…What cache hit rate is good for optimal MySQL Performance” is typical question I’m asked. It could by … good was OS or SAN cache hit rate – something you would not see otherwise. The bad luck is – MySQL currently does not provide this…”, “OS file writes” from SHOW INNODB STATUS for Innodb tables. In MySQL 5.0+ you can also use Innodb_data_reads, and…
Post: Why you should ignore MySQL's key cache hit ratio
February 28, 2010 By 27 Comments
… 99% of advice about tuning MySQL‘s key cache hit ratio is wrong, even when…cache interchangeably. However, I will be careful about the difference between “rate” and “ratio”. In this article, the key cache miss rate… machine that’s dedicated to MyISAM tables. Consider your mixture of storage engines (…
Post: MySQL Query Cache
July 27, 2006 By 69 Comments
… from this table are invalidated at once. Most of them quite likely would not have change their result set but MySQL has… queries as if query cache hit happens Com_select is not incremented. But if you have just 20% Cache hit rate does it mean it is not worth it ? Not really it depends on which queries are cached, as well…
Post: Beware large Query_Cache sizes
March 23, 2007 By 3 Comments
… consulting projects with MySQL Query Cache being source of serious problems. One would see queries both for MyISAM and Innodb tables mysteriously stalling… to happen more regularly but this also should affect query cache hit rate.
Post: MySQL caching methods and tips
April 4, 2011 By 4 Comments
… same time. These cache stampedes are essentially the cause of the unpredictable performance of the MySQL query cache, since the rate of invalidation can not be controlled, and multiple cache entries may be invalidated by a single table change… run when the cache is empty. When talking about cache, the miss path is at least as important as the hit one. In…
Comment: When should you store serialized objects in the database?
January 21, 2010 By 42 Comments
… isn’t worth it if you have a lot of tables that you’re often modifying. Sure, this is purportedly fixed… will read and write through to cache without any extra effort. We see a 99.9% cache hit rate in production. In practice, that means that even if the queries through to MySQL are somewhat slower, the…
Post: Using flow control functions for performance monitoring queries
May 24, 2008 By 12 Comments
… As you can see in this table we have recorded “wtime” which is… they often have different performance profile. mysql> select count(*) cnt, avg(wtime) avw,…cache (or be served from the cache all together). Bots however tend to visit distinct pages which tends to have significantly lower cache hit rate…
Comment: Shard-Query turbo charges Infobright community edition (ICE)
May 6, 2011 By 22 Comments
… would have compared. 3. Which indexes were present on the table, because the queries look like natural ones for very effective…. Why virtual servers were used instead of multiple instances of MySQL on one, which generally has lower overhead. 5. What the… shorter rows to improve cache hit rates. I tend to grimace when I see 100 character varchars in frequently queried tables without covering indexes…
Post: SHOW INNODB STATUS walk through
July 17, 2006 By 40 Comments
…mysql tables in use 1, locked 0 is number of tables used by transaction in question (meaning it was accessed) and number of tables…done to OS cache, and being …hit ratio which measures buffer pool efficiency. 1000/1000 corresponds to 100% hit rate. It is hard to tell what buffer pool hit rate…
Comment: MySQL Query Cache
June 3, 2009 By 69 Comments
… even if you cache whole pages/parts that way you should combine it with mysql-qery-cache because if your manual cache is outdated…: 1B) [OK] Key buffer hit rate: 99.7% (14M cached / 44K reads) [OK] Query cache efficiency: 87.9% (5M cached / 6M selects) On this machine… the pages are stored in a mysql-caching table because its stoopid to use memcached/shm for caching on a shared-hosting. So you…
