Answer by nethawk for I use PKI token,and I run keystone in apache. When I test the performance of keystone(using POST /tokens),I found it will create many processes like this: apache 2970 2242 0 17:17 ? 00:00:00 openssl cms -sign -signer /etc/keystone/ssl/certs/signing_cert.pem -inkey /etc/keystone/ssl/private/signing_key.pem -outform PEM -nosmimecap -nodetach -nocerts -noattr And the max nunmber of these processes is 195. Once these processes are createed,they will not be closed until I kill them. But when I test a single API or login from dashboard, there is no such process. If I do not run keystone in apache,there is also no these processes. That's Why?

Today,I have already know the reason of this question. Openssl is thread-unsafe,so I must start multi apache processes but sigle thread.