Oink - Oink is a Rails plugin and log parser to help narrow down the source(s) of increased memory usage in rails applications.
JProfiler - JProfiler is the leading Java Profiler for profiling on the JVM. JProfiler's intuitive UI helps you resolve performance bottlenecks, pin down memory leaks and understand threading issues.
Munin - PnP networked resource monitoring tool that can help to answer the what just happened to kill our performance
VisualVM - VisualVM is a visual tool integrating several commandline JDK tools and lightweight profiling...
Derailed Benchmarks - Derailed Benchmarks is a benchmarking tool for Rails.
dotMemory - dotMemory allows users to analyze memory usage in a variety of .NET and .NET Core applications.