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From:Todd Lyons Date:August 18 2010 2:58pm
Subject:Re: Moving from one MySQL server to three MySQL servers?
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On Thu, Aug 5, 2010 at 8:35 AM, Nunzio Daveri <nunziodaveri@stripped> wrote:
>
> The server in this case is a stand alone with nothing more then CentOS and MySQL
> 5.1.44 on it.  The drives are sas 10K rpm drives.  The problem I see is
> that
> when you stress test the server (typically by running loads of reports -
> selects, joins) the machine hits 98% cpu and leaves only 800mb of free RAM out
> of the 16 GB of which I told it to allocate 12GB for Innodb in my.cnf.  Once
> the
> server sucks up all the memory when we are stress testing it, it holds the 12 gb
> as hostage and refuses to release it back into the pool, regardless of weather

We had a similar system where the innodb data dictionary (poor-man's
description is an in-memory map of all the tables it has opened up to
that point) consumed all free memory and the kernel started killing
processes to get some back.  At the time, stock mysql did not have the
ability to limit the size of the data dictionary memory usage (and I
don't see it as an available option for 5.1.x currently), so I tested
XtraDB and it prevented the memory usage from growing without bound.
XtraDB also gave us lots of knobs to twiddle and extra insights into
what innodb was doing.  I've not experimented with current mysql 5.1.x
to see how much of that extra control has made it into the mainline.

> only 800mb of ram free???  If I start to stress it again then it starts to go
> into swap.  Really weird, thus wanting to split the load onto 3 machines.

When you restarted the stress test, did it access new tables or the
same ones that the previous stress test did?  What happens if you tell
innodb to use less memory and do your tests?  Have you found any way
to make mysql not run out of memory?

-- 
Regards...      Todd
I seek the truth...it is only persistence in self-delusion and
ignorance that does harm.  -- Marcus Aurealius
Thread
Moving from one MySQL server to three MySQL servers?Nunzio Daveri4 Aug
  • Re: Moving from one MySQL server to three MySQL servers?Warren Young4 Aug
  • Re: Moving from one MySQL server to three MySQL servers?Wm Mussatto4 Aug
    • Re: Moving from one MySQL server to three MySQL servers?Prabhat Kumar4 Aug
      • Re: Moving from one MySQL server to three MySQL servers?Andrés Tello5 Aug
  • Re: Moving from one MySQL server to three MySQL servers?Joerg Bruehe5 Aug
  • RE: Moving from one MySQL server to three MySQL servers?Steven Staples5 Aug
    • Re: Moving from one MySQL server to three MySQL servers?Nunzio Daveri5 Aug
      • Re: Moving from one MySQL server to three MySQL servers?Andrés Tello6 Aug
      • Re: Moving from one MySQL server to three MySQL servers?Warren Young9 Aug
      • Re: Moving from one MySQL server to three MySQL servers?Todd Lyons18 Aug