There is a piece of log from /var/log/messages about OOM:
Apr 15 10:46:50 localhost kernel: ls invoked oom-killer: gfp_mask=0x201da, order=0, oom_score_adj=0
Apr 15 10:46:50 localhost kernel: ls cpuset=/ mems_allowed=0
Apr 15 10:46:50 localhost kernel: CPU: 1 PID: 28654 Comm: ls Kdump: loaded Not tainted 3.10.0-1160.21.1.el7.x86_64 #1
Apr 15 10:46:50 localhost kernel: Hardware name: Bochs Bochs, BIOS rel-1.7.5.1-20190822_073655 04/01/2014
Apr 15 10:46:50 localhost kernel: Call Trace:
Apr 15 10:46:50 localhost kernel: [<ffffffff90d8305a>] dump_stack+0x19/0x1b
Apr 15 10:46:50 localhost kernel: [<ffffffff90d7d97a>] dump_header+0x90/0x229
Apr 15 10:46:50 localhost kernel: [<ffffffff9090eb3b>] ? cred_has_capability+0x6b/0x120
Apr 15 10:46:50 localhost kernel: [<ffffffff907c221d>] oom_kill_process+0x2cd/0x490
Apr 15 10:46:50 localhost kernel: [<ffffffff9090ec1e>] ? selinux_capable+0x2e/0x40
Apr 15 10:46:50 localhost kernel: [<ffffffff907c290a>] out_of_memory+0x31a/0x500
Apr 15 10:46:50 localhost kernel: [<ffffffff90d7e497>] __alloc_pages_slowpath+0x5db/0x729
Apr 15 10:46:50 localhost kernel: [<ffffffff907c8e86>] __alloc_pages_nodemask+0x436/0x450
Apr 15 10:46:50 localhost kernel: [<ffffffff90818b58>] alloc_pages_current+0x98/0x110
Apr 15 10:46:50 localhost kernel: [<ffffffff907bdcd7>] __page_cache_alloc+0x97/0xb0
Apr 15 10:46:50 localhost kernel: [<ffffffff907c0c70>] filemap_fault+0x270/0x420
Apr 15 10:46:50 localhost kernel: [<ffffffffc029791e>] __xfs_filemap_fault+0x7e/0x1d0 [xfs]
Apr 15 10:46:50 localhost kernel: [<ffffffffc0297b1c>] xfs_filemap_fault+0x2c/0x30 [xfs]
Apr 15 10:46:50 localhost kernel: [<ffffffff907edf5a>] __do_fault.isra.61+0x8a/0x100
Apr 15 10:46:50 localhost kernel: [<ffffffff907ee50c>] do_read_fault.isra.63+0x4c/0x1b0
Apr 15 10:46:50 localhost kernel: [<ffffffff907f5d50>] handle_mm_fault+0xa20/0xfb0
Apr 15 10:46:50 localhost kernel: [<ffffffff90d90653>] __do_page_fault+0x213/0x500
Apr 15 10:46:50 localhost kernel: [<ffffffff90d90a26>] trace_do_page_fault+0x56/0x150
Apr 15 10:46:50 localhost kernel: [<ffffffff90d8ffa2>] do_async_page_fault+0x22/0xf0
Apr 15 10:46:50 localhost kernel: [<ffffffff90d8c7a8>] async_page_fault+0x28/0x30
Apr 15 10:46:50 localhost kernel: Mem-Info:
Apr 15 10:46:50 localhost kernel: active_anon:7548052 inactive_anon:137382 isolated_anon:0#012 active_file:38 inactive_file:1482 isolated_file:31#012 unevictable:0 dirty:0 writeback:0 unstable:0#012 slab_reclaimable:92639 slab_unreclaimable:14747#012 mapped:10563 shmem:405626 pagetables:47771 bounce:0#012 free:49990 free_pcp:143 free_cma:0
Apr 15 10:46:50 localhost kernel: Node 0 DMA free:15892kB min:32kB low:40kB high:48kB active_anon:0kB inactive_anon:0kB active_file:0kB inactive_file:0kB unevictable:0kB isolated(anon):0kB isolated(file):0kB present:15992kB managed:15908kB mlocked:0kB dirty:0kB writeback:0kB mapped:0kB shmem:0kB slab_reclaimable:0kB slab_unreclaimable:16kB kernel_stack:0kB pagetables:0kB unstable:0kB bounce:0kB free_pcp:0kB local_pcp:0kB free_cma:0kB writeback_tmp:0kB pages_scanned:0 all_unreclaimable? yes
