Skip to content

Latest commit

 

History

History
54 lines (45 loc) · 2.11 KB

MemoryLayout.md

File metadata and controls

54 lines (45 loc) · 2.11 KB
Raw

Extracting the Internal GraalWasm Memory Layout Based on a Given WebAssembly Program

GraalWasm contains a tool for extracting the internal memory layout for a given WebAssembly application. This is useful for detecting the causes of memory overhead.

To execute the memory layout extractor, run:

$ mx --dy /compiler wasm-memory-layout -Djol.magicFieldOffset=true -- [wasm-file]

This prints the memory layout tree of the given file to the console. The application provides additional options:

  • --warmup-iterations: to set the number of warmup iterations.
  • --entry-point: to set the entry point of the application. This is used to perform linking
  • --output: to extract the memory layout into a file instead of the console.

You can also pass all other options available in GraalWasm such as --wasm.Builtins=wasi_snapshot_preview1.

The resulting tree represents a recursive representation of the Objects alive in GraalWasm starting from the WasmContext. The output looks similar to this:

-context: 6598280 Byte [100%]
  -equivalenceClasses: 1320 Byte [0%]
    -table: 80 Byte [0%]
    -table[0]: 384 Byte [0%]
      -key: 72 Byte [0%]
        -paramTypes: 24 Byte [0%]
        -resultTypes: 24 Byte [0%]
      -next: 280 Byte [0%]
        -key: 64 Byte [0%]
          -paramTypes: 24 Byte [0%]
          -resultTypes: 16 Byte [0%]
        -next: 184 Byte [0%]
          -key: 56 Byte [0%]
            -paramTypes: 16 Byte [0%]
            -resultTypes: 16 Byte [0%]
          -next: 96 Byte [0%]
            -key: 64 Byte [0%]
              -paramTypes: 24 Byte [0%]
              -resultTypes: 16 Byte [0%]
    -table[2]: 208 Byte [0%]
      -key: 72 Byte [0%]
        -paramTypes: 24 Byte [0%]
        -resultTypes: 24 Byte [0%]
      -next: 104 Byte [0%]
...

The names represent the names of fields in classes. For example equivalenceClasses is a field in WasmContext. The values next to the names represent the absolute amount of memory in bytes while the number in brackets represent the relative contribution to the overall memory overhead. Names with indices represent array entries such as table[0].