O que está usando todo o meu cache e por que não consigo apagá-lo?
Não estou tentando otimizar o desempenho ou ajustar o sistema, a melhor descrição é que esse é um exercício de compreensão e aprendizado, e estou pedindo para que possamos segui-lo.
Executando o kernel 4.16.13-200.fc27.x86_64
Se eu executar o seguinte comando (que produz a seguinte saída)
free;sync;free; echo 3 > /proc/sys/vm/drop_caches;free
total used free shared buff/cache available
Mem: 16276472 259676 7034800 59720 8981996 8502360
Swap: 0 0 0
total used free shared buff/cache available
Mem: 16276472 259792 7034652 59720 8982028 8502228
Swap: 0 0 0
total used free shared buff/cache available
Mem: 16276472 259748 7036492 59720 8980232 8502948
Swap: 0 0 0
Espero que o valor do buff / cache seja bem baixo, certamente muito menor que cerca de 9 GB.
Eu só tenho os seguintes processos que não são [sistema] em execução:
ps -ef | grep -v \[
UID PID PPID C STIME TTY TIME CMD
root 1 0 0 Jul23 ? 00:03:52 /usr/lib/systemd/systemd --switched-root --system --deserialize 24
dbus 1136 1 0 Jul23 ? 00:06:30 /usr/bin/dbus-daemon --system --address=systemd: --nofork --nopidfile --systemd-activation --syslog-only
root 1245 1 0 Jul23 ? 00:00:01 /usr/sbin/sshd -D [email protected],[email protected],aes256-ctr,aes256-cbc,[email protected],aes128-ctr,aes128-cbc,3des-cbc [email protected],[email protected],[email protected],[email protected],[email protected],hmac-sha1,hmac-sha2-256,hmac-sha2-512 -oGSSAPIKexAlgorithms=gss-gex-sha1-,gss-group14-sha1- [email protected],ecdh-sha2-nistp256,ecdh-sha2-nistp384,ecdh-sha2-nistp521,diffie-hellman-group-exchange-sha256,diffie-hellman-group-exchange-sha1,diffie-hellman-group14-sha1
root 1395 1 0 Jul23 ? 00:02:02 /usr/lib/systemd/systemd-logind
root 1396 1 0 Jul23 ? 00:00:55 /usr/libexec/accounts-daemon
root 1609 1607 0 21:39 ? 00:00:00 sshd: root@pts/5
root 1610 1609 0 21:39 pts/5 00:00:00 -zsh
root 1642 1640 0 21:39 ? 00:00:00 sshd: root@pts/0
root 1643 1642 0 21:39 pts/0 00:00:01 -zsh
root 1668 1665 0 21:40 ? 00:00:00 sshd: root@pts/2
root 1669 1668 0 21:40 pts/2 00:00:00 -zsh
root 1719 1 0 Jul23 tty1 00:00:00 /sbin/agetty -o -p -- \u --noclear tty1 linux
root 2601 1 0 21:47 ? 00:00:00 /usr/lib/systemd/systemd-udevd
root 2685 1669 0 21:55 pts/2 00:00:00 ps -ef
root 13104 13025 0 18:05 ? 00:00:00 sshd: root@pts/1
root 14359 1 0 Jul23 ? 00:00:00 /usr/lib/systemd/systemd --user
root 14360 14359 0 Jul23 ? 00:00:00 (sd-pam)
root 28017 13104 0 21:28 pts/1 00:00:00 -zsh
root 28050 28017 0 21:28 pts/1 00:00:03 top
e o topo classificado pelo uso de RAM mostra:
top - 22:01:59 up 2 days, 13:59, 4 users, load average: 0.00, 0.00, 0.02
Tasks: 125 total, 1 running, 69 sleeping, 0 stopped, 0 zombie
%Cpu(s): 0.0 us, 0.1 sy, 0.0 ni, 99.8 id, 0.0 wa, 0.0 hi, 0.1 si, 0.0 st
KiB Mem : 16276472 total, 7033768 free, 258980 used, 8983724 buff/cache
KiB Swap: 0 total, 0 free, 0 used. 8502072 avail Mem
PID USER PR NI VIRT RES SHR S %CPU %MEM TIME+ COMMAND
1640 root 20 0 148024 8320 7216 S 0.0 0.1 0:00.05 sshd
13025 root 20 0 148024 8312 7212 S 0.0 0.1 0:00.01 sshd
1665 root 20 0 148024 8220 7116 S 0.0 0.1 0:00.06 sshd
1607 root 20 0 148024 8080 6972 S 0.0 0.0 0:00.03 sshd
2601 root 20 0 97684 7332 5904 S 0.0 0.0 0:00.06 systemd-udevd
1 root 20 0 228444 7884 4944 S 0.0 0.0 3:52.62 systemd
1245 root 20 0 82792 5536 4708 S 0.0 0.0 0:01.97 sshd
1610 root 20 0 164076 11060 4228 S 0.0 0.1 0:00.09 zsh
28017 root 20 0 164076 11016 4184 S 0.0 0.1 0:00.04 zsh
1669 root 20 0 168436 11336 4164 S 0.0 0.1 0:00.60 zsh
1643 root 20 0 164076 10928 4016 S 0.0 0.1 0:02.00 zsh
cat /proc/vmstat
nr_free_pages 1758411