Apr 15 10:46:50 localhost kernel: lowmem_reserve[]: 0 2829 31991 31991
Apr 15 10:46:50 localhost kernel: Node 0 DMA32 free:122524kB min:5972kB low:7464kB high:8956kB active_anon:2526928kB inactive_anon:45416kB active_file:0kB inactive_file:1760kB unevictable:0kB isolated(anon):0kBisolated(file):0kB present:3129216kB managed:2897760kB mlocked:0kB dirty:0kB writeback:0kB mapped:4980kB shmem:146248kB slab_reclaimable:152112kB slab_unreclaimable:10172kB kernel_stack:816kB pagetables:17280kBunstable:0kB bounce:0kB free_pcp:196kB local_pcp:0kB free_cma:0kB writeback_tmp:0kB pages_scanned:2018 all_unreclaimable? no
Apr 15 10:46:50 localhost kernel: lowmem_reserve[]: 0 0 29161 29161
Apr 15 10:46:50 localhost kernel: Node 0 Normal free:61544kB min:61572kB low:76964kB high:92356kB active_anon:27665280kB inactive_anon:504112kB active_file:204kB inactive_file:4168kB unevictable:0kB isolated(anon):0kB isolated(file):0kB present:30408704kB managed:29864624kB mlocked:0kB dirty:0kB writeback:0kB mapped:37272kB shmem:1476256kB slab_reclaimable:218444kB slab_unreclaimable:48800kB kernel_stack:3904kB pagetables:173804kB unstable:0kB bounce:0kB free_pcp:376kB local_pcp:0kB free_cma:0kB writeback_tmp:0kB pages_scanned:4913 all_unreclaimable? no
Apr 15 10:46:50 localhost kernel: lowmem_reserve[]: 0 0 0 0
Apr 15 10:46:50 localhost kernel: Node 0 DMA: 1*4kB (U) 0*8kB 1*16kB (U) 0*32kB 2*64kB (U) 1*128kB (U) 1*256kB (U) 0*512kB 1*1024kB (U) 1*2048kB (M) 3*4096kB (M) = 15892kB
Apr 15 10:46:50 localhost kernel: Node 0 DMA32: 1095*4kB (UE) 809*8kB (UE) 1696*16kB (UEM) 2060*32kB (UEM) 200*64kB (UEM) 31*128kB (UE) 10*256kB (U) 0*512kB 0*1024kB 0*2048kB 0*4096kB = 123236kB
Apr 15 10:46:50 localhost kernel: Node 0 Normal: 1511*4kB (UE) 1466*8kB (UEM) 1149*16kB (UEM) 469*32kB (UEM) 126*64kB (UEM) 27*128kB (UEM) 2*256kB (UM) 0*512kB 0*1024kB 0*2048kB 0*4096kB = 63196kB
Apr 15 10:46:50 localhost kernel: Node 0 hugepages_total=0 hugepages_free=0 hugepages_surp=0 hugepages_size=2048kB
Apr 15 10:46:50 localhost kernel: 407831 total pagecache pages
Apr 15 10:46:50 localhost kernel: 0 pages in swap cache
Apr 15 10:46:50 localhost kernel: Swap cache stats: add 0, delete 0, find 0/0
Apr 15 10:46:50 localhost kernel: Free swap = 0kB
Apr 15 10:46:50 localhost kernel: Total swap = 0kB
Apr 15 10:46:50 localhost kernel: 8388478 pages RAM
Apr 15 10:46:50 localhost kernel: 0 pages HighMem/MovableOnly
Apr 15 10:46:50 localhost kernel: 193905 pages reserved
Apr 15 10:46:50 localhost kernel: [ pid ] uid tgid total_vm rss nr_ptes swapents oom_score_adj name
Apr 15 10:46:50 localhost kernel: [ 471] 0 471 31363 12826 67 0 0 systemd-journal
