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Query cache was never filled up
Posted by: Reynard H ()
Date: August 28, 2010 09:58AM

Hi,

I have setup query_cache with this settings

mysql> show variables like '%query_cache%';
+------------------------------+-----------+
| Variable_name | Value |
+------------------------------+-----------+
| have_query_cache | YES |
| query_cache_limit | 4194304 |
| query_cache_min_res_unit | 4096 |
| query_cache_size | 268435456 |
| query_cache_type | ON |
| query_cache_wlock_invalidate | OFF |
+------------------------------+-----------+

mysql> SHOW STATUS LIKE 'Qcache%';
+-------------------------+-----------+
| Variable_name | Value |
+-------------------------+-----------+
| Qcache_free_blocks | 8540 |
| Qcache_free_memory | 217974872 |
| Qcache_hits | 45906852 |
| Qcache_inserts | 31292381 |
| Qcache_lowmem_prunes | 3389670 |
| Qcache_not_cached | 4702447 |
| Qcache_queries_in_cache | 28918 |
| Qcache_total_blocks | 66504 |
+-------------------------+-----------+

So mysql never seem to fill the entire cache size (in this case < 20%), as shown by the high number of Qcache_free_memory. this is the case everytime I check the status. (so it's not because it hasn't warm up). and another problematic thing is that Qcache_lowmem_prunes is really high, which means that it prunes the cache because of low memory but there are so much unused memory.

I'm using mysql 5.0.91 on RHEL5. Any idea what's going on here?
any hints would be greatly appreciated and thanks for reading :)

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Subject Views Written By Posted
Query cache was never filled up 2930 Reynard H 08/28/2010 09:58AM
Re: Query cache was never filled up 1228 Rick James 08/29/2010 09:25PM


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