On Wed, Aug 29, 2012 at 6:00 PM, Rick James <rja...@yahoo-inc.com> 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: raphi...@gmail.com [mailto:raphi...@gmail.com] On Behalf Of
>> Raphael Bauduin
>> Sent: Wednesday, August 29, 2012 2:16 AM
>> To: Rick James
>> Cc: mysql@lists.mysql.com
>> Subject: Re: qcache settings and block meaning
>>
>> On Tue, Aug 28, 2012 at 6:40 PM, Rick James <rja...@yahoo-inc.com>
>> 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: raphi...@gmail.com [mailto:raphi...@gmail.com] On Behalf Of
>> >> Raphael Bauduin
>> >> Sent: Tuesday, August 28, 2012 7:12 AM
>> >> To: mysql@lists.mysql.com
>> >> 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
>> >>
>> >> --
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>> >
>>
>>
>>
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