| From: | Michael Paquier <michael(at)paquier(dot)xyz> |
|---|---|
| To: | Andrew Dunstan <andrew(dot)dunstan(at)2ndquadrant(dot)com> |
| Cc: | Robert Haas <robertmhaas(at)gmail(dot)com>, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>, Pavan Deolasee <pavan(dot)deolasee(at)gmail(dot)com>, Simon Riggs <simon(at)2ndquadrant(dot)com>, Peter Eisentraut <peter(dot)eisentraut(at)2ndquadrant(dot)com>, Michael Paquier <michael(dot)paquier(at)gmail(dot)com>, PostgreSQL-development <pgsql-hackers(at)postgresql(dot)org> |
| Subject: | Re: Changing WAL Header to reduce contention during ReserveXLogInsertLocation() |
| Date: | 2018-03-28 06:48:56 |
| Message-ID: | 20180328064856.GL1105@paquier.xyz |
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| Lists: | pgsql-hackers |
On Wed, Mar 28, 2018 at 02:13:19PM +1030, Andrew Dunstan wrote:
> On Wed, Mar 28, 2018 at 12:57 PM, Michael Paquier <michael(at)paquier(dot)xyz> wrote:
>> Something that would address the issue would be to enforce a segment
>> switch after each checkpoint, but that's a high price to pay on mostly
>> idle systems with large WAL segments, which is not appealing either, and
>> this even if the checkpoint skip logic has been fixed in v10 with the
>> concept of "important" WAL records.
>
> If the system is mostly idle would it really matter that much?
We cannot assume that all archive commands support compression, even if
the rest of a forcibly switched segment is filled with zeros, so that
would cause extra I/O effort for such instances. I see quite a lot of
downsides to that.
--
Michael
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