| From: | Mark Kirkwood <mark(dot)kirkwood(at)catalyst(dot)net(dot)nz> |
|---|---|
| To: | Heikki Linnakangas <hlinnakangas(at)vmware(dot)com>, Claudio Freire <klaussfreire(at)gmail(dot)com> |
| Cc: | Jim Nasby <jim(at)nasby(dot)net>, Greg Stark <stark(at)mit(dot)edu>, Josh Berkus <josh(at)agliodbs(dot)com>, Robert Haas <robertmhaas(at)gmail(dot)com>, PostgreSQL-development <pgsql-hackers(at)postgresql(dot)org> |
| Subject: | Re: ANALYZE sampling is too good |
| Date: | 2013-12-10 00:20:47 |
| Message-ID: | 52A65E5F.7050509@catalyst.net.nz |
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| Thread: | |
| Lists: | pgsql-hackers |
On 10/12/13 13:14, Mark Kirkwood wrote:
> On 10/12/13 12:14, Heikki Linnakangas wrote:
>>
>>
>> I took a stab at using posix_fadvise() in ANALYZE. It turned out to
>> be very easy, patch attached. Your mileage may vary, but I'm seeing a
>> nice gain from this on my laptop. Taking a 30000 page sample of a
>> table with 717717 pages (ie. slightly larger than RAM), ANALYZE takes
>> about 6 seconds without the patch, and less than a second with the
>> patch, with effective_io_concurrency=10. If anyone with a good test
>> data set loaded would like to test this and post some numbers, that
>> would be great.
>>
>>
>
>
>
> I did a test run:
>
> pgbench scale 2000 (pgbench_accounts approx 25GB).
> postgres 9.4
>
> i7 3.5Ghz Cpu
> 16GB Ram
> 500 GB Velociraptor 10K
>
> (cold os and pg cache both runs)
> Without patch: ANALYZE pgbench_accounts 90s
> With patch: ANALYZE pgbench_accounts 91s
>
> So I'm essentially seeing no difference :-(
Arrg - sorry forgot the important bits:
Ubuntu 13.10 (kernel 3.11.0-14)
filesystem is ext4
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