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Date: Thu Jun 26 2008 - 10:39:09 CDT
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.
Senior Engineer, Koiaka GmbH
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"Ananda Kumar" <anandklgmail.com>
Re: Performance problem with more than 500 concurrent queries
mysqladmin -uroot -p debug
and check the error.log, see if there are any locks on the tables.
On 6/26/08, Guillermo.Acilukoiaka.com <Guillermo.Acilukoiaka.com> 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
> get all the children. Then it triggers new threads per children and it
> ends, leaving the other threads alive. Every thread does exactly the
> until they reach the leafs.
> When the threads reach the leafs, they read the description from the
> 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
> 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
> 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,
> the database is not doing anything with them. It sounds like the table
> locked, or something. I have checked the code several times but
> is correct. The code is only 25 lines long.
> The other symptom I can see is that when I start the script, there are
> 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
> change. I am Oracle DBA and I am trying to find some points in common
> 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?