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Message-ID: <4DCB8C31.2000606@gmail.com>
Date: Thu, 12 May 2011 10:28:49 +0300
From: Vitalii Tymchyshyn <tivv00@gmail.com>
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To: Aren Cambre <aren@arencambre.com>
CC: Craig Ringer <craig@postnewspapers.com.au>,
	pgsql-performance@postgresql.org
Subject: Re: Postgres refusing to use >1 core
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	<BANLkTi=NC8UY4Se-Z_iJMVPWPMKyzc5fog@mail.gmail.com>
In-Reply-To: <BANLkTi=NC8UY4Se-Z_iJMVPWPMKyzc5fog@mail.gmail.com>
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12.05.11 06:18, Aren Cambre ???????(??):
>
>     > Using one thread, the app can do about 111 rows per second, and it's
>     > only exercising 1.5 of 8 CPU cores while doing this. 12,000,000
>     rows /
>     > 111 rows per second ~= 30 hours.
>
>     I don't know how I missed that. You ARE maxing out one cpu core, so
>     you're quite right that you need more threads unless you can make your
>     single worker more efficient.
>
>
> And the problem is my app already has between 20 and 30 threads. 
> Something about C#'s PLINQ may not be working as intended...
>
Have you checked that you are really doing fetch and processing in 
parallel? Dunno about C#, but under Java you have to make specific 
settings (e.g. setFetchSize) or driver will fetch all the data on query 
run. Check time needed to fetch first row from the query.

Best regards, Vitalii Tymchyshyn

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    12.05.11 06:18, Aren Cambre &#1085;&#1072;&#1087;&#1080;&#1089;&#1072;&#1074;(&#1083;&#1072;):
    <blockquote
      cite="mid:BANLkTi=NC8UY4Se-Z_iJMVPWPMKyzc5fog@mail.gmail.com"
      type="cite">
      <div class="gmail_quote">
        <blockquote class="gmail_quote" style="margin: 0pt 0pt 0pt
          0.8ex; border-left: 1px solid rgb(204, 204, 204);
          padding-left: 1ex;">
          <div class="im">&gt; Using one thread, the app can do about
            111 rows per second, and it's<br>
            &gt; only exercising 1.5 of 8 CPU cores while doing this.
            12,000,000 rows /<br>
            &gt; 111 rows per second ~= 30 hours.<br>
            <br>
          </div>
          I don't know how I missed that. You ARE maxing out one cpu
          core, so<br>
          you're quite right that you need more threads unless you can
          make your<br>
          single worker more efficient.<br>
        </blockquote>
        <div><br>
        </div>
        <div>And the problem is my app already has between 20 and 30
          threads. Something about C#'s&nbsp;PLINQ may not be working as
          intended...</div>
        <br>
      </div>
    </blockquote>
    Have you checked that you are really doing fetch and processing in
    parallel? Dunno about C#, but under Java you have to make specific
    settings (e.g. setFetchSize) or driver will fetch all the data on
    query run. Check time needed to fetch first row from the query.<br>
    <br>
    Best regards, Vitalii Tymchyshyn<br>
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