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From:Rick James Date:August 29 2012 4:00pm
Subject:RE: qcache settings and block meaning
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> 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.

> -----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
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