JVM Performance Engineering: Inside OpenJDK and the HotSpot Java Virtual Machine by Monica Beckwith

Author:Monica Beckwith
Language: eng
Format: epub
Publisher: Pearson
Published: 2024-07-15T00:00:00+00:00

System Profilers and Performance Monitoring Units

Within the realm of performance engineering, system profilers—such as perf, OProfile, Intel’s VTune Profiler, and other architecture-geared profilers—provide invaluable insights into hardware’s functioning that can help developers optimize both system and application performance. They interact with the hardware subsystem to provide a comprehensive view that is unattainable through standard monitoring tools alone.

A key source of data for these profilers is the performance monitoring units (PMUs) within the CPU. PMUs, including both fixed-function and programmable PMUs, provide a wealth of low-level performance information that can be used to identify bottlenecks and optimize system performance.

System profilers can collect data from PMUs to generate a detailed performance profile. For example, the perf command can be used to sample CPU stack traces across the entire system, creating a “flat profile” that summarizes the time spent in each function across the entire system. This kind of performance profile can be used to identify functions that are consuming a disproportionate amount of CPU time. By providing both inclusive and exclusive times for each function, a flat profile offers a detailed look at where the system spends its time.

However, system profilers are not limited to CPU performance; they can also monitor other system components, such as memory, disk I/O, and network I/O. For example, tools like iostat and vmstat can provide detailed information about disk I/O and memory usage, respectively.

Once we have identified problematic patterns, bottlenecks, or opportunities for improvement through monitoring stats, we can employ these advanced profiling tools for deeper analysis.

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