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Hello, everyone. Thank you for being here today.
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Today, I'm going to talk about hacking and profiling Ruby for performance.
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My name is Daisuke Aritomo, but my friends call me also you. I'm a member of Rubik NOC, which is a Network Operation Center.
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It's similar to a Wi-Fi team, and I’ve been involved in dragging cables here and there since Day Zero. Additionally, I work at Cookpad.
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Let me quickly introduce Cookpad. Did anyone notice the refrigerators over there? Those are actually from Cookpad.
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The Ruby code controls the locks on these refrigerators. If anyone wants to build Ruby-powered refrigerators, join us! We're also organizing a work-pack Rubik event in Tokyo on May 18, which includes a hands-on part. If you're excited, please visit the Cookpad sponsor booth for details.
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Now, let's start talking about the actual content of this talk. I'm going to discuss how to profile and tune a Ruby web application in just eight hours as part of a performance tuning competition for fun.
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First, how many of you love the word 'performance'? Yes, everyone loves performance! There's actually a performance challenge competition called Ifcon. Contestants are given three virtual machines, infinite computing resources, and a very low-performing web application.
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The app is so slow that it is practically unusable. Contestants have eight hours to improve its performance. They may also request a 50-second benchmark during the contest to see their progress.
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When a benchmark is requested, the benchmarking server will run a large number of HTTP requests to the Ruby application, and the benchmark results will determine the contestants' scores.
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The team with the highest score wins. There was another talk related to this contest, which was done today. I recommend checking it out afterward, as all talks will be available on YouTube.
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The contestants are provided with a Ruby application implemented using Sinatra, running on Puma with Nginx included. My FQL (Fine Query Language) is also on the server, and alternate implementations of the same app in other languages like Python, Go, and Node.js are also included.
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Initially, the performance is quite poor. The challenge is to make the web app server as fast as possible within eight hours, but contestants cannot scale up their servers or purchase more servers. They can only use their skills to optimize the existing application.
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The main loop involves hacking around the Ruby code, running benchmarks, and trying to improve scores repeatedly. The aim is to achieve the highest score, and while there are many aspects to improve performance, today I will focus on what can be done during Ifcon.
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One of the reasons Ruby is a great language to compete with in Ifcon is due to certain libraries available and how to effectively profile code. It's essential to track down and utilize Ruby's profiling features for optimal performance.
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I won't be discussing configuring Nginx or Linux today, despite their importance in achieving a good score in Ifcon. This presentation focuses primarily on Ruby. However, we'll touch upon monitoring at the system level and preparations you need for your recipes.
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There are many aspects we could explore, such as effective RDBMS indexes, optimizing queries, and avoiding N+1 issues. N+1 issues occur when queries are executed in loops, leading to unnecessary overhead.
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Replacing sub-optimal algorithms, optimizing server resources, caching, and upgrading to the latest Ruby version are also crucial steps. Ruby 3.0 and onward are touted as among the fastest versions.
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Now, where should we start our optimization efforts? It's crucial to identify where to focus our hacking. Performance profiling will guide us on what areas need improvement.
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Before we dive into profiling, let me explain why Ruby is a superb language for this competition. In this contest, you might encounter somewhere between 500 to 800 lines of network code. Understanding this code completely in eight hours can be quite daunting.
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Fortunately, Ruby's syntax is quite compact, making it easier to read and comprehend within this limited time frame.
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Ruby also provides many helpful methods and classes like `array`, `hash`, and `enumerable`, which can assist in performing queries effectively. This can significantly improve both coding and debugging efficiency.
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For the competition, one of my preferred techniques is monkey patching. It's a great tool to adjust methods on the fly and adapt them to achieve better performance.
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However, let's shift back to performance challenges in Ruby. There may be instances where you encounter 'no method error' after starting benchmarking, indicating a typo or an unrecognized method in your code.
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No matter where this error occurs, it is fixable. It's a matter of carefully reviewing your code. Furthermore, tools like 'RBS' and type checking can help mitigate such issues.
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Performance tuning in Ruby can be understood through three primary points: profiling accurate bottlenecks, effectively utilizing CPU resources, and achieving high concurrency.
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Before making random improvements, it's crucial to measure the changes' impact accurately. Random optimizations can lead to minor gains, but deliberate profiling will provide a clearer picture of where improvements are truly needed.
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Fortunately, there are many profiling tools available in Ruby, ranging from line profilers that track every single function call to sampling profilers which collect data at defined intervals. These profilers can help identify performance bottlenecks.
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Tools like 'stackprof' and 'rbx5' are excellent options for sampling. Sampling profilers have lower performance overhead while providing insightful analysis.
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If you're profiling, visualizing your profiling results can also be beneficial. One common visual representation is the flame graph, which displays time consumption across various functions in the application.
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Each bar in the flame graph represents a function, and the length of the bar indicates how much time that function consumed.
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If a bar is particularly long, that indicates potential room for optimization. For instance, if you notice that a network handler function has a long execution time, it may be time to analyze and optimize that specific part of the code.
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Let's dive deeper into profiling internals.
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The `rb_profile_frames` method is a powerful aspect of Ruby profiling. It returns the call stack of the currently executing thread, allowing us to see precisely what was happening when performance measurements were taken.
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When using multiple threads, results may not always reflect a complete view of the entire system. For example, if one method overlaps in execution time with other threaded operations, it may appear less significant.
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In this context, threading adds complexity. Only one thread can access the CPU at a particular time due to the GVL. Other threads can perform IO operations, leading to confusion in profiling results.
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My next point is maximizing CPU utilization in Ruby. As previously mentioned, Ruby's GVL means that even if you create multiple threads, only one can be executing Ruby code at a time. In this structuring, important strategies like using multiple processes can be beneficial.
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For example, if you want to achieve CPU parallelism, consider implementing multiple processes instead of relying merely on threads, as they are not necessarily efficient in Ruby.
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Memory management also plays a vital role in this balance. When employing multiple processes, higher memory consumption is inevitable. Your goal should always be to find the best performance ratio between processes and threads.
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To summarize, many beneficial features exist to enable performance improvements in Ruby applications, such as the internal event handling functionalities which could assist in achieving better resource management.
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As we wrap this session, remember that Ruby's performance potential lies in its ability to utilize concurrency effectively, which can be a game changer in competitions like Ifcon.
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Let us remember the significance of performance profiling combined with accurate measurements, as it is crucial to circumstances like the performance contests we talked about today.
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Thank you for your attention. I hope you find this session informative and useful for your Ruby programming endeavors. Acknowledgments to my teammates and colleagues who've provided additional advice and support.
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It's been a pleasure sharing my insights with you today. Thank you for being such an attentive audience!
