bloat_summary.py

import sys
from collections import defaultdict

with open(sys.argv[1]) as f:
    lines = (ln.strip() for ln in f)
    # Skip headers.
    assert next(lines).startswith("File")
    # Sum up serde-related things vs total.
    totalSize = 0
    sizeByCrate = defaultdict(int)
    sizeFromSerdeByCrate = defaultdict(int)
    for ln in lines:
        # The output ends with a summary, which isn't useful to us.
        if ".text section size" in ln:
            break
        (_, _, size, crate, name) = ln.split(None, 4)
        if size.endswith("KiB"):
            size = int(float(size[:-3]) * 1024)
        elif size.endswith("B") and size[-2].isdigit():
            size = int(size[:-1])
        else:
            assert False, "Unable to parse size {!r}".format(size)
        # Ignore symbols from non-rust dependencies, and things that won't
        # be relevant to us when vendoring into Firefox..
        if crate in ("[Unknown]", "std", "nss_sys"):
            continue
        totalSize += size
        sizeByCrate[crate] += size
        if "serde" not in crate and "serde" in name.lower():
            sizeFromSerdeByCrate[crate] += size
    # What's the damage?
    for (size, crate) in sorted(((size, crate) for (crate, size) in sizeByCrate.items()), reverse=True):
        print("{:<6} of {:<6} bytes ({:.2f}%) come from {!r}".format(
          size,
          totalSize,
          (size / totalSize) * 100,
          crate,
        ))
        if sizeFromSerdeByCrate[crate]:
            print("                 of which {:<6} bytes ({:.2f}%) from serde derives".format(
                sizeFromSerdeByCrate[crate],
                (sizeFromSerdeByCrate[crate] / size) * 100,
            ))