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 02:04:34 |
Message-ID: | 52A676B2.9040000@catalyst.net.nz |
Views: | Raw Message | Whole Thread | Download mbox | Resend email |
Thread: | |
Lists: | pgsql-hackers |
On 10/12/13 13:53, Mark Kirkwood wrote:
> On 10/12/13 13:20, Mark Kirkwood wrote:
>> 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
>>
>>
>>
>
> Doing the same test as above, but on a 80GB Intel 520 (ext4 filesystem
> mounted with discard):
>
> (cold os and pg cache both runs)
> Without patch: ANALYZE pgbench_accounts 5s
> With patch: ANALYZE pgbench_accounts 5s
>
>
>
>
>
Redoing the filesystem on the 520 as btrfs didn't seem to make any
difference either:
(cold os and pg cache both runs)
Without patch: ANALYZE pgbench_accounts 6.4s
With patch: ANALYZE pgbench_accounts 6.4s
From | Date | Subject | |
---|---|---|---|
Next Message | Mark Kirkwood | 2013-12-10 02:11:13 | Re: ANALYZE sampling is too good |
Previous Message | Jim Nasby | 2013-12-10 01:11:49 | Re: dblink performance regression |