… that somewhere around of 99% of advice about tuning MySQL‘s key cache hit ratio is wrong, even when you hear it from… scientific and authoritative — the “key cache hit ratio.” This is a shame. When you are new to MySQL, trying to configure my.cnf… trust the cache‘s creator and assume that misses are more expensive than hits, then you care about cache misses, not cache hits. A Key…
Post: What MySQL buffer cache hit rate should you target
June 29, 2006 By 5 Comments
…What cache hit rate is good for optimal MySQL Performance” is typical question I’m asked. It could by … be understand is – cache hit ratio can be computed differently for different engines. For example for Innodb page hits are counted for all… good was OS or SAN cache hit rate – something you would not see otherwise. The bad luck is – MySQL currently does not provide…
Post: Ultimate MySQL variable and status reference list
January 8, 2011 By 4 Comments
… the amazing MySQL manual, especially the option and variable …cache_hitsblogpercona.commanual Ssl_session_cache_missesblogpercona.commanual Ssl_session_cache_modeblogpercona.commanual Ssl_session_cache_overflowsblogpercona.commanual Ssl_session_cache_sizeblogpercona.commanual Ssl_session_cache…
Post: Why don't our new Nagios plugins use caching?
February 19, 2012 By 1 Comment
… went further than that; I didn’t cache the data retrieved from MySQL, I cached the resulting metrics. This avoids having to do… there might have been a misunderstanding — perhaps caching was understood to reduce load on MySQL, rather than reducing load on the Cacti… inside of MySQL. If you take the typical mass-market monitoring program’s silly “alert on 99 different kinds of cache hit ratio…
Post: MySQL Query Cache
July 27, 2006 By 69 Comments
…, thinking MySQL Query Cache is the same as Oracle Query Cache – meaning cache where execution plans are cached. MySQL Query Cache is not. It does not cache the… normalized (would require parsing) before cache lookup, so they have to match byte by byte for cache hit to happen. This means if… queries as if query cache hit happens Com_select is not incremented. But if you have just 20% Cache hit rate does it mean…
Post: Beyond great cache hit ratio
May 19, 2010 By 2 Comments
… 10 more requests which resulted in misses and caused MySQL queries. The hit ratio is 90%. Imagine now you have found a… multiple pages and multiple users this will maximize cache efficiency while reduce amount of cache space required. The importance of this advice… get best hit rate. Others which have hundreds of page views per user per session may be good enough with caches which…
Post: Should we give a MySQL Query Cache a second chance ?
April 10, 2011 By 63 Comments
… invalidation is enough. Improve Manageability What is in the MySQL Query Cache ? How many hits did we get for this query item ? Right… Refresh MySQL Query Cache causes not uniform performance as you get very fast responses for hits but you might need to take significant hit for misses. This is especially the problem for very expensive queries. The good thing about MySQL Query Cache is it…
Post: The new cool MySQL patch has landed! Check your queries performance!
October 31, 2007 By 16 Comments
…: 56 Rows_examined: 1113 LOGGING OF THE REPLICATED STATEMENTS Normally MySQL will not write into slow log any queries executed by…: Yes Disk_filesort: No Merge_passes: 0 QC_Hit tells whether query cache hit occurred or not. If it says ‘Yes’, then…. INNODB USAGE The final part are the InnoDB usage statistics. MySQL currently allows you to see many per-session statistics for…
Post: Cache Performance Comparison
August 9, 2006 By 73 Comments
… queries to MySQL parsing may be performance bottleneck, assuming PHP opcode cache is not used. Also different applications may have different cache hit ratios… are: Cache Type Cache Gets/sec Array Cache 365000 APC Cache 98000 File Cache 27000 Memcached Cache (TCP/IP) 12200 MySQL Query Cache (TCP/IP) 9900 MySQL Query Cache (Unix… file cache to work you need file named “test” containing “MyTestString” 2) You need to create table test.test for MySQL Cache to…
Post: MySQL caching methods and tips
April 4, 2011 By 4 Comments
… some of the most common cache methods for MySQL. Popular cache methods The MySQL query cache When the query cache is enabled, MySQL examines each query to see if the contents have been stored in the query cache… run when the cache is empty. When talking about cache, the miss path is at least as important as the hit one. In…
