public inbox for [email protected]
help / color / mirror / Atom feedFrom: David Rowley <[email protected]>
To: Nathan Bossart <[email protected]>
Cc: Sami Imseih <[email protected]>
Cc: Robert Haas <[email protected]>
Cc: Jeremy Schneider <[email protected]>
Cc: [email protected]
Subject: Re: another autovacuum scheduling thread
Date: Sat, 1 Nov 2025 16:29:30 +1300
Message-ID: <CAApHDvoCFQxaQjUncTAtCRFAeANe2tpc-WCkJue=FaXRYOkV=Q@mail.gmail.com> (raw)
In-Reply-To: <CAApHDvqe7ee=vobWe4GVAt2gm_H6eiGNZeo_dEMptvHYAkibBA@mail.gmail.com>
References: <CAApHDvoM5MEHHBc0TNdrzkpq39WdEHSZhdWrtnx9zOWNXTSFGw@mail.gmail.com>
<aP-YgrcPi0EhgR9x@nathan>
<CAApHDvpOq09uVq7aXcuSBPAhZBTfAL-m2c4FOF2PphFe-YcnRg@mail.gmail.com>
<aQEvm40W3aVizp5Q@nathan>
<CAA5RZ0sdhUjVVKYbBGs1qFsYC3-Mn+as=K5v8ydVGR5iziabFQ@mail.gmail.com>
<aQI39ln_jZ8qorLE@nathan>
<CA+Tgmoa_5aC0w1fG7pLhev+F-GtRhQ2OzePy7t059c9JTnvjow@mail.gmail.com>
<aQPSYD11NDoREZsg@nathan>
<CAA5RZ0uo-nU9KqgXV5Tcf8aWWQkxsb5BDpkb-2Qfwbw-UVVaUA@mail.gmail.com>
<CAA5RZ0tpV3PRHejTGG5-LSsqNKKV0qP=SDvurs8wj7pTk7jYJw@mail.gmail.com>
<aQUYP1WjrEP3buQz@nathan>
<CAApHDvqe7ee=vobWe4GVAt2gm_H6eiGNZeo_dEMptvHYAkibBA@mail.gmail.com>
On Sat, 1 Nov 2025 at 14:50, David Rowley <[email protected]> wrote:
> If we logged the score, we could do the "unpatched" test with the
> patched code, just with commenting out the
> list_sort(tables_to_process, TableToProcessComparator); It'd then be
> interesting to zero the log_auto*_min_duration settings and review the
> order differences and how high the scores got. Would the average score
> be higher or lower with patched version? I'd guess lower since the
> higher scoring tables would tend to get vacuumed later with the
> unpatched version and their score would be even higher by the time
> autovacuum got to them. I think if the average score has gone down at
> the point that the vacuum starts, then that's a very good thing. Maybe
> we'd need to write a patch to recalculate the "tables_to_process" List
> after a table is vacuumed and autovacuum_naptime has elapsed for us to
> see this, else the priorities might have become too outdated. I'd
> expect that to be even more true when vacuum_cost_limit is configured
> too low.
I'm not yet sure how meaningful it is, but I tried adding the
following to recheck_relation_needs_vacanalyze():
elog(LOG, "Performing autovacuum of table \"%s\" with score = %f",
get_rel_name(relid), score);
then after grepping the logs and loading the data into a table and performing:
select case patched when true then 'v7' else 'master' end as
patched,case when left(tab, 11) = 'table_batch' then 'table_batch_*'
when left(tab,6) = 'table_' then 'table_*' else 'other' end,
avg(score) as avg_Score,count(*) as count from autovac where score>0
and score<2000 group by rollup(1,2) order by 2,1;
with vacuum_cost_limit = 5000, I got:
patched | case | avg_score | count
---------+---------------+--------------------+-------
master | other | 2.004997014705882 | 68
v7 | other | 1.9668087323943668 | 71
master | table_* | 1.196698981375357 | 1396
v7 | table_* | 1.2134741693430646 | 1370
master | table_batch_* | 2.1887380086206902 | 116
v7 | table_batch_* | 1.8882025693430664 | 137
master | | 1.3043197367088595 | 1580
v7 | | 1.3059485323193893 | 1578
| | 1.3051336187460454 | 3158
It would still be good to do the rate limiting as there's more work
being done in the patched version. Seems to be about 1.1% more rows in
batch_tables and 0.48% more updates in the numbered_tables in the
patched version.
David
view thread (143+ messages) latest in thread
reply
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Reply to all the recipients using the --to and --cc options:
reply via email
To: [email protected]
Cc: [email protected], [email protected], [email protected], [email protected], [email protected]
Subject: Re: another autovacuum scheduling thread
In-Reply-To: <CAApHDvoCFQxaQjUncTAtCRFAeANe2tpc-WCkJue=FaXRYOkV=Q@mail.gmail.com>
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
This inbox is served by agora; see mirroring instructions
for how to clone and mirror all data and code used for this inbox