kB 0*4096kB = 9836kB
Movable: 1*4kB (M) 1*8kB (M) 1*16kB (M) 1*32kB (M) 0*64kB 1*128kB (M) 2*256kB (M) 4*512kB (M) 1*1024kB (M) 0*2048kB 0*4096kB = 3772kB
378 total pagecache pages
17 pages in swap cache
Swap cache stats: add 17325, delete 17302, find 0/27
Free swap = 978940kB
Total swap = 1048572kB
524157 pages RAM
0 pages HighMem/MovableOnly
12629 pages reserved
0 pages cma reserved
0 pages hwpoisoned
[ pid ] uid tgidtotal_vmrssnr_ptesnr_pmdsswapentsoom_score_adjname[ 433] 0 433 4904 5 14 3 82 0 upstart-udev-br [ 438] 0 438 12371 5 27 3 191 -1000 systemd-udevdWith investigation, skipping page of
isolate_lru_pagesmakes reclaim void because it returns zeronr_takeneasily so LRU shrinking is effectively nothing and just increases priority aggressively. Finally, OOM happens.The problem is that
get_scan_countdeterminesnr_to_scanwith eligible zones so although priority drops to zero, it couldn't reclaim any pages if the LRU contains mostly ineligible pages.
get_scan_count:size = lruvec_lru_size(lruvec, lru, sc->reclaim_idx); size = size >> sc->priority;Assumes
sc->priorityis 0 and LRU list is as follows.N-N-N-N-H-H-H-H-H-H-H-H-H-H-H-H-H-H-H-H(Ie, small eligible pages are in the head of LRU but others are
almost ineligible pages)
Quoted 8 lines
In that case, size becomes 4 so VM want to scan 4 pages but 4 pages from tail of the LRU are not eligible pages.
Ifget_scan_countcounts skipped pages, it doesn't reclaim any pages remained after scanning 4 pages so it ends up OOM happening.This patch makes
isolate_lru_pagestry to scan pages until it encounters eligible zones's pages.
Quoted 1 line
Signed-off-by Minchan Kim <[email protected]>
Quoted 67 lines
---
* from v1
* put more words in description and code
* drop unncessarypages_skippedlist flushingmm/vmscan.c | 21 +++++++++++++++------ 1 file changed, 15 insertions(+), 6 deletions(-)mm/vmscan.c +15
-6@@ -1449,7 +1449,7 @@ static __always_inline void update_lru_sizes(struct lruvec *lruvec,* * Appropriate locks must be held before calling this function. * -* @nr_to_scan: The number of pages to look through on the list. +* @nr_to_scan: The number of eligible pages to look through on the list. * @lruvec: The LRU vector to pull pages from. * @dst: The temp list to put pages on to. * @nr_scanned: The number of pages that were scanned. @@ -1469,11 +1469,13 @@ static unsigned long isolate_lru_pages(unsigned long nr_to_scan,unsigned long nr_zone_taken[MAX_NR_ZONES ] = {0 };unsigned long nr_skipped[MAX_NR_ZONES ] = {0 , };unsigned long skipped =0 ; -unsigned long scan, nr_pages; +unsigned long scan, total_scan, nr_pages;LIST_HEAD (pages_skipped); -for (scan =0 ; scan < nr_to_scan && nr_taken < nr_to_scan && - !list_empty (src); scan++) { +for (total_scan = scan =0 ; scan < nr_to_scan && + nr_taken < nr_to_scan && + !list_empty (src); + total_scan++) {struct page *page; page =lru_to_page (src);@@ -1487,6 +1489,13 @@ static unsigned long isolate_lru_pages(unsigned long nr_to_scan,continue ; } +/* +* Do not count skipped pages because it makes the function to +* return with none isolated pages if the LRU mostly contains +* ineligible pages so that VM cannot reclaim any pages and +* trigger premature OOM. +*/ + scan++;switch (__isolate_lru_page (page, mode)) {case 0 : nr_pages =hpage_nr_pages (page);@@ -1524,9 +1533,9 @@ static unsigned long isolate_lru_pages(unsigned long nr_to_scan, skipped += nr_skipped[zid]; } } - *nr_scanned = scan; + *nr_scanned = total_scan;trace_mm_vmscan_lru_isolate (sc->reclaim_idx, sc->order, nr_to_scan, - scan, skipped, nr_taken, mode, lru); + total_scan, skipped, nr_taken, mode, lru);update_lru_sizes (lruvec, lru, nr_zone_taken);return nr_taken; }Signature · 1 line
2.7.4
Signature · 8 lines
Michal Hocko SUSE Labs -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to [email protected]. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"[email protected]"> [email protected] </a>
Quoted 89 lines · Minchan Kim
Although there are a ton of free swap and anonymous LRU page in elgible zones, OOM happened.
