How can we use valgrind or memwatch for in‐depth memory analysis in k6? - shiviyer/Blogs GitHub Wiki

Using valgrind or memwatch for in-depth memory analysis of a K6 process is a bit tricky since K6 is written in Go, and these tools are typically used for C/C++ applications. However, valgrind can still provide some insights. Here's how to approach this:

Using Valgrind with K6

  1. Install Valgrind:

    • Ensure valgrind is installed on your system. You can usually install it via your package manager, for example, sudo apt-get install valgrind on Debian-based systems.

  2. Run K6 with Valgrind:

    • Since K6 is a compiled Go binary, direct usage of valgrind might not yield easily interpretable results due to Go's runtime and garbage collector. However, you can still run it: 
      valgrind --leak-check=full --show-leak-kinds=all k6 run yourscript.js
    • This command runs K6 under valgrind with options to check for all types of memory leaks.

  3. Interpreting the Results:

    • The output from valgrind will include information about memory allocations that were not freed.
    • Note that Go's runtime might show some "still reachable" allocations which are not necessarily leaks but rather memory managed by Go's garbage collector.

  4. Limitations:

    • The data from valgrind in the context of a Go application might be overwhelming and filled with noise due to the nature of Go’s memory management.
    • It’s crucial to understand Go's garbage collection and memory management to interpret the results correctly.

Using Memwatch (or Similar Tools)

memwatch is more suited for C/C++ applications, and using it with Go programs (like K6) is not straightforward or recommended. For Go applications, you would typically use Go's built-in profiling tools:

  1. Enable Profiling in K6:

    • K6 has built-in support for CPU and memory profiling. You can enable this by setting environment variables or flags when starting your K6 tests.
    • Example for memory profiling: 
      k6 run --out influxdb=http://localhost:8086/myk6db yourscript.js --vus 10 --duration 30s

  2. Analyze Profile with Go Tools:

    • The generated profile can be analyzed using Go’s pprof tool.
    • This gives you insights into memory allocations, garbage collection, and potential memory hotspots.

  3. Consult K6 Documentation:

    • Refer to the K6 documentation for specific instructions on enabling and using these profiling features.

General Recommendations

  • Update K6: Ensure you’re using the latest version of K6, as updates may include performance improvements or bug fixes.
  • Consult Documentation and Community: Check K6 documentation for guidance on profiling and memory analysis. The K6 community may also have specific advice for memory leak detection.

Using these tools and techniques, you should be able to conduct a detailed analysis of memory usage in K6 and identify any potential memory leaks or inefficiencies.