nr_zone_inactive_anon 17180
nr_zone_active_anon 9584
nr_zone_inactive_file 1049
nr_zone_active_file 4853
nr_zone_unevictable 0
nr_zone_write_pending 1
nr_mlock 0
nr_page_table_pages 1036
nr_kernel_stack 2080
nr_bounce 0
nr_zspages 0
nr_free_cma 0
numa_hit 3000299470
numa_miss 0
numa_foreign 0
numa_interleave 21375
numa_local 3000299470
numa_other 0
nr_inactive_anon 17180
nr_active_anon 9584
nr_inactive_file 1049
nr_active_file 4853
nr_unevictable 0
nr_slab_reclaimable 427423
nr_slab_unreclaimable 1797722
nr_isolated_anon 0
nr_isolated_file 0
workingset_refault 19330098
workingset_activate 3316794
workingset_nodereclaim 1045284
nr_anon_pages 11842
nr_mapped 4365
nr_file_pages 20844
nr_dirty 5
nr_writeback 0
nr_writeback_temp 0
nr_shmem 14930
nr_shmem_hugepages 0
nr_shmem_pmdmapped 0
nr_anon_transparent_hugepages 0
nr_unstable 0
nr_vmscan_write 526329
nr_vmscan_immediate_reclaim 47959
nr_dirtied 90587620
nr_written 90117830
nr_dirty_threshold 344348
nr_dirty_background_threshold 171963
pgpgin 329849668
pgpgout 656116433
pswpin 311639
pswpout 526807
pgalloc_dma 12
pgalloc_dma32 473350531
pgalloc_normal 2600312635
pgalloc_movable 0
allocstall_dma 0
allocstall_dma32 0
allocstall_normal 2594
allocstall_movable 7924
pgskip_dma 0
pgskip_dma32 0
pgskip_normal 0
pgskip_movable 0
pgfree 3087941289
pgactivate 31241868
pgdeactivate 54808523
pglazyfree 165199
pgfault 3727210961
pgmajfault 376546
pglazyfreed 88855
pgrefill 56262502
pgsteal_kswapd 93158250
pgsteal_direct 5218459
pgscan_kswapd 94863466
pgscan_direct 5274174
pgscan_direct_throttle 0
zone_reclaim_failed 0
pginodesteal 1983292
slabs_scanned 150018640
kswapd_inodesteal 13603030
kswapd_low_wmark_hit_quickly 37060
kswapd_high_wmark_hit_quickly 1617
pageoutrun 91741
pgrotated 582111
drop_pagecache 82
drop_slab 82
oom_kill 0
numa_pte_updates 0
numa_huge_pte_updates 1
numa_hint_faults 0
numa_hint_faults_local 0
numa_pages_migrated 0
pgmigrate_success 12440716
pgmigrate_fail 2270900
compact_migrate_scanned 356381883
compact_free_scanned 1233511266
compact_isolated 27255306
compact_stall 1024
compact_fail 793
compact_success 231
compact_daemon_wake 75068
compact_daemon_migrate_scanned 315527488
compact_daemon_free_scanned 936465547
htlb_buddy_alloc_success 0
htlb_buddy_alloc_fail 0
unevictable_pgs_culled 11829
unevictable_pgs_scanned 0
unevictable_pgs_rescued 14
unevictable_pgs_mlocked 14
unevictable_pgs_munlocked 8
unevictable_pgs_cleared 6
unevictable_pgs_stranded 0
thp_fault_alloc 6978
thp_fault_fallback 327
thp_collapse_alloc 405
thp_collapse_alloc_failed 3405
thp_file_alloc 0
thp_file_mapped 0
thp_split_page 0
thp_split_page_failed 0
thp_deferred_split_page 7280
thp_split_pmd 1
thp_split_pud 0
thp_zero_page_alloc 0
thp_zero_page_alloc_failed 0
thp_swpout 1
thp_swpout_fallback 0
balloon_inflate 0
balloon_deflate 0
balloon_migrate 0
swap_ra 184300
swap_ra_hit 166308
Eu até tentei:
echo 1000 > /proc/sys/vm/vfs_cache_pressure
e
echo 5000000 > /proc/sys/vm/min_free_kbytes
mas mesmo assim, depois de echo 3 > /proc/sys/vm/drop_caches que não faz nada para o cache ainda deixando cerca de 9GB de cache em uso
O que está usando todo o meu cache e por que não consigo me livrar dele?
Eu deixei o sistema como o acima (ao lado de nada em execução, o cache não é apagado manualmente) por cerca de 10 horas (durante a noite) e, durante esse período, o cache caiu para o tamanho imediatamente após a reinicialização.
total used free shared buff/cache available
Mem: 16276472 245420 15454540 59704 576512 14101780
Isso ainda me deixa com o problema original - O que está usando todo o meu cache e por que não posso me livrar dele?