| From: | Bruce Momjian <bruce(at)momjian(dot)us> |
|---|---|
| To: | Robert Haas <robertmhaas(at)gmail(dot)com> |
| Cc: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>, Heikki Linnakangas <heikki(dot)linnakangas(at)enterprisedb(dot)com>, Itagaki Takahiro <itagaki(dot)takahiro(at)gmail(dot)com>, Greg Smith <greg(at)2ndquadrant(dot)com>, Ron Mayer <rm_pg(at)cheapcomplexdevices(dot)com>, Josh Berkus <josh(at)agliodbs(dot)com>, pgsql-hackers(at)postgresql(dot)org |
| Subject: | Re: Spread checkpoint sync |
| Date: | 2011-01-31 20:27:25 |
| Message-ID: | 201101312027.p0VKRP927189@momjian.us |
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| Lists: | pgsql-hackers |
Robert Haas wrote:
> Back to the idea at hand - I proposed something a bit along these
> lines upthread, but my idea was to proactively perform the fsyncs on
> the relations that had gone the longest without a write, rather than
> the ones with the most dirty data. I'm not sure which is better.
> Obviously, doing the ones that have "gone idle" gives the OS more time
> to write out the data, but OTOH it might not succeed in purging much
> dirty data. Doing the ones with the most dirty data will definitely
> reduce the size of the final checkpoint, but might also cause a
> latency spike if it's triggered immediately after heavy write activity
> on that file.
Crazy idea #2 --- it would be interesting if you issued an fsync
_before_ you wrote out data to a file that needed an fsync.
--
Bruce Momjian <bruce(at)momjian(dot)us> http://momjian.us
EnterpriseDB http://enterprisedb.com
+ It's impossible for everything to be true. +
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