Zfs heavy io writing | zfskern txg_thread_enter
Niccolò Corvini
n.corvini at gmail.com
Fri Feb 19 11:07:04 UTC 2016
Hi, first time here!
We are having a problem with a server running FreeBsd 9.1 with ZFS on a
single sata drive. Since a few days ago, in the morning the system becomes
really slow due of a really heavy io writing. We investigated and we think
it might start at night, maybe correlated to to crondaily (standard) but we
are not sure. After a few hours the situation returns to normal.
Any help is much appreciated
The machine is a Intel Xeon E5-2620 with 36GB of RAM, the HDD is a 2TB an
is half full.
gstat output:
L(q) ops/s r/s kBps ms/r w/s kBps ms/w %busy Name
13 135 21 641 256.7 108 6410 41.4 128.8| ada0
0 0 0 0 0.0 0 0 0.0 0.0| ada0p1
13 135 21 641 256.7 108 6410 41.7 128.8| ada0p2
0 0 0 0 0.0 0 0 0.0 0.0| cd0
0 0 0 0 0.0 0 0 0.0 0.0|
gptid/3c0de011-4f37-11e5-8217-3085a91c3292
0 0 0 0 0.0 0 0 0.0 0.0|
zvol/zroot/swap
13 135 21 641 256.7 108 6410 41.7 128.9| gpt/disk1
Using top -m io shows that the responsible is [zfskern{txg_thread_enter}]
top -m io output:
PID JID USERNAME VCSW IVCSW READ WRITE FAULT TOTAL PERCENT COMMAND
3 0 root 14 1 0 37 0 37 30.33%
[zfskern{txg_thread_enter}]
49866 215 7070 26 2 0 5 0 5 4.10%
postgres: stats collector process (postgres)
99901 5 70 42 0 0 4 0 4 3.28%
postgres: promeditec promeditec.osr.test 192.168.0.246(278
24820 199 www 10 0 7 0 0 7 5.74%
[jsvc{jsvc}]
33869 212 88 19 2 0 2 0 2 1.64%
[mysqld{mysqld}]
93400 0 root 13 0 10 0 0 10 8.20% [find]
89407 215 7070 10 0 0 1 0 1 0.82%
postgres: alfresco alfconservazione.dotcom.ts.it 192.168.0
15776 5 70 11 0 0 4 0 4 3.28%
postgres: stats collector process (postgres)
33869 212 88 10 0 0 3 0 3 2.46%
[mysqld{mysqld}]
33869 212 88 2 0 0 11 0 11 9.02%
[mysqld{mysqld}]
18685 198 root 5 0 0 2 0 2 1.64%
/usr/sbin/syslogd -s
15852 214 70 4 1 0 1 0 1 0.82%
postgres: alfresco alfcomunets.dotcom.ts.it 192.168.0.212(
98335 120 root 11 0 29 0 0 29 23.77% find
/var/log -name messages.* -mtime -2
16128 214 70 8 0 0 1 0 1 0.82%
postgres: alfresco alfaxErre8 192.168.0.208(50558) (postg
1116 198 root 10 0 0 1 0 1 0.82%
sendmail: ./u1J9k90d001112 local: client DATA status (send
1120 198 root 7 0 0 4 0 4 3.28%
mail.local -l
Using procstat -kk on the zfskern pid shows:
PID TID COMM TDNAME KSTACK
3 100129 zfskern arc_reclaim_thre mi_switch sleepq_timedwait
_cv_timedwait arc_reclaim_thread fork_exit fork_trampoline
3 100130 zfskern l2arc_feed_threa mi_switch sleepq_timedwait
_cv_timedwait l2arc_feed_thread fork_exit fork_trampoline
3 100504 zfskern txg_thread_enter mi_switch sleepq_wait
_cv_wait txg_thread_wait txg_quiesce_thread fork_exit fork_trampoline
3 100505 zfskern txg_thread_enter mi_switch sleepq_wait
_cv_wait zio_wait dsl_pool_sync spa_sync txg_sync_thread fork_exit
fork_trampoline
3 100506 zfskern zvol zroot/swap mi_switch sleepq_wait _sleep
zvol_geom_worker fork_exit fork_trampoline
systat -vmstat
7 users Load 0.50 0.62 1.46 Feb 19 11:46
Mem:KB REAL VIRTUAL VN PAGER SWAP
PAGER
Tot Share Tot Share Free in out in
out
Act 41318k 199492 1251183k 588716 2254748 count
All 46844k 229048 -1968M 892088 pages
Proc: Interrupts
r p d s w Csw Trp Sys Int Sof Flt cow 2836 total
4k 8516 393 12k 236 1445 11k 11281 zfod
atkbd0 1
ozfod acpi0
9
4.4%Sys 0.0%Intr 0.3%User 0.0%Nice 95.4%Idle %ozfod ehci0
17
| | | | | | | | | | | daefr ehci1
23
== 11171 prcfr 79
cpu0:timer
dtbuf 11265 totfr isci0
264
Namei Name-cache Dir-cache 1095774 desvn react 24
em0:rx 0
Calls hits % hits % 409282 numvn pdwak 16
em0:tx 0
78 41 53 273943 frevn pdpgs
em0:link
intrn 196 ahci0
278
Disks ada0 cd0 pass0 pass1 20445132 wire 267
cpu21:time
KB/t 2.55 0.00 0.00 0.00 37317552 act 55
cpu13:time
tps 223 0 0 0 4948708 inact 86
cpu5:timer
MB/s 0.56 0.00 0.00 0.00 884804 cache 24
cpu12:time
%busy 94 0 0 0 1370012 free 63
cpu10:time
buf 306
cpu19:time
63
cpu11:time
55
cpu14:time
86
cpu9:timer
71
cpu18:time
86
cpu3:timer
47
cpu23:time
55
cpu6:timer
55
cpu22:time
71
cpu2:timer
39
cpu20:time
zpool status:
pool: zroot
state: ONLINE
scan: scrub repaired 0 in 3h46m with 0 errors on Wed Nov 4 21:54:44 2015
config:
NAME STATE READ WRITE CKSUM
zroot ONLINE 0 0 0
gpt/disk1 ONLINE 0 0 0
errors: No known data errors
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