balloon invoked oom-killer: gfp_mask=0x17080c0(GFP_KERNEL_ACCOUNT|__GFP_ZERO|__GFP_NOTRACK), nodemask=(null), order=0, oom_score_adj=0
CPU: 7 PID: 1138 Comm: balloon Not tainted 4.11.0-rc6-mm1-zram-00289-ge228d67e9677-dirty #17 Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS Ubuntu-1.8.2-1ubuntu1 04/01/2014 Call Trace: dump_stack+0x65/0x87 dump_header.isra.19+0x8f/0x20f ? preempt_count_add+0x9e/0xb0 ? _raw_spin_unlock_irqrestore+0x24/0x40 oom_kill_process+0x21d/0x3f0 ? has_capability_noaudit+0x17/0x20 out_of_memory+0xd8/0x390 __alloc_pages_slowpath+0xbc1/0xc50 ? anon_vma_interval_tree_insert+0x84/0x90 __alloc_pages_nodemask+0x1a5/0x1c0 pte_alloc_one+0x20/0x50 __pte_alloc+0x1e/0x110 __handle_mm_fault+0x919/0x960 handle_mm_fault+0x77/0x120 __do_page_fault+0x27a/0x550 trace_do_page_fault+0x43/0x150 do_async_page_fault+0x2c/0x90 async_page_fault+0x28/0x30 RIP: 0033:0x7fc4636bacb8 RSP: 002b:00007fff97c9c4c0 EFLAGS: 00010202 RAX: 00007fc3e818d000 RBX: 00007fc4639f8760 RCX: 00007fc46372e9ca RDX: 0000000000101002 RSI: 0000000000101000 RDI: 0000000000000000 RBP: 0000000000100010 R08: 00000000ffffffff R09: 0000000000000000 R10: 0000000000000022 R11: 00000000000a3901 R12: 00007fc3e818d010 R13: 0000000000101000 R14: 00007fc4639f87b8 R15: 00007fc4639f87b8Mem-Info:
active_anon:424716 inactive_anon:65314 isolated_anon:0
active_file:52 inactive_file:46 isolated_file:0
unevictable:0 dirty:27 writeback:0 unstable:0
slab_reclaimable:3967 slab_unreclaimable:4125
mapped:133 shmem:43 pagetables:1674 bounce:0
free:4637 free_pcp:225 free_cma:0
Node 0 active_anon:1698864kB inactive_anon:261256kB active_file:208kB inactive_file:184kB unevictable:0kB isolated(anon):0kB isolated(file):0kB mapped:532kB dirty:108kB writeback:0kB shmem:172kB writeback_tmp:0kB unstable:0kBall_unreclaimable? no
DMA free:7316kB min:32kB low:44kB high:56kB active_anon:8064kB inactive_anon:0kB active_file:0kB inactive_file:0kB unevictable:0kB writepending:0kB present:15992kB managed:15908kB mlocked:0kB slab_reclaimable:464kB slab_unreclaimable:40kB kernel_stack:0kB pagetables:24kB bounce:0kB free_pcp:0kB local_pcp:0kB free_cma:0kB lowmem_reserve[]: 0 992 992 1952
DMA32 free:9088kB min:2048kB low:3064kB high:4080kB active_anon:952176kB inactive_anon:0kB active_file:36kB inactive_file:0kB unevictable:0kB writepending:88kB present:1032192kB managed:1019388kB mlocked:0kB slab_reclaimable:13532kB slab_unreclaimable:16460kB kernel_stack:3552kB pagetables:6672kB bounce:0kB free_pcp:56kB local_pcp:24kB free_cma:0kB lowmem_reserve[]: 0 0 0 959
Movable free:3644kB min:1980kB low:2960kB high:3940kB active_anon:738560kB inactive_anon:261340kB active_file:188kB inactive_file:640kB unevictable:0kB writepending:20kB present:1048444kB managed:1010816kB mlocked:0kB slab_reclaimable:0kB slab_unreclaimable:0kB kernel_stack:0kB pagetables:0kB bounce:0kB free_pcp:832kB local_pcp:60kB free_cma:0kB lowmem_reserve[]: 0 0 0 0
DMA: 1*4kB (E) 0*8kB 18*16kB (E) 10*32kB (E) 10*64kB (E) 9*128kB (ME) 8*256kB (E) 2*512kB (E) 2*1024kB (E) 0*2048kB 0*4096kB = 7524kB
DMA32: 417*4kB (UMEH) 181*8kB (UMEH) 68*16kB (UMEH) 48*32kB (UMEH) 14*64kB (MH) 3*128kB (M) 1*256kB (H) 1*512kB (M) 2*1024kB (M) 0*2048kB 0*4096kB = 9836kB
Movable: 1*4kB (M) 1*8kB (M) 1*16kB (M) 1*32kB (M) 0*64kB 1*128kB (M) 2*256kB (M) 4*512kB (M) 1*1024kB (M) 0*2048kB 0*4096kB = 3772kB
378 total pagecache pages
17 pages in swap cache
Swap cache stats: add 17325, delete 17302, find 0/27
Free swap = 978940kB
Total swap = 1048572kB
524157 pages RAM
0 pages HighMem/MovableOnly
12629 pages reserved
0 pages cma reserved
0 pages hwpoisoned
[ pid ] uid tgidtotal_vmrssnr_ptesnr_pmdsswapentsoom_score_adjname[ 433] 0 433 4904 5 14 3 82 0 upstart-udev-br [ 438] 0 438 12371 5 27 3 191 -1000 systemd-udevdWith investigation, skipping page of
isolate_lru_pagesmakes reclaim void because it returns zeronr_takeneasily so LRU shrinking is effectively nothing and just increases priority aggressively. Finally, OOM happens.The problem is that
get_scan_countdeterminesnr_to_scanwith eligible zones so although priority drops to zero, it couldn't reclaim any pages if the LRU contains mostly ineligible pages.
get_scan_count:size = lruvec_lru_size(lruvec, lru, sc->reclaim_idx); size = size >> sc->priority;Assumes
sc->priorityis 0 and LRU list is as follows.N-N-N-N-H-H-H-H-H-H-H-H-H-H-H-H-H-H-H-H(Ie, small eligible pages are in the head of LRU but others are
almost ineligible pages)In that case, size becomes 4 so VM want to scan 4 pages but 4 pages from tail of the LRU are not eligible pages.
Ifget_scan_countcounts skipped pages, it doesn't reclaim any pages remained after scanning 4 pages so it ends up OOM happening.
Quoted 4 lines
This patch makes
isolate_lru_pagestry to scan pages until it encounters eligible zones's pages.Signed-off-by Minchan Kim <[email protected]>