ab

sudo apt install apache2-utils
ab -c 100 -n 1000 -k https://www.baidu.com/

-c means how many users send requests at the SAME time. -n means the total requests to be sent in this benchmark. -k means keep-alive.

See its manpage for details.

Ref: http://stackoverflow.com/questions/12732182/ab-load-testing

Install with yum install httpd-tools on CentOS. See http://serverfault.com/questions/514401/how-to-install-apache-benchmark-on-centos for details.