High server load after upgrading to MySql5.5

Question

Around 10 hours ago we upgraded our server from 5.0. to 5.5 and currently the load on server is 150

When I do show process list I see a lot of queries with status

 Waiting for query cache lock 

And I get following output for SHOW STATUS LIKE 'Qcache%';

 +-------------------------+----------+ | Variable_name | Value | +-------------------------+----------+ | Qcache_free_blocks | 1 | | Qcache_free_memory | 33536864 | | Qcache_hits | 0 | | Qcache_inserts | 0 | | Qcache_lowmem_prunes | 0 | | Qcache_not_cached | 1463936 | | Qcache_queries_in_cache | 0 | | Qcache_total_blocks | 1 | +-------------------------+----------+ 8 rows in set (0.00 sec) 

Query cache param is set to

query_cache_size=32M

Our server is a single node with 8GB ram not sure why query cache is not working

Answer 1

I found the answer on serverfault it self, high load was because query cache was not working and query cache was not working because there was a hyphen in the database name.

When I renamed the database without hypen all went back to normal.

Reference to the ticket MySQL 5.5.9 Query Cache not working when schemas have hyphens ("-") in their name

Thanks Hussain