Apache JMeter - Apache JMeter™.
TestRail - TestRail provides comprehensive test case management for software testing. Organize your testing, boost productivity, get real-time insights, and track progress toward milestones. Integrates with leading issue tracking and test automation tools.
Selenium - Selenium automates browsers. That's it! What you do with that power is entirely up to you. Primarily, it is for automating web applications for testing purposes, but is certainly not limited to just that.
Kualitee - Your next ALM alternative for Requirements planning, test case management, and issue tracking for both manual and automated testing.
locust - An open source load testing tool written in Python.
Buildkite - Buildkite is a platform for running fast, secure, and scalable continuous integration pipelines on your own infrastructure.