| From: | Sergey Koposov <koposov(at)ast(dot)cam(dot)ac(dot)uk> |
|---|---|
| To: | pgsql-hackers(at)postgresql(dot)org |
| Cc: | Robert Haas <robertmhaas(at)gmail(dot)com>, Merlin Moncure <mmoncure(at)gmail(dot)com>, Jeff Janes <jeff(dot)janes(at)gmail(dot)com>, Stephen Frost <sfrost(at)snowman(dot)net>, pgsql-hackers(at)postgresql(dot)org |
| Subject: | Re: 9.2beta1, parallel queries, ReleasePredicateLocks, CheckForSerializableConflictIn in the oprofile |
| Date: | 2012-05-27 18:45:19 |
| Message-ID: | alpine.LRH.2.02.1205271931420.20904@calx046.ast.cam.ac.uk |
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| Lists: | pgsql-hackers |
Hi,
I did another test using the same data and the same code, which I've
provided before and the performance of the single thread seems to be
degrading quadratically with the number of threads.
Here are the results:
Nthreads Time_to_execute_one_thread
1 8.1
2 7.8
3 8.1
4 9.0
5 10.2
6 11.4
7 13.3
8 16.1
9 19.0
10 21.4
11 23.8
12 27.3
13 30.2
14 32.0
15 34.1
16 37.5
Regards,
Sergey
On Sat, 26 May 2012, Stephen Frost wrote:
> * Sergey Koposov (koposov(at)ast(dot)cam(dot)ac(dot)uk) wrote:
>> Turning off synch seq scans doesn't help either. 18 sec
>> multithreaded run vs 7 sec single threaded.
>
> Alright, can you just time 'cat' when they're started a few seconds or
> whatever apart from each other? I can't imagine it being affected in
> the same way as these, but seems like it wouldn't hurt to check.
>
> Thanks,
>
> Stephen
>
*****************************************************
Sergey E. Koposov, PhD, Research Associate
Institute of Astronomy, University of Cambridge
Madingley road, CB3 0HA, Cambridge, UK
Tel: +44-1223-337-551 Web: http://www.ast.cam.ac.uk/~koposov/
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