| From: | Robert Haas <robertmhaas(at)gmail(dot)com> |
|---|---|
| To: | Simon Riggs <simon(at)2ndquadrant(dot)com> |
| Cc: | Greg Stark <stark(at)mit(dot)edu>, pgsql-hackers(at)postgresql(dot)org |
| Subject: | Re: patch: improve SLRU replacement algorithm |
| Date: | 2012-04-04 23:28:27 |
| Message-ID: | CA+TgmoaRf5ZJ8nqeWQ_J5mghz1sJJKvkUScfqu79sohvmSjF9w@mail.gmail.com |
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| Lists: | pgsql-hackers |
On Wed, Apr 4, 2012 at 4:34 PM, Simon Riggs <simon(at)2ndquadrant(dot)com> wrote:
> Interesting. You've spoken at length how this hardly ever happens and
> so this can't have any performance effect. That was the reason for
> kicking out my patch addressing clog history, wasn't it?
Uh, no, the reason for kicking out your clog history patch was that it
caused throughput to drop by a factor of 3 on a pgbench test at scale
factor 300. I assume you've got a bug there somewhere, or maybe
there's some other effect that hasn't been quantified.
> Why is this pgbench run accessing so much unhinted data that is > 1
> million transactions old? Do you believe those numbers? Looks weird.
Seems pretty normal to me, for the reasons Greg Stark states.
--
Robert Haas
EnterpriseDB: http://www.enterprisedb.com
The Enterprise PostgreSQL Company
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