The process count keeps growing! — Cyrus IMAP 3.2.3 documentation

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# The process count keeps growing!

If you notice that your imapd process count continues to grow and never decreases, there are a number of options which may be affecting it.

## 1. Reuse count

By default, imapd processes will remain alive for 250 new connections before shutting down. Setting this to a lower value will reduce the amount of time unused processes hang around. There is a tradeoff between startup/shutdown overhead and process longevity.

The use setting is the - U argument to imapd(8).

## 2. Maximum child count

By default, Cyrus is allowed to spawn a limitless number of child imapd processes. To control this growth, adjust the maxchild option in cyrus.conf(5).

## 3. Clean up connections that are no longer in use

While POP connections are short lived, IMAP connections can be long lived. And then there are processes trying to listen to a client that’s no longer alive.

Setting tcp_keepalive option in imapd.conf(5) to 1 can be used to test if connections are still alive. The operating system will send an ACK packet every so often (every 2 hours by default on Linux) which tests if the TCP endpoint is still reachable.

The other tcp_keepalive_ options help control how and when the test occurs.