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* 9.6 write time
@ 2021-12-28 16:52 Marc Millas <marc.millas@mokadb.com>
2021-12-28 17:46 ` Re: 9.6 write time Tom Lane <tgl@sss.pgh.pa.us>
0 siblings, 1 reply; 5+ messages in thread
From: Marc Millas @ 2021-12-28 16:52 UTC (permalink / raw)
To: pgsql-performance
Hi,
I am looking at a postgres 9.6 on rh7
I see that checkpoint_write_time is huge which looks quite strange as the
average amount of data written is not that big.
For example in 5:30 hours today, data from pg_stat_bgwriter view, comparing
values at 11AM and 4h30PM :
checkpoint_write_time 6986324
buffers_checkpoint 182447
so, to my understanding, it takes almost 2 hours to write 1.6 GB of data.
Can someone either correct my understanding, or shed some light on what can
cause this ??
thanks,
Marc MILLAS
Senior Architect
+33607850334
www.mokadb.com
^ permalink raw reply [nested|flat] 5+ messages in thread
* Re: 9.6 write time
2021-12-28 16:52 9.6 write time Marc Millas <marc.millas@mokadb.com>
@ 2021-12-28 17:46 ` Tom Lane <tgl@sss.pgh.pa.us>
2021-12-28 17:55 ` Re: 9.6 write time Marc Millas <marc.millas@mokadb.com>
0 siblings, 1 reply; 5+ messages in thread
From: Tom Lane @ 2021-12-28 17:46 UTC (permalink / raw)
To: Marc Millas <marc.millas@mokadb.com>; +Cc: pgsql-performance
Marc Millas <marc.millas@mokadb.com> writes:
> I am looking at a postgres 9.6 on rh7
> I see that checkpoint_write_time is huge which looks quite strange as the
> average amount of data written is not that big.
checkpoint_write_time is not the amount of time spent doing I/O;
it's the elapsed wall-clock time in the write phase. If the I/O
is being throttled because of an un-aggressive checkpoint completion
target, it could be a lot more than the actual I/O time. What have
you got your checkpoint parameters set to?
regards, tom lane
^ permalink raw reply [nested|flat] 5+ messages in thread
* Re: 9.6 write time
2021-12-28 16:52 9.6 write time Marc Millas <marc.millas@mokadb.com>
2021-12-28 17:46 ` Re: 9.6 write time Tom Lane <tgl@sss.pgh.pa.us>
@ 2021-12-28 17:55 ` Marc Millas <marc.millas@mokadb.com>
2021-12-28 18:34 ` Re: 9.6 write time Tom Lane <tgl@sss.pgh.pa.us>
0 siblings, 1 reply; 5+ messages in thread
From: Marc Millas @ 2021-12-28 17:55 UTC (permalink / raw)
To: Tom Lane <tgl@sss.pgh.pa.us>; +Cc: pgsql-performance
Hi Tom,
checkpoint completion target is 0.9
Marc MILLAS
Senior Architect
+33607850334
www.mokadb.com
On Tue, Dec 28, 2021 at 6:46 PM Tom Lane <tgl@sss.pgh.pa.us> wrote:
> Marc Millas <marc.millas@mokadb.com> writes:
> > I am looking at a postgres 9.6 on rh7
> > I see that checkpoint_write_time is huge which looks quite strange as the
> > average amount of data written is not that big.
>
> checkpoint_write_time is not the amount of time spent doing I/O;
> it's the elapsed wall-clock time in the write phase. If the I/O
> is being throttled because of an un-aggressive checkpoint completion
> target, it could be a lot more than the actual I/O time. What have
> you got your checkpoint parameters set to?
>
> regards, tom lane
>
^ permalink raw reply [nested|flat] 5+ messages in thread
* Re: 9.6 write time
2021-12-28 16:52 9.6 write time Marc Millas <marc.millas@mokadb.com>
2021-12-28 17:46 ` Re: 9.6 write time Tom Lane <tgl@sss.pgh.pa.us>
2021-12-28 17:55 ` Re: 9.6 write time Marc Millas <marc.millas@mokadb.com>
@ 2021-12-28 18:34 ` Tom Lane <tgl@sss.pgh.pa.us>
2021-12-28 18:59 ` Re: 9.6 write time Marc Millas <marc.millas@mokadb.com>
0 siblings, 1 reply; 5+ messages in thread
From: Tom Lane @ 2021-12-28 18:34 UTC (permalink / raw)
To: Marc Millas <marc.millas@mokadb.com>; +Cc: pgsql-performance
Marc Millas <marc.millas@mokadb.com> writes:
> checkpoint completion target is 0.9
checkpoint_timeout is the more interesting number here.
regards, tom lane
^ permalink raw reply [nested|flat] 5+ messages in thread
* Re: 9.6 write time
2021-12-28 16:52 9.6 write time Marc Millas <marc.millas@mokadb.com>
2021-12-28 17:46 ` Re: 9.6 write time Tom Lane <tgl@sss.pgh.pa.us>
2021-12-28 17:55 ` Re: 9.6 write time Marc Millas <marc.millas@mokadb.com>
2021-12-28 18:34 ` Re: 9.6 write time Tom Lane <tgl@sss.pgh.pa.us>
@ 2021-12-28 18:59 ` Marc Millas <marc.millas@mokadb.com>
0 siblings, 0 replies; 5+ messages in thread
From: Marc Millas @ 2021-12-28 18:59 UTC (permalink / raw)
To: Tom Lane <tgl@sss.pgh.pa.us>; +Cc: pgsql-performance
Default ie. 5 minutes
Le mar. 28 déc. 2021 à 19:34, Tom Lane <tgl@sss.pgh.pa.us> a écrit :
> Marc Millas <marc.millas@mokadb.com> writes:
> > checkpoint completion target is 0.9
>
> checkpoint_timeout is the more interesting number here.
>
> regards, tom lane
>
^ permalink raw reply [nested|flat] 5+ messages in thread
end of thread, other threads:[~2021-12-28 18:59 UTC | newest]
Thread overview: 5+ messages (download: mbox mbox.gz follow: Atom feed)
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2021-12-28 16:52 9.6 write time Marc Millas <marc.millas@mokadb.com>
2021-12-28 17:46 ` Tom Lane <tgl@sss.pgh.pa.us>
2021-12-28 17:55 ` Marc Millas <marc.millas@mokadb.com>
2021-12-28 18:34 ` Tom Lane <tgl@sss.pgh.pa.us>
2021-12-28 18:59 ` Marc Millas <marc.millas@mokadb.com>
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