Deno.systemMemoryInfo().available and Deno.systemMemoryInfo().free are incorrect on macOS

[brettchalupa]

Version: Deno 2.1.4
OS: macOS 14.6 (Sonoma)

I copied the example for reading system metrics (https://docs.deno.com/examples/reading_system_metrics/) to test it and noticed that Deno.systemMemoryInfo().available and Deno.systemMemoryInfo().free appear to be ~1000x smaller than they should be.

Total Memory: 16384 MB

what Deno.systemMemoryInfo() reports - deno 2.1.4
Free Memory: 0.102996826171875 MB
Available Memory: 4.8754119873046875 MB
Used Memory: 16379.124588012695 MB

corrected for macOS:
Free Memory: 105.46875 MB
Available Memory: 4992.421875 MB
Used Memory: 11391.578125 MB

Deno 2.1.4 Wrong Percentage: 99.97%
macOS Corrected Percentage: 69.53%

The corrected values are more accurate to what I see in macOS Activity Monitor and when running a similar Rust program with the sysinfo crate.

Repro Steps

deno run --allow-sys https://gist.githubusercontent.com/brettchalupa/62e489396ae4cf87ee59517fcc0880c4/raw/34d8cc2908644bd458dec5b4894f6468ba9644e4/deno_ram_check_bug.ts

View the Gist source.

Zoom into the problem code and fix for macOS:

console.log("what Deno.systemMemoryInfo() reports - deno 2.1.4");
console.log(`Free Memory: ${toMB(memoryInfo.free)} MB`);
console.log(`Available Memory: ${toMB(memoryInfo.available)} MB`);
console.log(
  `Used Memory: ${toMB(memoryInfo.total - memoryInfo.available)} MB`,
);

console.log("\ncorrected for macOS:");
console.log(`Free Memory: ${toMB(memoryInfo.free * 1024)} MB`);
console.log(`Available Memory: ${toMB(memoryInfo.available * 1024)} MB`);
console.log(
  `Used Memory: ${toMB(memoryInfo.total - memoryInfo.available * 1024)} MB`,
);

I'm not 100% sure whether the multiplication needs to be * 1024 or * 1000.

Additional Notes

• I confirmed the values reported by Deno.systemMemoryInfo().available and .free are correct on Fedora Linux
• I confirmed this isn't an issue on Windows 11 (although .available reports 0, but .free seems to be correct

See Also

• Deno.systemMemoryInfo().available and (node:os).freemem() is off by x1000 #25497
• fix(ext/node): report freemem() on Linux in bytes #25511
• os.freemem() pollyfill is not compatible with Node.js #21148
• systemMemoryInfo doesn't work completely cross platform #13724