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From:Raphael Bauduin Date:August 30 2012 7:06am
Subject:Re: qcache settings and block meaning
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On Wed, Aug 29, 2012 at 6:00 PM, Rick James <rjames@stripped> wrote:
>> It hasn't been purged resultly ('recently'?) AFAIK.
> Purging happens automatically -- Whenever ANY change is made to a table, ALL entries
> in the QC for that table are purged.

Ok, then it has been purged recently. I'll try disabling the query
cache and report back.


>
>> -----Original Message-----
>> From: raphinou@stripped [mailto:raphinou@stripped] On Behalf Of
>> Raphael Bauduin
>> Sent: Wednesday, August 29, 2012 2:16 AM
>> To: Rick James
>> Cc: mysql@stripped
>> Subject: Re: qcache settings and block meaning
>>
>> On Tue, Aug 28, 2012 at 6:40 PM, Rick James <rjames@stripped>
>> wrote:
>> >> | Qcache_hits                       | 56418967     |
>> >> | Qcache_inserts                    | 48601636     |
>> > That's a low hit rate.  Perhaps you should simply turn off the Query
>> cache?
>> >
>> >> | Qcache_free_memory                | 46945512     |
>> > That's a big fraction of the total.  Either the QC is unnecessarily
>> big, or it was recently purged.
>>
>> It hasn't been purged resultly AFAIK.
>>
>> >
>> >> | Qcache_lowmem_prunes              | 21948806     |
>> > What is Uptime?  This may be a lot of prunes per second.
>>
>> Uptime is 65days, resulting in a little less than 4 per second.
>> >
>> > Purging stuff out of 128MB _may_ slow your system down more than the
>> benefit you are getting.
>> > I recommend turning off the QC for systems with constant write
>> activity.
>> > Otherwise, 50M is a reasonable max.
>>
>> Thanks for your feedback. These question were going to be the topic of
>> my next mail to the list, but you anticipated correctly :-)
>>
>> Raph
>>
>> >
>> >> -----Original Message-----
>> >> From: raphinou@stripped [mailto:raphinou@stripped] On Behalf Of
>> >> Raphael Bauduin
>> >> Sent: Tuesday, August 28, 2012 7:12 AM
>> >> To: mysql@stripped
>> >> Subject: qcache settings and block meaning
>> >>
>> >> Hi,
>> >>
>> >> I have a mysql server running with the query cache size being 128M
>> >> (134217728 bytes).
>> >>
>> >> Here are the qcache variables values:
>> >>
>> >> | Qcache_free_blocks                | 13758        |
>> >> | Qcache_free_memory                | 46945512     |
>> >> | Qcache_hits                       | 56418967     |
>> >> | Qcache_inserts                    | 48601636     |
>> >> | Qcache_lowmem_prunes              | 21948806     |
>> >> | Qcache_not_cached                 | 39066097     |
>> >> | Qcache_queries_in_cache           | 44858        |
>> >> | Qcache_total_blocks               | 104668
>> >>
>> >> And the query_cache_min_res_unit is 4096 .
>> >>
>> >> I'm not sure what the meaning of a block is. For the query cache
>> size
>> >> and the number of total blocks, I have a block size of
>> >> 134217728/104668 = 1282.3186 , which is a strange number for a block
>> >> size. Am I wrong somewhere?
>> >>
>> >> Thanks
>> >>
>> >> Raph
>> >>
>> >> --
>> >> MySQL General Mailing List
>> >> For list archives: http://lists.mysql.com/mysql
>> >> To unsubscribe:    http://lists.mysql.com/mysql
>> >
>>
>>
>>
>> --
>> Web database: http://www.myowndb.com
>> Free Software Developers Meeting: http://www.fosdem.org



-- 
Web database: http://www.myowndb.com
Free Software Developers Meeting: http://www.fosdem.org
Thread
qcache settings and block meaningRaphael Bauduin28 Aug
  • Re: qcache settings and block meaningJohan De Meersman28 Aug
  • RE: qcache settings and block meaningRick James28 Aug
    • Re: qcache settings and block meaningRaphael Bauduin29 Aug
      • RE: qcache settings and block meaningRick James29 Aug
        • Re: qcache settings and block meaningRaphael Bauduin30 Aug