Re: Parallel Seq Scan vs kernel read ahead - Mailing list pgsql-hackers

From Thomas Munro
Subject Re: Parallel Seq Scan vs kernel read ahead
Date
Msg-id CA+hUKGKKhdSNPO1a5xe=HkeUpvsFCsODOib-fDDsi1+aDR+XWQ@mail.gmail.com
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In response to Re: Parallel Seq Scan vs kernel read ahead  (Ranier Vilela <ranier.vf@gmail.com>)
Responses Re: Parallel Seq Scan vs kernel read ahead
List pgsql-hackers
On Thu, May 21, 2020 at 1:38 PM Ranier Vilela <ranier.vf@gmail.com> wrote:
>> >> On Thu, May 21, 2020 at 11:15 AM Ranier Vilela <ranier.vf@gmail.com> wrote:
>> >> > postgres=# set max_parallel_workers_per_gather = 0;
>> >> > Time: 227238,445 ms (03:47,238)
>> >> > postgres=# set max_parallel_workers_per_gather = 1;
>> >> > Time: 138027,351 ms (02:18,027)

> Vanila Postgres (latest)
>
> create table t as select generate_series(1, 800000000)::int i;
>  set max_parallel_workers_per_gather = 0;
> Time: 210524,317 ms (03:30,524)
> set max_parallel_workers_per_gather = 1;
> Time: 146982,737 ms (02:26,983)

Thanks.  So it seems like Linux, Windows and anything using ZFS are
OK, which probably explains why we hadn't heard complaints about it.



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