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From:Aaron Blew Date:June 26 2008 6:07pm
Subject:Re: Performance problem with more than 500 concurrent queries
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Generally your error log will be <HOSTNAME>.err in your data_dir.

-Aaron

On Thu, Jun 26, 2008 at 8:46 AM,  <Guillermo.Acilu@stripped> wrote:
> Sorry about the long signature in the email. I forgot to remove it...
>
> Guillermo
>
>
>
>
>
>
> From:
> Guillermo.Acilu@stripped
> To:
> mysql@stripped
> Date:
> 26.06.2008 17:39
> Subject:
> Re: Performance problem with more than 500 concurrent queries
>
>
>
> Hello,
>
> thanks for the answer.
>
> Where is the error.log stored? I run the mysqladmin, it requires the
> password and it exits immediately. But I cannot find any error.log.
>
> Thanks,
>
> Guillermo
>
>
> ---
> Guillermo Acilu
> Senior Engineer, Koiaka GmbH
>
> Koiaka GmbH
> Riesserkopfstr. 17
> 82467 Garmisch-Partenkirchen
> Tel: +49 (0)8821 9679555
> Fax: +49 (0)8821 730 9185
> Mailto:guillermo.acilu@stripped
> http://www.koiaka.com
>
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>
> From:
> "Ananda Kumar" <anandkl@stripped>
> To:
> "Guillermo.Acilu@stripped" <Guillermo.Acilu@stripped>
> Cc:
> mysql@stripped
> Date:
> 26.06.2008 16:30
> Subject:
> Re: Performance problem with more than 500 concurrent queries
>
>
>
> do this
>
> mysqladmin -uroot -p debug
>
> and check the error.log, see if there are any locks on the tables.
>
>
> On 6/26/08, Guillermo.Acilu@stripped <Guillermo.Acilu@stripped> wrote:
>>
>> Hello guys,
>>
>> I am new to this list and also kind of new to mysql too.
>>
>> I have a multi-thread application written in Ruby. The application is
>> reading one table that has two columns (Father, Children). As you might
>> suspect, this is a tree. The fields are foreign keys to a second table,
>> but the second table is not involved in the problem. The father-children
>> table has around 100000 rows.
>>
>> What the code does is simple. It starts in the root and it navigates the
>> tree up to the leafs. The first thread takes the root and runs a select
> to
>> get all the children. Then it triggers new threads per children and it
>> ends, leaving the other threads alive. Every thread does exactly the
> same
>> until they reach the leafs.
>>
>> When the threads reach the leafs, they read the description from the
> other
>> table using the leaf code, write the value in a global array and end.
>>
>> With a few rows, the algorithm is very fast. The problem starts when
> each
>> node has many children. To give you an idea, in one point in time there
>> are more than 600 threads running, but for some reason I always see no
>> more than two queries running in parallel from the MySQL Administrator.
>>
>> Each thread opens a new connection, runs the select, closes the
> connection
>> and ends. I have the default maximum connections, 100. So I should see
>> more queries in parallel than only two or three. All the connections are
>> constantly used while the algorithm runs. So the connections are open,
> but
>> the database is not doing anything with them. It sounds like the table
> is
>> locked, or something. I have checked the code several times but
> everything
>> is correct. The code is only 25 lines long.
>>
>> The other symptom I can see is that when I start the script, there are
> up
>> to 30 or 40 queries in parallel, but then the number goes down quickly
>> until it reaches only 2 or 3 concurrent queries a few seconds later. And
>> it stays like this.
>>
>> I've started playing around with the caches and memory values for MySQL
>> server, but to be honest, I am just guessing and the performance does
> not
>> change. I am Oracle DBA and I am trying to find some points in common
> with
>> mysql to gain performance, but I cannot find the source of the problem.
>>
>> I am with Mac OS X Leopard in a very fast machine and MySQL 5.0.51b. The
>> problem is also present in 5.1.25-rc
>>
>> Any ideas why is this happening?
>>
>> Thanks,
>>
>> Guillermo
>>
>
>
>
Thread
Performance problem with more than 500 concurrent queriesGuillermo.Acilu26 Jun
  • Re: Performance problem with more than 500 concurrent queriesAnanda Kumar26 Jun
    • Re: Performance problem with more than 500 concurrent queriesGuillermo.Acilu26 Jun
      • Re: Performance problem with more than 500 concurrent queriesGuillermo.Acilu26 Jun
        • Re: Performance problem with more than 500 concurrent queriesAaron Blew26 Jun
      • Re: Performance problem with more than 500 concurrent queriesmos26 Jun
        • Re: Performance problem with more than 500 concurrent queriesGuillermo.Acilu27 Jun
          • Re: Performance problem with more than 500 concurrent queriesjocelyn fournier27 Jun
            • Re: Performance problem with more than 500 concurrent queriesGuillermo.Acilu27 Jun