Avoid negative values in malloc_utils metrics (#2692)
Avoid negative values in malloc_utils metrics (#2692)

## Proposed Changes

While investigating memory usage I noticed that the malloc metrics were going negative once they passed 2GiB. This is because the underlying `mallinfo` function returns a `i32`, and we were casting it straight to an `i64`, preserving the sign.

The long-term fix will be to move to `mallinfo2`, but it's still not yet widely available.




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