| From: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
|---|---|
| To: | Andres Freund <andres(at)2ndquadrant(dot)com> |
| Cc: | 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: | 2014-08-30 18:16:10 |
| Message-ID: | 7226.1409422570@sss.pgh.pa.us |
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| Lists: | pgsql-hackers |
Andres Freund <andres(at)2ndquadrant(dot)com> writes:
> On 2014-08-30 13:50:40 -0400, Tom Lane wrote:
>> A possible compromise is to sort a limited number of
>> buffers ---- say, collect a few thousand dirty buffers then sort, dump and
>> fsync them, repeat as needed.
> Yea, that's what I suggested nearby. But I don't really like it, because
> it robs us of the the chance to fsync() a relfilenode immediately after
> having synced all its buffers.
Uh, how so exactly? You could still do that. Yeah, you might fsync a rel
once per sort-group and not just once per checkpoint, but it's not clear
that that's a loss as long as the group size isn't tiny.
regards, tom lane
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