Dynatrace Load - Dynatrace Load lets you test the performance of web and mobile applications with the realism of load generation from the cloud.

UMLGraph - UMLGraph is a professional automated drawing tool that allows the designers the declarative specification and drawing of UML class and sequence diagram.

Apache JMeter - Apache JMeter™.

yEd - yEd is a free desktop application to quickly create, import, edit, and automatically arrange diagrams. It runs on Windows, Mac OS X, and Unix/Linux.

Sitespeed - Sitespeed.io is an open source tool that helps to analyze and optimize website speed and performance.

Dia - Dia is a GTK+ based diagram creation program for GNU/Linux, MacOS X, Unix, and Windows, and is released under the GPL license.