Why is mysql opening so many files?

Question

linux

There is a database server on mysql. Some tables are large, so they are partitioned into 100 sub-tables. Faced the problem that mysql ran into the limits of open files. I increased the limits and started monitoring files opened by mysql with the lsof -u mysql | wc-l. Well, through grep I looked through the open files of specific tables. I also serve for the number of connections through the munin plugin. The statistics are such that with an average number of open connections of 12, I have 9500 open files of a specific (partitioned into 100 subtables) table. Those. the table has been opened at least 95 times, which is significantly more than the number of connections. munin showed a peak of 41 connections, which is also less. The number of open files is growing, and in steps (I observe through a self-written plugin for munin). What could be the reason? how to set up mysql so that he would not open the tables once again or close them? A quick Google did not give a result (maybe the request was not made up that way).

Answer 1

Comrade snevsky explains very intelligibly here habrahabr.ru/post/130999