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Subject[PATCH] zram_drv: add __GFP_NOMEMALLOC not to use ALLOC_NO_WATERMARKS
Date
The atomic page allocation failure sometimes happened, and most of them
seem to occur during boot time.

<4>[ 59.707645] system_server: page allocation failure: order:0, mode:0xa20(GFP_ATOMIC), nodemask=(null),cpuset=foreground-boost,mems_allowed=0
<4>[ 59.707676] CPU: 5 PID: 1209 Comm: system_server Tainted: G S O 5.4.161-qgki-24219806-abA236USQU0AVE1 #1
<4>[ 59.707691] Call trace:
<4>[ 59.707702] dump_backtrace.cfi_jt+0x0/0x4
<4>[ 59.707712] show_stack+0x18/0x24
<4>[ 59.707719] dump_stack+0xa4/0xe0
<4>[ 59.707728] warn_alloc+0x114/0x194
<4>[ 59.707734] __alloc_pages_slowpath+0x828/0x83c
<4>[ 59.707740] __alloc_pages_nodemask+0x2b4/0x310
<4>[ 59.707747] alloc_slab_page+0x40/0x5c8
<4>[ 59.707753] new_slab+0x404/0x420
<4>[ 59.707759] ___slab_alloc+0x224/0x3b0
<4>[ 59.707765] __kmalloc+0x37c/0x394
<4>[ 59.707773] context_struct_to_string+0x110/0x1b8
<4>[ 59.707778] context_add_hash+0x6c/0xc8
<4>[ 59.707785] security_compute_sid.llvm.13699573597798246927+0x508/0x5d8
<4>[ 59.707792] security_transition_sid+0x2c/0x38
<4>[ 59.707804] selinux_socket_create+0xa0/0xd8
<4>[ 59.707811] security_socket_create+0x68/0xbc
<4>[ 59.707818] __sock_create+0x8c/0x2f8
<4>[ 59.707823] __sys_socket+0x94/0x19c
<4>[ 59.707829] __arm64_sys_socket+0x20/0x30
<4>[ 59.707836] el0_svc_common+0x100/0x1e0
<4>[ 59.707841] el0_svc_handler+0x68/0x74
<4>[ 59.707848] el0_svc+0x8/0xc
<4>[ 59.707853] Mem-Info:
<4>[ 59.707890] active_anon:223569 inactive_anon:74412 isolated_anon:0
<4>[ 59.707890] active_file:51395 inactive_file:176622 isolated_file:0
<4>[ 59.707890] unevictable:1018 dirty:211 writeback:4 unstable:0
<4>[ 59.707890] slab_reclaimable:14398 slab_unreclaimable:61909
<4>[ 59.707890] mapped:134779 shmem:1231 pagetables:26706 bounce:0
<4>[ 59.707890] free:528 free_pcp:844 free_cma:147
<4>[ 59.707900] Node 0 active_anon:894276kB inactive_anon:297648kB active_file:205580kB inactive_file:706488kB unevictable:4072kB isolated(anon):0kB isolated(file):0kB mapped:539116kB dirty:844kB writeback:16kB shmem:4924kB writeback_tmp:0kB unstable:0kB all_unreclaimable? no
<4>[ 59.707912] Normal free:2112kB min:7244kB low:68892kB high:72180kB active_anon:893140kB inactive_anon:297660kB active_file:204740kB inactive_file:706396kB unevictable:4072kB writepending:860kB present:3626812kB managed:3288700kB mlocked:4068kB kernel_stack:62416kB shadow_call_stack:15656kB pagetables:106824kB bounce:0kB free_pcp:3372kB local_pcp:176kB free_cma:588kB
<4>[ 59.707915] lowmem_reserve[]: 0 0
<4>[ 59.707922] Normal: 8*4kB (H) 5*8kB (H) 13*16kB (H) 25*32kB (H) 0*64kB 0*128kB 0*256kB 0*512kB 0*1024kB 0*2048kB 0*4096kB = 1080kB
<4>[ 59.707942] 242549 total pagecache pages
<4>[ 59.707951] 12446 pages in swap cache
<4>[ 59.707956] Swap cache stats: add 212408, delete 199969, find 36869/71571
<4>[ 59.707961] Free swap = 3445756kB
<4>[ 59.707965] Total swap = 4194300kB
<4>[ 59.707969] 906703 pages RAM
<4>[ 59.707973] 0 pages HighMem/MovableOnly
<4>[ 59.707978] 84528 pages reserved
<4>[ 59.707982] 49152 pages cma reserved

The kswapd or other reclaim contexts may not prepare enough free pages
for too many atomic allocations occurred in short time. But zram may not
be helpful for this atomic allocation even though zram is used to
reclaim.

To get one zs object for a specific size, zram may allocate serveral
pages. And this can be happened on different class sizes at the same
time. It means zram may consume more pages to reclaim only one page.
This inefficiency may consume all free pages below watmerk min by a
process having PF_MEMALLOC like kswapd.

We can avoid this by adding __GFP_NOMEMALLOC. PF_MEMALLOC process won't
use ALLOC_NO_WATERMARKS.

Signed-off-by: Jaewon Kim <jaewon31.kim@samsung.com>
---
drivers/block/zram/zram_drv.c | 1 +
1 file changed, 1 insertion(+)

diff --git a/drivers/block/zram/zram_drv.c b/drivers/block/zram/zram_drv.c
index b8549c61ff2c..39cd1397ed3b 100644
--- a/drivers/block/zram/zram_drv.c
+++ b/drivers/block/zram/zram_drv.c
@@ -1383,6 +1383,7 @@ static int __zram_bvec_write(struct zram *zram, struct bio_vec *bvec,

handle = zs_malloc(zram->mem_pool, comp_len,
__GFP_KSWAPD_RECLAIM |
+ __GFP_NOMEMALLOC |
__GFP_NOWARN |
__GFP_HIGHMEM |
__GFP_MOVABLE);
--
2.17.1
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