On Sat, Jun 20, 2020 at 08:59:58AM +0900, Jaewon Kim wrote:
> zone_watermark_fast was introduced by commit 48ee5f3696f6 ("mm,
> page_alloc: shortcut watermark checks for order-0 pages"). The commit
> simply checks if free pages is bigger than watermark without additional
> calculation such like reducing watermark.
>
> It considered free cma pages but it did not consider highatomic
> reserved. This may incur exhaustion of free pages except high order
> atomic free pages.
>
> Assume that reserved_highatomic pageblock is bigger than watermark min,
> and there are only few free pages except high order atomic free. Because
> zone_watermark_fast passes the allocation without considering high order
> atomic free, normal reclaimable allocation like GFP_HIGHUSER will
> consume all the free pages. Then finally order-0 atomic allocation may
> fail on allocation.
>
> This means watermark min is not protected against non-atomic allocation.
> The order-0 atomic allocation with ALLOC_HARDER unwantedly can be
> failed. Additionally the __GFP_MEMALLOC allocation with
> ALLOC_NO_WATERMARKS also can be failed.
>
> To avoid the problem, zone_watermark_fast should consider highatomic
> reserve. If the actual size of high atomic free is counted accurately
> like cma free, we may use it. On this patch just use
> nr_reserved_highatomic. Additionally introduce
> __zone_watermark_unusable_free to factor out common parts between
> zone_watermark_fast and __zone_watermark_ok.
>
> This is an example of ALLOC_HARDER allocation failure using v4.19 based
> kernel.
>
> Binder:9343_3: page allocation failure: order:0, mode:0x480020(GFP_ATOMIC), nodemask=(null)
> Call trace:
> [<ffffff8008f40f8c>] dump_stack+0xb8/0xf0
> [<ffffff8008223320>] warn_alloc+0xd8/0x12c
> [<ffffff80082245e4>] __alloc_pages_nodemask+0x120c/0x1250
> [<ffffff800827f6e8>] new_slab+0x128/0x604
> [<ffffff800827b0cc>] ___slab_alloc+0x508/0x670
> [<ffffff800827ba00>] __kmalloc+0x2f8/0x310
> [<ffffff80084ac3e0>] context_struct_to_string+0x104/0x1cc
> [<ffffff80084ad8fc>] security_sid_to_context_core+0x74/0x144
> [<ffffff80084ad880>] security_sid_to_context+0x10/0x18
> [<ffffff800849bd80>] selinux_secid_to_secctx+0x20/0x28
> [<ffffff800849109c>] security_secid_to_secctx+0x3c/0x70
> [<ffffff8008bfe118>] binder_transaction+0xe68/0x454c
> Mem-Info:
> active_anon:102061 inactive_anon:81551 isolated_anon:0
> active_file:59102 inactive_file:68924 isolated_file:64
> unevictable:611 dirty:63 writeback:0 unstable:0
> slab_reclaimable:13324 slab_unreclaimable:44354
> mapped:83015 shmem:4858 pagetables:26316 bounce:0
> free:2727 free_pcp:1035 free_cma:178
> Node 0 active_anon:408244kB inactive_anon:326204kB active_file:236408kB inactive_file:275696kB unevictable:2444kB isolated(anon):0kB isolated(file):256kB mapped:332060kB dirty:252kB writeback:0kB shmem:19432kB writeback_tmp:0kB unstable:0kB all_unreclaimable? no
> Normal free:10908kB min:6192kB low:44388kB high:47060kB active_anon:409160kB inactive_anon:325924kB active_file:235820kB inactive_file:276628kB unevictable:2444kB writepending:252kB present:3076096kB managed:2673676kB mlocked:2444kB kernel_stack:62512kB pagetables:105264kB bounce:0kB free_pcp:4140kB local_pcp:40kB free_cma:712kB
> lowmem_reserve[]: 0 0
> Normal: 505*4kB (H) 357*8kB (H) 201*16kB (H) 65*32kB (H) 1*64kB (H) 0*128kB 0*256kB 0*512kB 0*1024kB 0*2048kB 0*4096kB = 10236kB
> 138826 total pagecache pages
> 5460 pages in swap cache
> Swap cache stats: add 8273090, delete 8267506, find 1004381/4060142
>
> This is an example of ALLOC_NO_WATERMARKS allocation failure using v4.14
> based kernel.
