"Less Slow C++" offers practical advice for improving C++ build and execution speed. It covers techniques ranging from precompiled headers and unity builds (combining source files) to link-time optimization (LTO) and profile-guided optimization (PGO). It also explores build system optimizations like using Ninja and parallelizing builds, and coding practices that minimize recompilation such as avoiding unnecessary header inclusions and using forward declarations. Finally, the guide touches upon utilizing tools like compiler caches (ccache) and build analysis utilities to pinpoint bottlenecks and further accelerate the development process. The focus is on readily applicable methods that can significantly improve C++ project turnaround times.
UTL::profiler is a single-header, easy-to-use C++17 profiler that measures the execution time of code blocks. It supports nested profiling, multi-threaded applications, and custom output formats. Simply include the header, wrap the code you want to profile with UTL_PROFILE macros, and link against a high-resolution timer if needed. The profiler automatically generates a report with hierarchical timings, making it straightforward to identify performance bottlenecks. It also provides the option to programmatically access profiling data for custom analysis.
HN users generally praised the profiler's simplicity and ease of integration, particularly appreciating the single-header design. Some questioned its performance overhead compared to established profilers like Tracy, while others suggested improvements such as adding timestamp support and better documentation for multi-threaded profiling. One user highlighted its usefulness for quick profiling in situations where integrating a larger library would be impractical. There was also discussion about the potential for false sharing in multi-threaded scenarios due to the shared atomic counter, and the author responded with clarifications and potential mitigation strategies.
The Go Optimization Guide at goperf.dev provides a practical, structured approach to optimizing Go programs. It covers the entire optimization process, from benchmarking and profiling to understanding performance characteristics and applying targeted optimizations. The guide emphasizes data-driven decisions using benchmarks and profiling tools like pprof and highlights common performance bottlenecks in areas like memory allocation, garbage collection, and inefficient algorithms. It also delves into specific techniques like using optimized data structures, minimizing allocations, and leveraging concurrency effectively. The guide isn't a simple list of tips, but rather a comprehensive resource that equips developers with the methodology and knowledge to systematically improve the performance of their Go code.
Hacker News users generally praised the Go Optimization Guide linked in the post, calling it "excellent," "well-written," and a "great resource." Several commenters highlighted the guide's practicality, appreciating the clear explanations and real-world examples demonstrating performance improvements. Some pointed out specific sections they found particularly helpful, like the advice on using sync.Pool and understanding escape analysis. A few users offered additional tips and resources related to Go performance, including links to profiling tools and blog posts. The discussion also touched on the nuances of benchmarking and the importance of considering optimization trade-offs.
Meta developed Strobelight, an internal performance profiling service built on open-source technologies like eBPF and Spark. It provides continuous, low-overhead profiling of their C++ services, allowing engineers to identify performance bottlenecks and optimize CPU usage without deploying special builds or restarting services. Strobelight leverages randomized sampling and aggregation to minimize performance impact while offering flexible filtering and analysis capabilities. This helps Meta improve resource utilization, reduce costs, and ultimately deliver faster, more efficient services to users.
Hacker News commenters generally praised Facebook/Meta's release of Strobelight as a positive contribution to the open-source profiling ecosystem. Some expressed excitement about its use of eBPF and its potential for performance analysis. Several users compared it favorably to other profiling tools, noting its ease of use and comprehensive data visualization. A few commenters raised questions about its scalability and overhead, particularly in large-scale production environments. Others discussed its potential applications beyond the initially stated use cases, including debugging and optimization in various programming languages and frameworks. A small number of commenters also touched upon Facebook's history with open source, expressing cautious optimism about the project's long-term support and development.
The blog post argues for a more holistic approach to debugging and performance analysis by combining various tools and data sources. It emphasizes the limitations of isolated tools like memory profilers, call graphs, exception reports, and telemetry, advocating instead for integrating them to provide "system-wide context." This richer context allows developers to understand not only what went wrong, but also why and how, enabling more effective and efficient troubleshooting. The post uses a fictional scenario involving a slow web service to illustrate how correlating data from different tools can pinpoint the root cause of a performance issue, which in their example turns out to be an unexpected interaction between a third-party library and the application's caching strategy.
Hacker News users discussed the blog post about system-wide context, focusing primarily on the practical challenges of implementing such a system. Several commenters pointed out the difficulty of handling circular dependencies and the potential performance overhead, particularly in garbage-collected languages. Some suggested alternative approaches like structured logging and distributed tracing, while others questioned the overall value proposition compared to existing debugging tools. The complexity of integrating with different programming languages and the potential for information overload were also raised as concerns. A few commenters expressed interest in the idea but acknowledged the significant engineering effort required to make it a reality. One compelling comment highlighted the potential benefits for debugging complex, distributed systems, where understanding the interplay of different components is crucial.
Perforator is an open-source, cluster-wide profiling tool developed by Yandex for analyzing performance in large data centers. It uses hardware performance counters to collect low-overhead, detailed performance data across thousands of machines simultaneously, aiming to identify performance bottlenecks and optimize resource utilization. The tool offers a web interface for visualization and analysis, and allows users to drill down into specific nodes and processes for deeper investigation. Perforator supports various profiling modes, including CPU, memory, and I/O, and can be integrated with existing monitoring systems.