Apr 15 10:46:50 localhost kernel: [ 499] 0 499 12158 559 26 0 -1000 systemd-udevd
Apr 15 10:46:50 localhost kernel: [ 638] 0 638 13883 112 26 0 -1000 auditd
Apr 15 10:46:50 localhost kernel: [ 665] 999 665 153256 2291 61 0 0 polkitd
Apr 15 10:46:50 localhost kernel: [ 668] 81 668 16571 152 33 0 -900 dbus-daemon
Apr 15 10:46:50 localhost kernel: [ 674] 998 674 30147 122 29 0 0 chronyd
Apr 15 10:46:50 localhost kernel: [ 750] 0 750 6596 75 19 0 0 systemd-logind
Apr 15 10:46:50 localhost kernel: [ 793] 0 793 31598 160 17 0 0 crond
Apr 15 10:46:50 localhost kernel: [ 908] 0 908 89710 5621 97 0 0 firewalld
Apr 15 10:46:50 localhost kernel: [ 2765] 0 2765 143572 2831 97 0 0 tuned
Apr 15 10:46:50 localhost kernel: [ 2770] 0 2770 173343 8717 182 0 0 rsyslogd
Apr 15 10:46:50 localhost kernel: [ 2827] 0 2827 27552 34 10 0 0 agetty
Apr 15 10:46:50 localhost kernel: [ 2862] 0 2862 6117 115 16 0 -1000 sshd
Apr 15 10:46:50 localhost kernel: [ 3133] 0 3133 22436 260 42 0 0 master
Apr 15 10:46:50 localhost kernel: [ 3136] 89 3136 22479 256 45 0 0 qmgr
Apr 15 10:46:50 localhost kernel: [29274] 0 29274 6967 283 19 0 0 sshd
Apr 15 10:46:50 localhost kernel: [24872] 0 24872 5988 95 16 0 0 sftp-server
Apr 15 10:46:50 localhost kernel: [13398] 0 13398 6845 130 18 0 0 sshd
Apr 15 10:46:50 localhost kernel: [16576] 0 16576 28887 104 13 0 0 bash
Apr 15 10:46:50 localhost kernel: [12019] 0 12019 6738 1290 18 0 0 tmux
Apr 15 10:46:50 localhost kernel: [12020] 0 12020 28887 116 13 0 0 bash
Apr 15 10:46:50 localhost kernel: [31979] 0 31979 40558 208 36 0 0 top
Apr 15 10:46:50 localhost kernel: [15285] 0 15285 72341147 7258379 46500 0 0 dgraph
Apr 15 10:46:50 localhost kernel: [14476] 0 14476 28887 100 13 0 0 bash
Apr 15 10:46:50 localhost kernel: [14980] 0 14980 5011 69 15 0 0 tmux
Apr 15 10:46:50 localhost kernel: [ 3844] 89 3844 22462 252 44 0 0 pickup
Apr 15 10:46:50 localhost kernel: [25393] 0 25393 27014 19 10 0 0 sleep
Apr 15 10:46:50 localhost kernel: [27707] 0 27707 27014 19 9 0 0 sleep
Apr 15 10:46:50 localhost kernel: [27710] 0 27710 27014 18 10 0 0 sleep
Apr 15 10:46:50 localhost kernel: [28642] 0 28642 27014 24 10 0 0 sleep
Apr 15 10:46:50 localhost kernel: [28645] 0 28645 27014 24 10 0 0 sleep
Apr 15 10:46:50 localhost kernel: [28650] 0 28650 27014 23 9 0 0 sleep
Apr 15 10:46:50 localhost kernel: [28653] 0 28653 4853 37 14 0 0 ls
Apr 15 10:46:50 localhost kernel: [28654] 0 28654 4853 38 13 0 0 ls
Apr 15 10:46:50 localhost kernel: [28655] 0 28655 27014 22 9 0 0 sleep
Apr 15 10:46:50 localhost kernel: Out of memory: Kill process 15285 (dgraph) score 864 or sacrifice child
Apr 15 10:46:50 localhost kernel: Killed process 15285 (dgraph), UID 0, total-vm:289364588kB, anon-rss:29033516kB, file-rss:0kB, shmem-rss:0kB
yes i use 21.03
centos 7.6 / 20 Core / 48G memery / 2T ssd storage
the rdf dataset approximately 700G .