Excimer is a PHP 7.1+ extension that provides a non-static, non-global profiler for PHP. It is intended as a replacement for Xhprof. More details can be found at phab:T205059 (TODO: Move that design documentation here).
Download the source code into an appropriate directory from git:
git clone https://gerrit.wikimedia.org/r/mediawiki/php/excimer.git
excimer here is the directory that excimer git repository was cloned to.
cd excimer phpize && ./configure && make && sudo make install
extension=excimer.so to the PHP configuration in an appropriate place. For example, in modern Debian-derived distributions you'd add a file to
$version is the version of PHP for which you compiled Excimer) and use the
phpenmod command to enable it.