Ruby bindings to RE2, "a fast, safe, thread-friendly alternative to backtracking regular expression engines like those used in PCRE, Perl, and Python".

TinyTDS - A modern, simple and fast FreeTDS library for Ruby using DB-Library. Developed for the ActiveRecord SQL Server adapter.

The Libxml-Ruby project provides Ruby language bindings for the GNOME Libxml2 XML toolkit. It is free software, released under the MIT License. Libxml-ruby's primary advantage over REXML is performance - if speed is your need, these are good libraries to consider, as demonstrated by the informal benchmark below.

The Helix Runtime

pass binding of method caller implicitly

A lightweight library for real-time, consistent and scalable coordination of events.

Monitors Ruby apps and reports detailed metrics on performance to Scout.

This Ruby C extenstion defines a module that can be included into ChunkyPNG to improve its speed.

A Ruby program to facilitate accessing Aliyun Object Storage Service

Cool.io provides a high performance event framework for Ruby which uses the libev C library

rblineprof shows you lines of code that are slow.

String#scrub for Ruby 2.0.0 and 1.9.3

debugger is a fast implementation of the standard Ruby debugger debug.rb. It is implemented by utilizing a new Ruby C API hook. The core component provides support that front-ends can build on. It provides breakpoint handling, bindings for stack frames among other things.

An LL(1) parser generator for Ruby.

Psych is a YAML parser and emitter. Psych leverages libyaml[http://pyyaml.org/wiki/LibYAML] for its YAML parsing and emitting capabilities. In addition to wrapping libyaml, Psych also knows how to serialize and de-serialize most Ruby objects to and from the YAML format.

pycall

Skylight is a smart profiler for Rails, Sinatra, and other Ruby apps.

Simple wrapper around the pHash library

ruby-opencv is a wrapper of OpenCV for Ruby. It helps you to write computer vision programs (e.g. detecting faces from pictures) with Ruby.

Parses SQL queries using a copy of the PostgreSQL server query parser