… cache I would normally have on database server for those things which need to be cached — system files, binary log, FRM files, MySQL MyISAM system tables etc. Starting MySQL 5.5 MySQL uses asynchronous IO which should… untapped potential in MySQL IO as I think we should be getting very close numbers for buffered and unbuffered IO for read only…
Post: Query Profiling with MySQL: Bypassing caches
September 12, 2007 By 6 Comments
… 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… system in direct IO mode. Hardware Caches State of CPU cache may affect query execution speed but only lightly, the hardware IO cache may however cause dramatic difference. Hardware RAID cache…
Post: Profiling MySQL Memory Usage With Valgrind Massif
January 9, 2013 By 3 Comments
…_event::read_log_event(st_io_cache*, st_mysql_mutex*, Format_description_log_event const*) (in /usr/local/percona/mysql-5.5.28/usr…/percona/mysql-5.5.28/usr/sbin/mysqld) | | ->27.73% (114,084,096B) 0x728DAA: Log_event::read_log_event(st_io_cache*, st_mysql_mutex*, Format_description_log_event const*) (in /usr/local/percona/mysql-5.5.28/usr…
Post: Aligning IO on a hard disk RAID – the Benchmarks
June 9, 2011 By 13 Comments
… make sure caches were clean. OLTP benchmark As the goal was to compare performance with different IO alignment, not different MySQL configurations, I didn’t try out different MySQL versions or settings. Moreover, I…
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 … was OS or SAN cache hit rate – something you would not see otherwise. The bad luck is – MySQL currently does not provide… to look at the number of misses – number of IOs which MySQL needs to do. You better to look at global and…
Post: Ultimate MySQL variable and status reference list
January 8, 2011 By 4 Comments
…MySQL manual, especially… innodb_read_io_threadsblogpercona.commanual…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: MySQL caching methods and tips
April 4, 2011 By 5 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… the cache. Summary tables Queries that access a lot of data usually face two bottlenecks: disk IO and CPU usage. Disk IO is…
Post: Reasons for MySQL Replication Lag
July 29, 2011 By 9 Comments
… which switches RAID cache in write-through mode which can cause serve performance degradation. Configuration Changes Have you changed MySQL configuration ? OS… problem for similar reason as MySQL Restart – the traffic on different boxes might be different and hence cache content. Replication Traffic Changes… you should be able to see it by comparing IO MySQL is doing to IO going to devices from OS standpoint. If this…
Post: Virtualization and IO Modes = Extra Complexity
March 21, 2011 By 12 Comments
… system kernel, device driver and hardware to get behavior with caches and IO modes correctly. I remember us having a lot of troubles with fsync() not flushing hard drive write cache and so potential… RPM hard drives in RAID1. Because there is no write cache I expect it to do no more than a bit…
Post: Cache Performance Comparison
August 9, 2006 By 74 Comments
… continues cache experiements and has compared performance of MySQL Query Cache and File Cache. Jay uses Apache Benchmark to compare full full stack, cached or… 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… not fit in cache well – you will get disk IO which is very compared to performance of all in memory caches and so…
