How to set key_cache_size in Mysql

I saw our mysql server Key Efficiency hitrate reaching 100%, it's suggested by开发者_StackOverflow中文版 Mysql to increase key_cache_size setting. But how do I set this, and how do I check what the current setting is? Thanks,

David

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on linux/osx the settings are in /etc/my.cnf or /etc/mysql/my.cnf

this classic blog post has a nice overview of various settings: http://www.mysqlperformanceblog.com/2006/09/29/what-to-tune-in-mysql-server-after-installation/