… that somewhere around of 99% of advice about tuning MySQL‘s key cache hit ratio is wrong, even when you hear it… the difference between “rate” and “ratio”. In this article, the key cache miss rate is defined as the number of misses per unit of time, with the units of operations per second. The key cache miss…
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 … good was OS or SAN cache hit rate – something you would not see otherwise. The bad luck is – MySQL currently does not provide… would be to look at the number of misses – number of IOs which MySQL needs to do. You better to look at…
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… ones you have to run when the cache is empty. When talking about cache, the miss path is at least as important as…
Post: Beyond great cache hit ratio
May 19, 2010 By 2 Comments
… are 10 more requests which resulted in misses and caused MySQL queries. The hit ratio is 90%. Imagine …have 1 request (hit) now and 10 misses which drops your hit rate down to less than 10% but … cache miss. Maximize amount of uses of the cache item It is the most efficient if the item in the cache…
Post: table_cache negative scalability
November 16, 2009 By 23 Comments
…. So if you tune table cache is “normal” case and is able to bring down your miss rate (opened_tables) to 10/sec or less by using large table_cache you should do so… in MySQL 5.1, lets see how MySQL 5.4 behaves. MySQL 5.4.2 MySQL 5.4.2 has higher default table_open_cache…
Comment: Choosing innodb_buffer_pool_size
November 25, 2010 By 38 Comments
Hello, My Mysql server is heavily loaded, now 300 qps average. It uses %… Key cache miss rate is 1 : 63 Key buffer free ratio = 74 % Your key_buffer_size seems to be fine QUERY CACHE Query cache is enabled Current query_cache_size = 256 M Current query_cache_used = 19 M Current query_cache_limit = 1 M Current Query cache…
Post: Heikki Tuuri Innodb answers - Part I
October 26, 2007 By 17 Comments
…. They also allow to reduce number of TLB cache misses. huge pages along however do not stop IO…. Any plans to enable tuning of the checkpointing rate? Postgres exposes this data and allows the user…? HT: ha_innodb.cc in 5.1: static MYSQL_SYSVAR_ULONG(thread_concurrency, srv_thread_concurrency, PLUGIN…
Comment: Shard-Query turbo charges Infobright community edition (ICE)
May 6, 2011 By 22 Comments
… servers were used instead of multiple instances of MySQL on one, which generally has lower overhead. 5…the data further into shorter rows to improve cache hit rates. I tend to grimace when I …easy normalisation. To some extent these questions are missing the point about generic star schema queries …
Post: Updated msl (microslow) patch, installation walk-through!
April 20, 2008 By 17 Comments
…mysql-5.0.51a/ mysql-5.0.51a/bdb/ mysql-5.0.51a/bdb/Makefile.in mysql-5.0.51a/bdb/btree/ mysql….cc patching file sql/sql_cache.cc patching file sql/sql_… in a comma-separated string. [qc_miss, full_scan, full_join, tmp_table…and SET GLOBAL. log_slow_rate_limit=# Rate limit statement writes to slow …
Post: Heikki Tuuri answers to Innodb questions, Part II
November 4, 2007 By 13 Comments
…cache and when sequentially written to the drives at the rate of 100MB/sec or more. This cache…_buffer_pool_size Q36: There have been several MySQL bugs opened about multi-core scalability (concurrent queries,… at a time, that are esentially reads misses (10ms each). The reads are not excactly …
