システムログの「一般」メモリ領域が最小制限未満に下がると、Out of Memory Killerはプロセスを終了しますが、「HighMem」領域にはまだ利用可能なメモリが多いことを読みました。なぜこれが起こっているのか、それを防ぐために私ができることがあるのか混乱しています。あるリージョンに使用可能なメモリがない場合、プロセスが特定のリージョンのメモリを必要としない限り、カーネルは別のリージョンのメモリを割り当てると仮定しました。ただし、この場合、OOMを引き起こすアプリケーションはPythonなので、次のことができます。 Normal Area Memoryが必要な理由を具体的に考えないでください。
最近の典型的な例は次のとおりです。
Feb 2 04:10:01 ldr kernel: python invoked oom-killer: gfp_mask=0x2084d0, order=0, oom_score_adj=0
Feb 2 04:10:01 ldr kernel: python cpuset=/ mems_allowed=0
Feb 2 04:10:01 ldr kernel: CPU: 0 PID: 593 Comm: python Tainted: G O 3.14.24-wt-ldr-TC #4
Feb 2 04:10:01 ldr kernel: Hardware name: Eurotech, Inc. Catalyst TC/Catalyst TC, BIOS 04.08.05.01 02/03/2017
Feb 2 04:10:01 ldr kernel: 00000000 00000000 f336fd7c c171e79e f4f03580 f336fdd8 c171b7a0 c1908d18
Feb 2 04:10:01 ldr kernel: f4f03954 002084d0 00000000 00000000 f336fdb8 c1106774 00000000 00000000
Feb 2 04:10:01 ldr kernel: f336fdb4 002084d0 00000000 f336fdd8 c13ac8d2 c1109634 f336fde8 f4f042e0
Feb 2 04:10:01 ldr kernel: Call Trace:
Feb 2 04:10:01 ldr kernel: [<c171e79e>] dump_stack+0x4b/0x75
Feb 2 04:10:01 ldr kernel: [<c171b7a0>] dump_header.isra.9+0x77/0x1ee
Feb 2 04:10:01 ldr kernel: [<c1106774>] ? shrink_slab+0xb4/0xf0
Feb 2 04:10:01 ldr kernel: [<c13ac8d2>] ? ___ratelimit+0x82/0x100
Feb 2 04:10:01 ldr kernel: [<c1109634>] ? do_try_to_free_pages+0x404/0x420
Feb 2 04:10:01 ldr kernel: [<c10f9fac>] oom_kill_process+0x1dc/0x360
Feb 2 04:10:01 ldr kernel: [<c10486d6>] ? has_ns_capability_noaudit+0x36/0x50
Feb 2 04:10:01 ldr kernel: [<c1048704>] ? has_capability_noaudit+0x14/0x20
Feb 2 04:10:01 ldr kernel: [<c10f9c87>] ? oom_badness+0xa7/0x100
Feb 2 04:10:01 ldr kernel: [<c10f9d29>] ? oom_scan_process_thread+0x49/0xc0
Feb 2 04:10:01 ldr kernel: [<c10fa4d4>] out_of_memory+0x1f4/0x2d0
Feb 2 04:10:01 ldr kernel: [<c10fe557>] __alloc_pages_nodemask+0x937/0x950
Feb 2 04:10:01 ldr kernel: [<c10fe58d>] __get_free_pages+0x1d/0x30
Feb 2 04:10:01 ldr kernel: [<c103b3be>] pgd_alloc+0x1e/0x130
Feb 2 04:10:01 ldr kernel: [<c103dfc0>] mm_init+0xc0/0xf0
Feb 2 04:10:01 ldr kernel: [<c103e256>] mm_alloc+0x56/0xa0
Feb 2 04:10:01 ldr kernel: [<c1143ddf>] do_execve+0x19f/0x5a0
Feb 2 04:10:01 ldr kernel: [<c1144389>] SyS_execve+0x29/0x40
Feb 2 04:10:01 ldr kernel: [<c172a6be>] sysenter_do_call+0x12/0x12
Feb 2 04:10:01 ldr kernel: Mem-Info:
Feb 2 04:10:01 ldr kernel: DMA per-cpu:
Feb 2 04:10:01 ldr kernel: CPU 0: hi: 0, btch: 1 usd: 0
Feb 2 04:10:01 ldr kernel: CPU 1: hi: 0, btch: 1 usd: 0
Feb 2 04:10:01 ldr kernel: Normal per-cpu:
Feb 2 04:10:01 ldr kernel: CPU 0: hi: 186, btch: 31 usd: 179
Feb 2 04:10:01 ldr kernel: CPU 1: hi: 186, btch: 31 usd: 130
Feb 2 04:10:01 ldr kernel: HighMem per-cpu:
Feb 2 04:10:01 ldr kernel: CPU 0: hi: 186, btch: 31 usd: 6
Feb 2 04:10:01 ldr kernel: CPU 1: hi: 186, btch: 31 usd: 51
Feb 2 04:10:01 ldr kernel: active_anon:3208 inactive_anon:67 isolated_anon:0
Feb 2 04:10:01 ldr kernel: active_file:1330 inactive_file:3589 isolated_file:0
Feb 2 04:10:01 ldr kernel: unevictable:0 dirty:0 writeback:0 unstable:0
