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Japanese version: https://youtu.be/iDW93fAp2I8 How do instance variables work? We've all used instance variables in our programs, but how do they actually work? In this presentation we'll look at how instance variables are implemented in Ruby. We'll start with a very strange benchmark, then dive in to Ruby internals to understand why the code behaves the way it does. Once we've figured out this strange behavior, we'll follow up with a patch to increase instance variable performance. Be prepared for a deep dive in to a weird area of Ruby, and remember: don't @ me!
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In this presentation titled "Don't @ me! Instance Variable Performance in Ruby," Aaron Patterson delves into the intricate workings of instance variables in Ruby, aiming to enhance their performance through a deeper understanding of Ruby's internals. The session begins with Patterson reminiscing about his previous Japanese presentation, humorously noting his self-interpretation as he transfers the content to an English audience. The key points covered in the talk include: - **Instance Variable Fundamentals**: Patterson explains what instance variables are and how they function within Ruby. He sets a baseline for understanding by discussing a peculiar benchmark that reveals the complexities of instance variable behavior. - **Ruby 2.7 Enhancements**: The introduction of a new feature called GC compact is highlighted, enabling memory conservation through compaction, which functions akin to the defragmentation of hard drives. Patterson illustrates this process with graphs showing memory layout before and after compaction. - **Compaction Process**: A detailed explanation is provided on the mechanics of the compaction process using pointers, which manipulate memory space. The ultimate goal is to save memory automatically, allowing developers to work without needing to be aware of the garbage collection compaction running in the background. - **Concurrency Challenges**: Patterson discusses the existing challenges with ensuring compaction runs concurrently without causing issues. The manual requirement from developers to invoke GC compact is addressed, pointing out its limitation in terms of automatic functionality and speed. - **Implementation of Read Barriers**: To solve the internal complexity that arises during class deletions and references, read barriers are introduced. Patterson illustrates how these barriers ensure stability and memory integrity within Ruby's garbage collection process. - **Memory Management Improvements**: The presentation culminates with the introduction of memory protection strategies, such as the 'mprotect' system call for managing memory more effectively. Patterson shares outcomes from benchmarks indicating memory usage improvements displayed in practical scenarios like RDoc documentation generation. In conclusion, Patterson encapsulates his findings by stating that by harnessing deeper insights into Ruby's memory management, significant advancements can be made. This project, while still in progress, lays the groundwork for future efficiency in Ruby's instance variable handling, emphasizing the relationship between memory usage and performance optimization. The talk sets an anticipatory tone for future enhancements, with Patterson expressing enthusiasm for Ruby's developments leading to Ruby 2021.
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