| From: | Ants Aasma <ants(at)cybertec(dot)at> |
|---|---|
| To: | Andres Freund <andres(at)2ndquadrant(dot)com> |
| Cc: | Robert Haas <robertmhaas(at)gmail(dot)com>, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>, Heikki Linnakangas <hlinnakangas(at)vmware(dot)com>, Claudio Freire <klaussfreire(at)gmail(dot)com>, Fabien COELHO <coelho(at)cri(dot)ensmp(dot)fr>, Josh Berkus <josh(at)agliodbs(dot)com>, PostgreSQL Developers <pgsql-hackers(at)postgresql(dot)org> |
| Subject: | Re: postgresql latency & bgwriter not doing its job |
| Date: | 2014-09-04 07:09:30 |
| Message-ID: | CA+CSw_uM-sUbs1cb1Pr--wbrgjuuCm+4qvbozhX2o_+zFLW8bA@mail.gmail.com |
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On Thu, Sep 4, 2014 at 12:36 AM, Andres Freund <andres(at)2ndquadrant(dot)com> wrote:
> It's imo quite clearly better to keep it allocated. For one after
> postmaster started the checkpointer successfully you don't need to be
> worried about later failures to allocate memory if you allocate it once
> (unless the checkpointer FATALs out which should be exceedingly rare -
> we're catching ERRORs). It's much much more likely to succeed
> initially. Secondly it's not like there's really that much time where no
> checkpointer isn't running.
In principle you could do the sort with the full sized array and then
compress it to a list of buffer IDs that need to be written out. This
way most of the time you only need a small array and the large array
is only needed for a fraction of a second.
Regards,
Ants Aasma
--
Cybertec Schönig & Schönig GmbH
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A-2700 Wiener Neustadt
Web: http://www.postgresql-support.de
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