Feb 2 04:10:01 ldr kernel: free:290674 slab_reclaimable:1335 slab_unreclaimable:3757
Feb 2 04:10:01 ldr kernel: mapped:1448 shmem:251 pagetables:105 bounce:0
Feb 2 04:10:01 ldr kernel: free_cma:0
Feb 2 04:10:01 ldr kernel: DMA free:3388kB min:64kB low:80kB high:96kB active_anon:80kB inactive_anon:0kB active_file:0kB inactive_file:0kB unevictable:0kB isolated(anon):0kB isolated(file):0kB present:15992kB managed:15916kB mlocked:0kB dirty:0kB writeback:0kB mapped:0kB shmem:0kB slab_reclaimable:36kB slab_unreclaimable:128kB kernel_stack:16kB pagetables:4kB unstable:0kB bounce:0kB free_cma:0kB writeback_tmp:0kB pages_scanned:0 all_unreclaimable? yes
Feb 2 04:10:01 ldr kernel: lowmem_reserve[]: 0 839 1996 1996
Feb 2 04:10:01 ldr kernel: Normal free:3556kB min:3672kB low:4588kB high:5508kB active_anon:3820kB inactive_anon:56kB active_file:168kB inactive_file:284kB unevictable:0kB isolated(anon):0kB isolated(file):0kB present:892920kB managed:860136kB mlocked:0kB dirty:0kB writeback:0kB mapped:0kB shmem:72kB slab_reclaimable:5304kB slab_unreclaimable:14900kB kernel_stack:744kB pagetables:204kB unstable:0kB bounce:0kB free_cma:0kB writeback_tmp:0kB pages_scanned:749 all_unreclaimable? yes
Feb 2 04:10:01 ldr kernel: lowmem_reserve[]: 0 0 9257 9257
Feb 2 04:10:01 ldr kernel: HighMem free:1155752kB min:512kB low:1776kB high:3040kB active_anon:8932kB inactive_anon:212kB active_file:5152kB inactive_file:14072kB unevictable:0kB isolated(anon):0kB isolated(file):0kB present:1184968kB managed:1184968kB mlocked:0kB dirty:0kB writeback:0kB mapped:5792kB shmem:932kB slab_reclaimable:0kB slab_unreclaimable:0kB kernel_stack:0kB pagetables:212kB unstable:0kB bounce:0kB free_cma:0kB writeback_tmp:0kB pages_scanned:0 all_unreclaimable? no
Feb 2 04:10:01 ldr kernel: lowmem_reserve[]: 0 0 0 0
Feb 2 04:10:01 ldr kernel: DMA: 21*4kB (UE) 15*8kB (UEM) 9*16kB (UM) 9*32kB (UM) 5*64kB (UMR) 3*128kB (MR) 2*256kB (ER) 1*512kB (R) 1*1024kB (R) 0*2048kB 0*4096kB = 3388kB
Feb 2 04:10:01 ldr kernel: Normal: 333*4kB (UEM) 269*8kB (M) 0*16kB 1*32kB (R) 1*64kB (R) 0*128kB 0*256kB 0*512kB 0*1024kB 0*2048kB 0*4096kB = 3580kB
Feb 2 04:10:01 ldr kernel: HighMem: 1085*4kB (UM) 1427*8kB (UM) 1298*16kB (UM) 1116*32kB (UM) 933*64kB (UM) 723*128kB (UM) 506*256kB (UM) 280*512kB (UM) 103*1024kB (UM) 28*2048kB (UM) 121*4096kB (MR) = 1155820kB
Feb 2 04:10:01 ldr kernel: 5177 total pagecache pages
Feb 2 04:10:01 ldr kernel: 0 pages in swap cache
Feb 2 04:10:01 ldr kernel: Swap cache stats: add 0, delete 0, find 0/0
Feb 2 04:10:01 ldr kernel: Free swap = 0kB
Feb 2 04:10:01 ldr kernel: Total swap = 0kB
Feb 2 04:10:01 ldr kernel: 523470 pages RAM
Feb 2 04:10:01 ldr kernel: 296242 pages HighMem/MovableOnly
Feb 2 04:10:01 ldr kernel: 0 pages reserved
Feb 2 04:10:01 ldr kernel: [ pid ] uid tgid total_vm rss nr_ptes swapents oom_score_adj name
Feb 2 04:10:01 ldr kernel: [ 301] 0 301 807 232 3 0 0 upstart-udev-br
Feb 2 04:10:01 ldr kernel: [ 303] 0 303 768 256 3 0 -1000 udevd
Feb 2 04:10:01 ldr kernel: [ 372] 0 372 741 157 2 0 -1000 udevd
Feb 2 04:10:01 ldr kernel: [ 373] 0 373 741 152 2 0 -1000 udevd
