Enables timing of database I/O calls. This parameter is off by default, because it will repeatedly query the operating system for the current time, which may cause significant overhead on some platforms. You can use the pgtesttiming tool to measure the overhead of timing on your system. I/O timing information is displayed in pg-stat-database-view, in the output of sql-explain when the
BUFFERS option is used, and by pgstatstatements. Only superusers can change this setting.