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From:Jocelyn Fournier Date:March 9 2005 11:43pm
Subject:Re: Query_cache_size Question
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Even with only 16 Mo, your query cache is quite efficient (78% of your 
queries are fetched directly from the cache).
Try to increaze your query_cache_size until there's no more additional 
lowmem_prunes reported.
And executed from time to time FLUSH QUERY CACHE to defragment your 
query cache.

   Jocelyn

Mauricio Pellegrini a écrit :
> Thanks these are fresh results
> 
> | query_cache_limit            | 1048576  |
> | query_cache_min_res_unit     | 4096     |
> 
> 
> show  status like "ques%";
> +---------------+----------+
> | Variable_name | Value    |
> +---------------+----------+
> | Questions     | 14189604 |
> +---------------+----------+
> 
> 
> show  status like "qcache%";
> +-------------------------+----------+
> | Variable_name           | Value    |
> +-------------------------+----------+
> | Qcache_free_blocks      | 2731     |
> | Qcache_free_memory      | 12372064 |
> | Qcache_hits             | 11156553 |
> | Qcache_inserts          | 1945643  |
> | Qcache_lowmem_prunes    | 372898   |
> | Qcache_not_cached       | 509594   |
> | Qcache_queries_in_cache | 4101     |
> | Qcache_total_blocks     | 11000    |
> +-------------------------+----------+
> 
> 
> On Wed, 2005-03-09 at 20:19, Jocelyn Fournier wrote:
> 
>>Hi,
>>
>>How many questions for thoses results ?
>>There's a lot of lowmem_prunes, so I would indeed increase the memory 
>>size to reduce the risk of lowmem_prunes.
>>What is your query_cache_limit ?
>>
>>   Jocelyn
>>
>>Mauricio Pellegrini a écrit :
>>
>>>Thanks,  this the result of show status like "qcache%"
>>>
>>>+-------------------------+----------+
>>>| Variable_name           | Value    |
>>>+-------------------------+----------+
>>>| Qcache_free_blocks      | 3330     |
>>>| Qcache_free_memory      | 13372320 |
>>>| Qcache_hits             | 11119149 |
>>>| Qcache_inserts          | 1942009  |
>>>| Qcache_lowmem_prunes    | 372898   |
>>>| Qcache_not_cached       | 508528   |
>>>| Qcache_queries_in_cache | 3160     |
>>>| Qcache_total_blocks     | 9711     |
>>>+-------------------------+----------+
>>>
>>>Am I right at saying that the value (16Mb)is ok ?
>>>
>>>Qcache_not_cached means the number of query results that didn't get into
>>>the cache because of a space limitation ? 
>>>If so, perhaps adding few more Mb would improve that number , isn't it?
>>>
>>>
>>>
>>>
>>>On Wed, 2005-03-09 at 19:30, Dan Nelson wrote:
>>>
>>>
>>>>In the last episode (Mar 09), Mauricio Pellegrini said:
>>>>
>>>>
>>>>>Hi, I'm trying to tweak the execution time for querys on my mysql
>>>>>server which is using InnoDB.
>>>>>
>>>>>I know that there are a lot of things to check but one of them,
>>>>>perhaps not the most important, is the query_cache_size.
>>>>>
>>>>>I have a dual Xeon cpu with 4gb of ram and this is a Linux dedicated
>>>>>server which runs only Apache and Mysql 4.1.5
>>>>>
>>>>>I've declared Query_cache_size = 16M in the my.cnf file and I would
>>>>>say that in the whole we have 60% of select querys and a 40% of
>>>>>update querys.
>>>>>
>>>>>Is Query_cache_size=16M too conservative considering that I have 4Gb
>>>>>of ram ?
>>>>
>>>>A better question is: what is your current utilization of that 16MB
>>>>cache?  The query cache flushes any results dependant on a table when
>>>>that table is modified, so if you really have 40% updates, chances are
>>>>that very few queries are cachable at all.  Run
>>>>
>>>> show status like 'qcache%';
>>>>
>>>>, and take a look at free_memory, inserts, and hits.
>>>>
>>>>-- 
>>>>	Dan Nelson
>>>>	dnelson@stripped
>>>
>>>
>>>
> 
> 
Thread
Query_cache_size QuestionMauricio Pellegrini9 Mar
  • Re: Query_cache_size QuestionDan Nelson9 Mar
    • Re: Query_cache_size QuestionMauricio Pellegrini9 Mar
      • Re: Query_cache_size QuestionJocelyn Fournier10 Mar
        • Re: Query_cache_size QuestionMauricio Pellegrini10 Mar
          • Re: Query_cache_size QuestionJocelyn Fournier10 Mar
      • Re: Query_cache_size QuestionDan Nelson10 Mar
RE: Query_cache_size QuestionKostas Pyliouras9 Mar