Hi Jaewon, On Tue, Jun 09, 2020 at 06:51:28PM +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. > > 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 > > This is an example of ALLOC_HARDER allocation failure. > > <4>[ 6207.637280] [3: Binder:9343_3:22875] Binder:9343_3: page allocation > failure: order:0, mode:0x480020(GFP_ATOMIC), nodemask=(null) > <4>[ 6207.637311] [3: Binder:9343_3:22875] Call trace: > <4>[ 6207.637346] [3: Binder:9343_3:22875] [<ffffff8008f40f8c>] > dump_stack+0xb8/0xf0 > <4>[ 6207.637356] [3: Binder:9343_3:22875] [<ffffff8008223320>] > warn_alloc+0xd8/0x12c > <4>[ 6207.637365] [3: Binder:9343_3:22875] [<ffffff80082245e4>] > __alloc_pages_nodemask+0x120c/0x1250 > <4>[ 6207.637374] [3: Binder:9343_3:22875] [<ffffff800827f6e8>] > new_slab+0x128/0x604 > <4>[ 6207.637381] [3: Binder:9343_3:22875] [<ffffff800827b0cc>] > ___slab_alloc+0x508/0x670 > <4>[ 6207.637387] [3: Binder:9343_3:22875] [<ffffff800827ba00>] > __kmalloc+0x2f8/0x310 > <4>[ 6207.637396] [3: Binder:9343_3:22875] [<ffffff80084ac3e0>] > context_struct_to_string+0x104/0x1cc > <4>[ 6207.637404] [3: Binder:9343_3:22875] [<ffffff80084ad8fc>] > security_sid_to_context_core+0x74/0x144 > <4>[ 6207.637412] [3: Binder:9343_3:22875] [<ffffff80084ad880>] > security_sid_to_context+0x10/0x18 > <4>[ 6207.637421] [3: Binder:9343_3:22875] [<ffffff800849bd80>] > selinux_secid_to_secctx+0x20/0x28 > <4>[ 6207.637430] [3: Binder:9343_3:22875] [<ffffff800849109c>] > security_secid_to_secctx+0x3c/0x70 > <4>[ 6207.637442] [3: Binder:9343_3:22875] [<ffffff8008bfe118>] > binder_transaction+0xe68/0x454c > <4>[ 6207.637569] [3: Binder:9343_3:22875] Mem-Info: > <4>[ 6207.637595] [3: Binder:9343_3:22875] active_anon:102061 > inactive_anon:81551 isolated_anon:0 > <4>[ 6207.637595] [3: Binder:9343_3:22875] active_file:59102 > inactive_file:68924 isolated_file:64 > <4>[ 6207.637595] [3: Binder:9343_3:22875] unevictable:611 dirty:63 > writeback:0 unstable:0 > <4>[ 6207.637595] [3: Binder:9343_3:22875] slab_reclaimable:13324 > slab_unreclaimable:44354 > <4>[ 6207.637595] [3: Binder:9343_3:22875] mapped:83015 shmem:4858 > pagetables:26316 bounce:0 > <4>[ 6207.637595] [3: Binder:9343_3:22875] free:2727 free_pcp:1035 > free_cma:178 > <4>[ 6207.637616] [3: Binder:9343_3:22875] 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 > <4>[ 6207.637627] [3: Binder:9343_3:22875] 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 > <4>[ 6207.637632] [3: Binder:9343_3:22875] lowmem_reserve[]: 0 0 > <4>[ 6207.637637] [3: Binder:9343_3:22875] 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 > <4>[ 6207.637655] [3: Binder:9343_3:22875] 138826 total pagecache pages > <4>[ 6207.637663] [3: Binder:9343_3:22875] 5460 pages in swap cache > <4>[ 6207.637668] [3: Binder:9343_3:22875] Swap cache stats: add 8273090, > delete 8267506, find 1004381/4060142 > > This is an example of ALLOC_NO_WATERMARKS allocation failure. > > <6>[ 156.701551] [4: kswapd0: 1209] kswapd0 cpuset=/ mems_allowed=0 > <4>[ 156.701563] [4: kswapd0: 1209] CPU: 4 PID: 1209 Comm: kswapd0 > Tainted: G W 4.14.113-18113966 #1 > <4>[ 156.701572] [4: kswapd0: 1209] Call trace: > <4>[ 156.701605] [4: kswapd0: 1209] [<0000000000000000>] > dump_stack+0x68/0x90 > <4>[ 156.701612] [4: kswapd0: 1209] [<0000000000000000>] > warn_alloc+0x104/0x198 > <4>[ 156.701617] [4: kswapd0: 1209] [<0000000000000000>] > __alloc_pages_nodemask+0xdc0/0xdf0 > <4>[ 156.701623] [4: kswapd0: 1209] [<0000000000000000>] > zs_malloc+0x148/0x3d0 > <4>[ 156.701630] [4: kswapd0: 1209] [<0000000000000000>] > zram_bvec_rw+0x250/0x568 > <4>[ 156.701634] [4: kswapd0: 1209] [<0000000000000000>] > zram_rw_page+0x8c/0xe0 > <4>[ 156.701640] [4: kswapd0: 1209] [<0000000000000000>] > bdev_write_page+0x70/0xbc > <4>[ 156.701645] [4: kswapd0: 1209] [<0000000000000000>] > __swap_writepage+0x58/0x37c > <4>[ 156.701649] [4: kswapd0: 1209] [<0000000000000000>] > swap_writepage+0x40/0x4c > <4>[ 156.701654] [4: kswapd0: 1209] [<0000000000000000>] > shrink_page_list+0xc3c/0xf54 > <4>[ 156.701659] [4: kswapd0: 1209] [<0000000000000000>] > shrink_inactive_list+0x2b0/0x61c > <4>[ 156.701664] [4: kswapd0: 1209] [<0000000000000000>] > shrink_node_memcg+0x23c/0x618 > <4>[ 156.701668] [4: kswapd0: 1209] [<0000000000000000>] > shrink_node+0x1c8/0x304 > <4>[ 156.701673] [4: kswapd0: 1209] [<0000000000000000>] > kswapd+0x680/0x7c4 > <4>[ 156.701679] [4: kswapd0: 1209] [<0000000000000000>] > kthread+0x110/0x120 > <4>[ 156.701684] [4: kswapd0: 1209] [<0000000000000000>] > ret_from_fork+0x10/0x18 > <4>[ 156.701689] [4: kswapd0: 1209] Mem-Info: > <4>[ 156.701712] [4: kswapd0: 1209] active_anon:88690 > inactive_anon:88630 isolated_anon:0 > <4>[ 156.701712] [4: kswapd0: 1209] active_file:99173 > inactive_file:169305 isolated_file:32 > <4>[ 156.701712] [4: kswapd0: 1209] unevictable:48292 dirty:538 > writeback:38 unstable:0 > <4>[ 156.701712] [4: kswapd0: 1209] slab_reclaimable:15131 > slab_unreclaimable:47762 > <4>[ 156.701712] [4: kswapd0: 1209] mapped:274654 shmem:2824 > pagetables:25088 bounce:0 > <4>[ 156.701712] [4: kswapd0: 1209] free:2489 free_pcp:444 > free_cma:3 > <4>[ 156.701728] [4: kswapd0: 1209] Node 0 active_anon:354760kB > inactive_anon:354520kB active_file:396692kB inactive_file:677220kB > unevictable:193168kB isolated(anon):0kB isolated(file):128kB mapped:1098616kB > dirty:2152kB writeback:152kB shmem:11296kB writeback_tmp:0kB unstable:0kB > all_unreclaimable? no > <4>[ 156.701738] [4: kswapd0: 1209] Normal free:9956kB min:7428kB > low:93440kB high:97032kB active_anon:355176kB inactive_anon:354580kB > active_file:396196kB inactive_file:677284kB unevictable:193168kB > writepending:2304kB present:4081664kB managed:3593324kB mlocked:193168kB > kernel_stack:55008kB pagetables:100352kB bounce:0kB free_pcp:1776kB > local_pcp:656kB free_cma:12kB > <4>[ 156.701741] [4: kswapd0: 1209] lowmem_reserve[]: 0 0 > <4>[ 156.701747] [4: kswapd0: 1209] Normal: 196*4kB (H) 141*8kB (H) > 109*16kB (H) 63*32kB (H) 20*64kB (H) 8*128kB (H) 2*256kB (H) 1*512kB (H) > 0*1024kB 0*2048kB 0*4096kB = 9000kB > > Signed-off-by: Jaewon Kim <jaewon31....@samsung.com> > Reported-by: Yong-Taek Lee <ytk....@samsung.com> > --- > mm/page_alloc.c | 13 +++++++++++-- > 1 file changed, 11 insertions(+), 2 deletions(-) > > diff --git a/mm/page_alloc.c b/mm/page_alloc.c > index 13cc653122b7..00869378d387 100644 > --- a/mm/page_alloc.c > +++ b/mm/page_alloc.c > @@ -3553,6 +3553,11 @@ static inline bool zone_watermark_fast(struct zone *z, > unsigned int order, > { > long free_pages = zone_page_state(z, NR_FREE_PAGES); > long cma_pages = 0; > + long highatomic = 0; > + const bool alloc_harder = (alloc_flags & (ALLOC_HARDER|ALLOC_OOM)); > + > + if (likely(!alloc_harder)) > + highatomic = z->nr_reserved_highatomic; > > #ifdef CONFIG_CMA > /* If allocation can't use CMA areas don't use free CMA pages */ > @@ -3567,8 +3572,12 @@ static inline bool zone_watermark_fast(struct zone *z, > unsigned int order, > * the caller is !atomic then it'll uselessly search the free > * list. That corner case is then slower but it is harmless. > */ > - if (!order && (free_pages - cma_pages) > mark + > z->lowmem_reserve[classzone_idx]) > - return true; > + if (!order) { > + long fast_free = free_pages - cma_pages - highatomic;
With your change, it seems we share most code for getting free_pages between zone_watermark_fast and __zone_watermark_ok. Only difference between them is min calculation. If so, can we share most code between them via introducing like __zone_watermark_free static inline function? So, we didn't miss one place in future if we change something. > + > + if (fast_free > mark + z->lowmem_reserve[classzone_idx]) > + return true; > + } > > return __zone_watermark_ok(z, order, mark, classzone_idx, alloc_flags, > free_pages); > -- > 2.17.1 >