| From: | Jim Nasby <Jim(dot)Nasby(at)BlueTreble(dot)com> |
|---|---|
| To: | Peter Eisentraut <peter_e(at)gmx(dot)net>, Bruce Momjian <bruce(at)momjian(dot)us>, Alvaro Herrera <alvherre(at)2ndquadrant(dot)com> |
| Cc: | Simon Riggs <simon(dot)riggs(at)2ndquadrant(dot)com>, Andres Freund <andres(at)anarazel(dot)de>, Pavan Deolasee <pavan(dot)deolasee(at)gmail(dot)com>, Greg Stark <stark(at)mit(dot)edu>, Simon Riggs <simon(at)2ndquadrant(dot)com>, PostgreSQL-development <pgsql-hackers(at)postgresql(dot)org>, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>, Michael Paquier <michael(dot)paquier(at)gmail(dot)com>, Jeff Janes <jeff(dot)janes(at)gmail(dot)com>, Amit Kapila <amit(dot)kapila16(at)gmail(dot)com>, Robert Haas <robertmhaas(at)gmail(dot)com> |
| Subject: | Re: Turning off HOT/Cleanup sometimes |
| Date: | 2015-04-22 15:37:38 |
| Message-ID: | 5537C042.6080006@BlueTreble.com |
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| Lists: | pgsql-hackers |
On 4/21/15 4:07 PM, Peter Eisentraut wrote:
> On 4/21/15 4:45 PM, Jim Nasby wrote:
> In order for a background worker to keep up with some of the workloads
> that have been presented as counterexamples, you'd need multiple
> background workers operating in parallel and preferring to work on
> certain parts of a table. That would require a lot more sophisticated
> job management than we currently have for, say, autovacuum.
My thought was that the foreground queries would send page IDs to the
bgworker via a shmq. If the queries have to do much waiting at all on IO
then I'd expect the bgworker to be able to keep pace with a bunch of
them since it's just grabbing buffers that are already in the pool (and
only those in the pool; it wouldn't make sense for it to pull it back
from the kernel, let alone disk).
We'd need to code this so that if a queue fills up the query doesn't
block; we just skip that opportunity to prune. I think that'd be fine.
--
Jim Nasby, Data Architect, Blue Treble Consulting
Data in Trouble? Get it in Treble! http://BlueTreble.com
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