From: | Jehan-Guillaume de Rorthais <ioguix(at)free(dot)fr> |
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To: | Artem Tomyuk <admin(at)leboutique(dot)com>,pgsql-admin(at)postgresql(dot)org,pgsql-performance(at)postgresql(dot)org |
Subject: | Re: [ADMIN] autovacuum disk IO |
Date: | 2016-03-04 17:28:02 |
Message-ID: | E21C588F-71A9-4CBF-B396-647FF7628B11@free.fr |
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Lists: | pgsql-admin pgsql-performance |
Le 2 mars 2016 16:25:10 GMT+01:00, Artem Tomyuk <admin(at)leboutique(dot)com> a écrit :
>Hi.
>
>I've noticed that autovac. process worked more than 10 minutes, during
>this
>zabbix logged more than 90% IO disk utilization on db volume....
>
>===========>29237 2016-03-02 15:17:23 EET 00000 [24-1]LOG:
>automatic vacuum of table "lb_upr.public._reference32": index scans: 1
> pages: 0 removed, 263307 remain
> tuples: 298 removed, 1944753 remain, 0 are dead but not yet removable
> buffer usage: 67814 hits, 265465 misses, 15647 dirtied
> avg read rate: 3.183 MB/s, avg write rate: 0.188 MB/s
According to what I am reading here, your autovacumm avg read activity was less than 4MB/s...and 188kB/s for writes.
I seriously doubt these numbers are high enough to saturate your disks bandwidth.
> *system usage: CPU 5.34s/6.27u sec elapsed 651.57 sec*
This tells that the autovacumm tooks 651s to complete...but only 5s and 6s of cpu in kernel and userland in total.
Autovacuum are slowed down thanks to autovacumm_vacuum_cost_delay param, which explains the 10min run and such a low disk activity.
>Is it possible to log autovac. io impact during it execution?
I would bet the problem is elsewhere...
/Ioguix
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