Feb 2 04:10:01 ldr kernel: [ 795] 0 795 1172 202 3 0 0 vsftpd
Feb 2 04:10:01 ldr kernel: [ 849] 0 849 674 176 3 0 0 rpcbind
Feb 2 04:10:01 ldr kernel: [ 910] 0 910 711 66 2 0 0 upstart-socket-
Feb 2 04:10:01 ldr kernel: [ 1004] 0 1004 1670 398 3 0 -1000 sshd
Feb 2 04:10:01 ldr kernel: [ 1010] 0 1010 727 52 3 0 0 rpc.idmapd
Feb 2 04:10:01 ldr kernel: [ 1016] 102 1016 814 181 2 0 0 dbus-daemon
Feb 2 04:10:01 ldr kernel: [ 1058] 101 1058 8070 659 8 0 0 rsyslogd
Feb 2 04:10:01 ldr kernel: [ 1081] 107 1081 739 240 3 0 0 rpc.statd
Feb 2 04:10:01 ldr kernel: [ 1125] 0 1125 1038 151 4 0 0 getty
Feb 2 04:10:01 ldr kernel: [ 1132] 0 1132 1038 154 4 0 0 getty
Feb 2 04:10:01 ldr kernel: [ 1145] 0 1145 1038 152 4 0 0 getty
Feb 2 04:10:01 ldr kernel: [ 1146] 0 1146 1038 150 4 0 0 getty
Feb 2 04:10:01 ldr kernel: [ 1151] 0 1151 1038 150 4 0 0 getty
Feb 2 04:10:01 ldr kernel: [ 1160] 0 1160 640 151 2 0 0 xinetd
Feb 2 04:10:01 ldr kernel: [ 1166] 0 1166 545 102 3 0 0 acpid
Feb 2 04:10:01 ldr kernel: [ 1167] 0 1167 654 174 3 0 0 cron
Feb 2 04:10:01 ldr kernel: [ 1168] 0 1168 617 69 3 0 0 atd
Feb 2 04:10:01 ldr kernel: [ 1179] 0 1179 900 134 3 0 0 irqbalance
Feb 2 04:10:01 ldr kernel: [ 1189] 103 1189 6116 669 7 0 0 whoopsie
Feb 2 04:10:01 ldr kernel: [ 1235] 0 1235 843 176 3 0 0 rpc.mountd
Feb 2 04:10:01 ldr kernel: [ 1386] 0 1386 4937 1061 6 0 0 python
Feb 2 04:10:01 ldr kernel: [ 1387] 0 1387 535 79 3 0 0 watchdog
Feb 2 04:10:01 ldr kernel: [ 1395] 0 1395 600 139 3 0 0 getty
Feb 2 04:10:01 ldr kernel: [ 1396] 0 1396 1038 151 4 0 0 getty
Feb 2 04:10:01 ldr kernel: [ 592] 0 592 823 262 3 0 0 ldrc_script.s
Feb 2 04:10:01 ldr kernel: [ 593] 0 593 4680 710 5 0 0 python
Feb 2 04:10:01 ldr kernel: [ 594] 0 594 653 59 3 0 0 cron
Feb 2 04:10:01 ldr kernel: Out of memory: Kill process 1386 (python) score 2 or sacrifice child
Feb 2 04:10:01 ldr kernel: Killed process 593 (python) total-vm:18720kB, anon-rss:2184kB, file-rss:656kB
次の行に示すように、「正常」領域が少なくとも3672 kB下に落ちたため、ルームキラーがトリガーされたとします。
Normal free:3556kB min:3672kB low:4588kB high:5508kB active_anon:3820kB inactive_anon:56kB active_file:168kB inactive_file:284kB unevictable:0kB isolated(anon):0kB isolated(file):0kB present:892920kB managed:860136kB mlocked:0kB dirty:0kB writeback:0kB mapped:0kB shmem:72kB slab_reclaimable:5304kB slab_unreclaimable:14900kB kernel_stack:744kB pagetables:204kB unstable:0kB bounce:0kB free_cma:0kB writeback_tmp:0kB pages_scanned:749 all_unreclaimable? yes
ただし、「HighMem」領域にはまだ十分なスペースがあります。
HighMem free:1155752kB min:512kB low:1776kB high:3040kB active_anon:8932kB inactive_anon:212kB active_file:5152kB inactive_file:14072kB unevictable:0kB isolated(anon):0kB isolated(file):0kB present:1184968kB managed:1184968kB mlocked:0kB dirty:0kB writeback:0kB mapped:5792kB shmem:932kB slab_reclaimable:0kB slab_unreclaimable:0kB kernel_stack:0kB pagetables:212kB unstable:0kB bounce:0kB free_cma:0kB writeback_tmp:0kB pages_scanned:0 all_unreclaimable? no
それでは、なぜカーネルは最小値を下回るまで通常からメモリを割り当て続け、HighMemの空き領域の一部が利用可能になったときにプロセスを終了する必要がありますか？カーネルバージョンは3.14です。