| From: | Claudio Freire <klaussfreire(at)gmail(dot)com> |
|---|---|
| To: | Masahiko Sawada <sawada(dot)mshk(at)gmail(dot)com> |
| Cc: | Michael Paquier <michael(dot)paquier(at)gmail(dot)com>, Robert Haas <robertmhaas(at)gmail(dot)com>, Pavan Deolasee <pavan(dot)deolasee(at)gmail(dot)com>, Amit Kapila <amit(dot)kapila16(at)gmail(dot)com>, PostgreSQL-development <pgsql-hackers(at)postgresql(dot)org> |
| Subject: | Re: Block level parallel vacuum WIP |
| Date: | 2017-01-06 22:18:45 |
| Message-ID: | CAGTBQpaTOHfhVhQ=pCxCPM_2wTpb-EUk3vYXP4jR2QiVb2-dHA@mail.gmail.com |
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| Lists: | pgsql-hackers |
On Fri, Jan 6, 2017 at 2:38 PM, Masahiko Sawada <sawada(dot)mshk(at)gmail(dot)com> wrote:
> table_size | indexes | parallel_degree | time
> ------------+---------+-----------------+----------
> 6.5GB | 0 | 1 | 00:00:14
> 6.5GB | 0 | 2 | 00:00:02
> 6.5GB | 0 | 4 | 00:00:02
Those numbers look highly suspect.
Are you sure you're not experiencing caching effects? (ie: maybe you
ran the second and third vacuums after the first, and didn't flush the
page cache, so the table was cached)
> 6.5GB | 2 | 1 | 00:02:18
> 6.5GB | 2 | 2 | 00:00:38
> 6.5GB | 2 | 4 | 00:00:46
...
> 13GB | 0 | 1 | 00:03:52
> 13GB | 0 | 2 | 00:00:49
> 13GB | 0 | 4 | 00:00:50
..
> 13GB | 2 | 1 | 00:12:42
> 13GB | 2 | 2 | 00:01:17
> 13GB | 2 | 4 | 00:02:12
These would also be consistent with caching effects
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