The article explains why System.currentTimeMillis() is unsuitable for measuring code execution duration, demonstrates its non‑monotonic behavior and potential for negative results, and shows that System.nanoTime() provides a reliable, high‑resolution, monotonic timer for accurate performance analysis.
After observing a middleware that caches System.currentTimeMillis, the author investigates whether this method truly suffers performance issues, debunks common myths with detailed analysis, benchmarks using custom and JMH tests, and concludes that System.currentTimeMillis performs adequately without needing custom caching.
The article explains that System.currentTimeMillis()—a common Java API for timestamps—can become dramatically slower when called concurrently or very frequently, analyzes the native implementation causing the slowdown, and presents a cached‑clock solution to mitigate the performance issue.
This article investigates whether System.currentTimeMillis suffers from performance problems by examining custom caching implementations, analyzing common misconceptions, presenting benchmark data from both simple loops and JMH tests, and concluding that the native method is sufficiently fast for typical use cases.
This article investigates the implementation of Java's System.currentTimeMillis() on Windows, macOS, and Linux, measures its execution speed, explores the underlying native methods and OS time‑source mechanisms such as TSC, HPET, and RTC, and discusses performance implications and best practices for high‑frequency timestamp retrieval.
The article reveals that frequent or concurrent calls to Java's System.currentTimeMillis can become dramatically slower due to kernel transitions and clock‑source contention, demonstrates the slowdown with benchmark code, explains the native gettimeofday implementation, and proposes a cached‑timestamp solution using a single scheduler thread.
System.currentTimeMillis() appears fast but under heavy concurrent calls it becomes dramatically slower due to kernel‑mode time‑of‑day queries, and this article explains the root cause, shows benchmark results, and offers a cached‑timestamp solution to restore performance.
