Core: reusing connections in advance. Reworked connections reuse, so closing connections is attempted in advance, as long as number of free connections is less than 1/16 of worker connections configured. This ensures that new connections can be handled even if closing a reusable connection requires some time, for example, for a lingering close (ticket #2017). The 1/16 ratio is selected to be smaller than 1/8 used for disabling accept when working with accept mutex, so nginx will try to balance new connections to different workers first, and will start reusing connections only if this won't help.