>
> kswapd0: page allocation failure: order:0, mode:0x140000a(GFP_NOIO|__GFP_HIGHMEM|__GFP_MOVABLE), nodemask=(null)
> kswapd0 cpuset=/ mems_allowed=0
> CPU: 4 PID: 1221 Comm: kswapd0 Not tainted 4.14.113-18770262-userdebug #1
> Call trace:
> [<0000000000000000>] dump_backtrace+0x0/0x248
> [<0000000000000000>] show_stack+0x18/0x20
> [<0000000000000000>] __dump_stack+0x20/0x28
> [<0000000000000000>] dump_stack+0x68/0x90
> [<0000000000000000>] warn_alloc+0x104/0x198
> [<0000000000000000>] __alloc_pages_nodemask+0xdc0/0xdf0
> [<0000000000000000>] zs_malloc+0x148/0x3d0
> [<0000000000000000>] zram_bvec_rw+0x410/0x798
> [<0000000000000000>] zram_rw_page+0x88/0xdc
> [<0000000000000000>] bdev_write_page+0x70/0xbc
> [<0000000000000000>] __swap_writepage+0x58/0x37c
> [<0000000000000000>] swap_writepage+0x40/0x4c
> [<0000000000000000>] shrink_page_list+0xc30/0xf48
> [<0000000000000000>] shrink_inactive_list+0x2b0/0x61c
> [<0000000000000000>] shrink_node_memcg+0x23c/0x618
> [<0000000000000000>] shrink_node+0x1c8/0x304
> [<0000000000000000>] kswapd+0x680/0x7c4
> [<0000000000000000>] kthread+0x110/0x120
> [<0000000000000000>] ret_from_fork+0x10/0x18
> Mem-Info:
> active_anon:111826 inactive_anon:65557 isolated_anon:0\x0a active_file:44260 inactive_file:83422 isolated_file:0\x0a unevictable:4158 dirty:117 writeback:0 unstable:0\x0a slab_reclaimable:13943 slab_unreclaimable:43315\x0a mapped:102511 shmem:3299 pagetables:19566 bounce:0\x0a free:3510 free_pcp:553 free_cma:0
> Node 0 active_anon:447304kB inactive_anon:262228kB active_file:177040kB inactive_file:333688kB unevictable:16632kB isolated(anon):0kB isolated(file):0kB mapped:410044kB d irty:468kB writeback:0kB shmem:13196kB writeback_tmp:0kB unstable:0kB all_unreclaimable? no
> Normal free:14040kB min:7440kB low:94500kB high:98136kB reserved_highatomic:32768KB active_anon:447336kB inactive_anon:261668kB active_file:177572kB inactive_file:333768k B unevictable:16632kB writepending:480kB present:4081664kB managed:3637088kB mlocked:16632kB kernel_stack:47072kB pagetables:78264kB bounce:0kB free_pcp:2280kB local_pcp:720kB free_cma:0kB [ 4738.329607] lowmem_reserve[]: 0 0
> Normal: 860*4kB (H) 453*8kB (H) 180*16kB (H) 26*32kB (H) 34*64kB (H) 6*128kB (H) 2*256kB (H) 0*512kB 0*1024kB 0*2048kB 0*4096kB = 14232kB
>
> This is trace log which shows GFP_HIGHUSER consumes free pages right
> before ALLOC_NO_WATERMARKS.
>
> <...>-22275 [006] .... 889.213383: mm_page_alloc: page=00000000d2be5665 pfn=970744 order=0 migratetype=0 nr_free=3650 gfp_flags=GFP_HIGHUSER|__GFP_ZERO
> <...>-22275 [006] .... 889.213385: mm_page_alloc: page=000000004b2335c2 pfn=970745 order=0 migratetype=0 nr_free=3650 gfp_flags=GFP_HIGHUSER|__GFP_ZERO
> <...>-22275 [006] .... 889.213387: mm_page_alloc: page=00000000017272e1 pfn=970278 order=0 migratetype=0 nr_free=3650 gfp_flags=GFP_HIGHUSER|__GFP_ZERO
> <...>-22275 [006] .... 889.213389: mm_page_alloc: page=00000000c4be79fb pfn=970279 order=0 migratetype=0 nr_free=3650 gfp_flags=GFP_HIGHUSER|__GFP_ZERO
> <...>-22275 [006] .... 889.213391: mm_page_alloc: page=00000000f8a51d4f pfn=970260 order=0 migratetype=0 nr_free=3650 gfp_flags=GFP_HIGHUSER|__GFP_ZERO
> <...>-22275 [006] .... 889.213393: mm_page_alloc: page=000000006ba8f5ac pfn=970261 order=0 migratetype=0 nr_free=3650 gfp_flags=GFP_HIGHUSER|__GFP_ZERO
> <...>-22275 [006] .... 889.213395: mm_page_alloc: page=00000000819f1cd3 pfn=970196 order=0 migratetype=0 nr_free=3650 gfp_flags=GFP_HIGHUSER|__GFP_ZERO
> <...>-22275 [006] .... 889.213396: mm_page_alloc: page=00000000f6b72a64 pfn=970197 order=0 migratetype=0 nr_free=3650 gfp_flags=GFP_HIGHUSER|__GFP_ZERO
> kswapd0-1207 [005] ...1 889.213398: mm_page_alloc: page= (null) pfn=0 order=0 migratetype=1 nr_free=3650 gfp_flags=GFP_NOWAIT|__GFP_HIGHMEM|__GFP_NOWARN|__GFP_MOVABLE
>
> Reported-by: Yong-Taek Lee <ytk.lee@xxxxxxxxxxx>
> Suggested-by: Minchan Kim <minchan@xxxxxxxxxx>
> Signed-off-by: Jaewon Kim <jaewon31.kim@xxxxxxxxxxx>
> Acked-by: Vlastimil Babka <vbabka@xxxxxxx>
Acked-by: Mel Gorman <mgorman@xxxxxxxxxxxxxxxxxxx>
--
Mel Gorman
SUSE Labs