Several commenters on Hacker News expressed interest in Perforator, particularly its ability to profile at scale and its low overhead. Some questioned the choice of Python for the agent, citing potential performance issues, while others appreciated its ease of use and integration with existing Python-based infrastructure. A few commenters compared it favorably to existing tools like BCC and eBPF, highlighting Perforator's distributed nature as a key differentiator. The discussion also touched on the challenges of profiling in production environments, with some sharing their experiences and suggesting potential improvements to Perforator. Overall, the comments indicated a positive reception to the tool, with many eager to try it in their own environments.
The article "The Mythical IO-Bound Rails App" argues that the common belief that Rails applications are primarily I/O-bound, and thus not significantly impacted by CPU performance, is a misconception. While database queries and external API calls contribute to I/O wait times, a substantial portion of a request's lifecycle is spent on CPU-bound activities within the Rails application itself. This includes things like serialization/deserialization, template rendering, and application logic. Optimizing these CPU-bound operations can significantly improve performance, even in applications perceived as I/O-bound. The author demonstrates this through profiling and benchmarking, showing that seemingly small optimizations in code can lead to substantial performance gains. Therefore, focusing solely on database or I/O optimization can be a suboptimal strategy; CPU profiling and optimization should also be a priority for achieving optimal Rails application performance.
Hacker News users generally agreed with the article's premise that Rails apps are often CPU-bound rather than I/O-bound, with many sharing anecdotes from their own experiences. Several commenters highlighted the impact of ActiveRecord and Ruby's object allocation overhead on performance. Some discussed the benefits of using tools like rack-mini-profiler and flamegraphs for identifying performance bottlenecks. Others mentioned alternative approaches like using different Ruby implementations (e.g., JRuby) or exploring other frameworks. A recurring theme was the importance of profiling and measuring before optimizing, with skepticism expressed towards premature optimization for perceived I/O bottlenecks. Some users questioned the representativeness of the author's benchmarks, particularly the use of SQLite, while others emphasized that the article's message remains valuable regardless of the specific examples.
bpftune is a new open-source tool from Oracle that leverages eBPF (extended Berkeley Packet Filter) to automatically tune Linux system parameters. It dynamically adjusts settings related to networking, memory management, and other kernel subsystems based on real-time workload characteristics and system performance. The goal is to optimize performance and resource utilization without requiring manual intervention or system-specific expertise, making it easier to adapt to changing workloads and achieve optimal system behavior.
Hacker News commenters generally expressed interest in bpftune and its potential. Some questioned the overhead of constantly monitoring and tuning, while others highlighted the benefits for dynamic workloads. A few users pointed out existing tools like tuned-adm, expressing curiosity about bpftune's advantages over them. The project's novelty and use of eBPF were appreciated, with some anticipating its integration into existing performance tuning workflows. A desire for clear documentation and examples of real-world usage was also expressed. Several commenters were specifically intrigued by the network latency use case, hoping for more details and benchmarks.
Summary of Comments ( 18 )
https://news.ycombinator.com/item?id=43727743
Hacker News users discussed the practicality and potential benefits of the "less_slow.cpp" guidelines. Some questioned the emphasis on micro-optimizations, arguing that focusing on algorithmic efficiency and proper data structures is generally more impactful. Others pointed out that the advice seemed tailored for very specific scenarios, like competitive programming or high-frequency trading, where every ounce of performance matters. A few commenters appreciated the compilation of optimization techniques, finding them valuable for niche situations, while some expressed concern that blindly applying these suggestions could lead to less readable and maintainable code. Several users also debated the validity of certain recommendations, like avoiding virtual functions or minimizing branching, citing potential trade-offs with code design and flexibility.
The Hacker News post titled "Less Slow C++" (https://news.ycombinator.com/item?id=43727743) sparked a discussion with a moderate number of comments, largely focusing on the practicality and nuances of the advice offered in the linked GitHub repository.
Several commenters appreciated the author's effort to collect and present performance optimization tips. One user highlighted the value in consolidating such information, especially for those newer to C++, acknowledging that while experienced developers might be familiar with many of the tips, having them readily available in one place is beneficial.
However, a recurring theme in the comments was the caution against premature optimization. Multiple users emphasized that focusing on code clarity and correctness should precede optimization efforts. They argued that optimizing without proper profiling and understanding of actual bottlenecks can be counterproductive, leading to more complex code without significant performance gains. One commenter even suggested the title should be "Faster C++," as "Less Slow" implies a focus on fixing slowness rather than writing efficient code from the start.
Some commenters delved into specific points from the GitHub document. There was discussion around the use of
std::vectorversusstd::array, pointing out thatstd::arrayis often preferable for small, fixed-size collections due to its avoidance of heap allocation. Another discussion centered on the advice to avoid exceptions, with some agreeing on their performance overhead, especially when thrown frequently, while others argued that exceptions are crucial for error handling and shouldn't be dismissed solely for performance reasons.The topic of inlining also garnered attention. While the GitHub document recommends strategic use of inlining, some commenters elaborated on the compiler's role in inlining decisions. They highlighted that modern compilers are often better at determining which functions to inline, making explicit inlining less necessary and sometimes even detrimental.
Finally, a few commenters shared their own experiences and preferred optimization techniques, adding further depth to the conversation. One mentioned the importance of considering data locality and cache efficiency for performance-critical code.
Overall, the comments section provides a balanced perspective on C++ optimization. While acknowledging the usefulness of the compiled tips, the discussion emphasizes the importance of careful profiling, prioritizing code readability, and understanding the trade-offs involved in different optimization strategies. It serves as a reminder that blindly applying performance tweaks without proper consideration can often do more harm than good.