I'm testing[1] that if we make a fast path that detect if keys is `empty_keys_struct` inside `dictresize`. It can be faster than original patch, but still slower than default (unpatch) in most case.


➜  cpython git:(compact_empty_dict) ✗ ./python.default -m perf compare_to -G --min-speed=1 default.json lpatch.json  
Slower (14):
- pickle_dict: 91.1 us +- 2.2 us -> 98.0 us +- 3.3 us: 1.08x slower (+8%)
- xml_etree_parse: 534 ms +- 29 ms -> 565 ms +- 27 ms: 1.06x slower (+6%)
- crypto_pyaes: 679 ms +- 22 ms -> 708 ms +- 22 ms: 1.04x slower (+4%)
- regex_effbot: 12.1 ms +- 0.2 ms -> 12.6 ms +- 0.2 ms: 1.04x slower (+4%)
- tornado_http: 678 ms +- 21 ms -> 704 ms +- 31 ms: 1.04x slower (+4%)
- pidigits: 432 ms +- 7 ms -> 447 ms +- 18 ms: 1.03x slower (+3%)
- spectral_norm: 869 ms +- 21 ms -> 898 ms +- 22 ms: 1.03x slower (+3%)
- unpickle_list: 20.6 us +- 0.6 us -> 21.2 us +- 0.8 us: 1.03x slower (+3%)
- pathlib: 87.9 ms +- 3.0 ms -> 90.6 ms +- 3.5 ms: 1.03x slower (+3%)
- pickle_list: 13.0 us +- 0.3 us -> 13.3 us +- 0.4 us: 1.03x slower (+3%)
- meteor_contest: 367 ms +- 13 ms -> 378 ms +- 14 ms: 1.03x slower (+3%)
- scimark_sor: 991 ms +- 28 ms -> 1.02 sec +- 0.03 sec: 1.03x slower (+3%)
- sympy_expand: 1.73 sec +- 0.05 sec -> 1.77 sec +- 0.04 sec: 1.02x slower (+2%)
- python_startup: 29.5 ms +- 1.1 ms -> 30.1 ms +- 1.9 ms: 1.02x slower (+2%)

Faster (8):
- sympy_integrate: 84.3 ms +- 8.3 ms -> 78.3 ms +- 5.0 ms: 1.08x faster (-7%)
- call_simple: 30.6 ms +- 1.7 ms -> 29.0 ms +- 1.4 ms: 1.06x faster (-5%)
- pickle: 43.2 us +- 3.2 us -> 41.1 us +- 1.9 us: 1.05x faster (-5%)
- call_method_unknown: 36.4 ms +- 1.6 ms -> 35.0 ms +- 1.5 ms: 1.04x faster (-4%)
- scimark_lu: 781 ms +- 42 ms -> 752 ms +- 34 ms: 1.04x faster (-4%)
- sympy_sum: 385 ms +- 21 ms -> 372 ms +- 17 ms: 1.03x faster (-3%)
- logging_silent: 1.30 us +- 0.04 us -> 1.26 us +- 0.04 us: 1.03x faster (-3%)
- django_template: 665 ms +- 20 ms -> 643 ms +- 18 ms: 1.03x faster (-3%)

Benchmark hidden because not significant (42)

[1]: https://github.com/lulouie/cpython/blob/compact_empty_dict/Objects/dictobject.c#L1247