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Twitter MySQL 5.5

This is Twitter's MySQL development branch, which is based on MySQL 5.5 as published by Oracle on MySQL on Launchpad.

This repository is published in order to share code and information and is not intended to be used directly outside of Twitter. We provide no guarantees of bug fixes, ongoing maintenance, compatibility, or suitability for any user outside of Twitter.

The original README file provided with the upstream MySQL release can be found at README-MySQL.

Features in Twitter MySQL

Additional status variables

Additional status variables have been added, particularly from the internals of InnoDB. This allows us to monitor our systems more effectively and understand their behavior better when handling production workloads. The variables added are:

Optimization of memory allocation under NUMA

On most recent multi-processor systems, a non-uniform memory access NUMA (NUMA) architecture is in use, which divides the total system memory across multiple NUMA "nodes". When allocating large amounts of memory to InnoDB's buffer pool, as is typical, some inefficiencies as well as serious problems can be encountered. More details about the problems typical in NUMA systems running MySQL can be found in a blog post by Jeremy Cole. The following changes have been made to optimize and improve this:

Server-side query timeout

Buffer pool export and restore by prefetch

Optimization for solid-state drives (SSDs)