| From: | Peter Geoghegan <peter(at)2ndquadrant(dot)com> |
|---|---|
| To: | Jeff Janes <jeff(dot)janes(at)gmail(dot)com> |
| Cc: | pgsql-hackers <pgsql-hackers(at)postgresql(dot)org> |
| Subject: | Re: tuplesort memory usage: grow_memtuples |
| Date: | 2012-07-25 21:51:50 |
| Message-ID: | CAEYLb_VuaHP3hNMJkB6fERPwQSsfyeKQ3YO35id0kc3n1N==dg@mail.gmail.com |
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| Lists: | pgsql-hackers |
On 3 March 2012 20:22, Jeff Janes <jeff(dot)janes(at)gmail(dot)com> wrote:
> Add it all up, and instead of pre-reading 32 consecutive 8K blocks, it
> pre-reads only about 1 or 2 consecutive ones on the final merge. Now
> some of those could be salvaged by the kernel keeping track of
> multiple interleaved read ahead opportunities, but in my hands vmstat
> shows a lot of IO wait and shows reads that seem to be closer to
> random IO than large read-ahead. If it used truly efficient read
> ahead, CPU would probably be limiting.
Can you suggest a benchmark that will usefully exercise this patch?
--
Peter Geoghegan http://www.2ndQuadrant.com/
PostgreSQL Development, 24x7 Support, Training and Services
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