… log flushing, which can cause downward spikes in performance. Other then that, I have also disabled query cache to avoid contention caused by query cache on write heavy workload. OK, so that was all about the configuration of the EC2 instance and MySQL. Now… mutexes, using “estimate” checkpoint method to reduce chances of log flush storms and disabling the query cache.
Post: Troubleshooting MySQL Memory Usage
March 21, 2012 By 3 Comments
… Check for Table Cache Related Allocations There are cases when MySQL will allocate a lot of memory for table cache, especially if you… down. What you might see instead is flushing tables regularly or reducing table cache reduces memory consumption to be withing the reason… Percona Server you can do better as you can query temporary tables too: mysql> select sum(data_length+index_length) from information…
Post: MySQL Query Cache
July 27, 2006 By 69 Comments
…FLUSH QUERY CACHE command can be used for query cache defragmentation but it may block query cache for rather long time for large query caches…
Post: Beware large Query_Cache sizes
March 23, 2007 By 3 Comments
… had number of consulting projects with MySQL Query Cache being source of serious problems. One would see queries both for MyISAM and Innodb tables… if your query cache size is in Gigabytes. At the same time check how many queries do you have in cache – Qcache_queries_in_cache – if… rather than constant insertion. You can also check how long FLUSH QUERY CACHE takes – if it is in seconds this is about as…
Post: Ultimate MySQL variable and status reference list
January 8, 2011 By 4 Comments
…query_alloc_block_sizeblogpercona.commanual query_cache_limitblogpercona.commanual query_cache_min_res_unitblogpercona.commanual query_cache_sizeblogpercona.commanual query_cache_typeblogpercona.commanual query_cache_wlock_invalidateblogpercona.commanual query…
Comment: What does Handler_read_rnd mean?
June 25, 2010 By 15 Comments
… row in set (0.00 sec) mysql> flush status; Query OK, 0 rows affected (0.00 sec) mysql> select * from t1; +——+ | n | +——+ | 1 | | 2… row in set (0.01 sec) mysql> flush query cache; Query OK, 0 rows affected (0.00 sec) mysql> show status like ‘Handler_read_rnd_next… second time you ran the query even if you flushed the query cache. However, if you did not flush the query cache, but flushed the tables, it did…
Post: What to tune in MySQL Server after installation
September 29, 2006 By 116 Comments
… Interview for people to work as MySQL DBAs or be involved with MySQL Performance in some way is… do not flush log to the disk but only flush it to OS cache. The log is still flushed to… operation. query_cache_size If your application is read intensive and you do not have application level caches this…
Post: MySQL Server Variables - SQL layer or Storage Engine specific.
June 8, 2006 By 14 Comments
…HEAP for in memory tables. So first MySQL versions did not bother naming variables with… slow query log or general log. flush, flush_time Flushing (closing) of tables after query is complete or every flush_… and Innodb. Some SQL level items as Query Cache also could use this feature. low_priority…
Comment: Beware large Query_Cache sizes
March 25, 2007 By 3 Comments
… to insert the freed query cache record into the sorted list of free blocks. Flush query cache defragments the query cache, so regular flushing is one possible way of reducing the impact. On a related topic, http://bugs.mysql.com…
Post: Query Profiling with MySQL: Bypassing caches
September 12, 2007 By 6 Comments
… is simple – because SQL_NO_CACHE only bypasses query cache but it has no change on other caches, which are MySQL Caches – Innodb Buffer Pool and… these caches? For MySQL Caches you can restart MySQL and this is the only way to clean all of the caches. You can do FLUSH TABLES to clean MySQL…
