gh-131955: Allow to disable internal string key caching for json.loads()

[nineteendo]

Benchmark:

script

#mysys.py
import sys

def _getsizeof(obj, seen=None):
    if (obj_id := id(obj)) in seen:
        return 0
    size = sys.getsizeof(obj)
    seen.add(obj_id)
    if isinstance(obj, dict):
        size += sum([_getsizeof(k, seen) + _getsizeof(v, seen) for k, v in obj.items()])
    elif isinstance(obj, list):
        size += sum(_getsizeof(v, seen) for v in obj)
    return size

def getsizeof(obj):
    size = _getsizeof(obj, set())
    for unit in ['B', 'KB', 'MB', 'GB', 'TB']:
        if size < 1024:
            break
        size /= 1024
    return f"{size:.2f} {unit}"

::json_cache_keys.bat
@echo off
echo 100 repeated keys
call main\python            -m timeit -s "import json; s = json.dumps([{'abc': 0}] * 100)" "json.loads(s)"
call json_cache_keys\python -m timeit -s "import json; s = json.dumps([{'abc': 0}] * 100)" "json.loads(s, cache_keys=False)"
echo 10,000 repeated keys
call main\python            -m timeit -s "import json; s = json.dumps([{'abc': 0}] * 10_000)" "json.loads(s)"
call json_cache_keys\python -m timeit -s "import json; s = json.dumps([{'abc': 0}] * 10_000)" "json.loads(s, cache_keys=False)"
echo 1,000,000 repeated keys
call main\python            -m timeit -s "import json; s = json.dumps([{'abc': 0}] * 1_000_000)" "json.loads(s)"
call json_cache_keys\python -m timeit -s "import json; s = json.dumps([{'abc': 0}] * 1_000_000)" "json.loads(s, cache_keys=False)"

echo 100 different keys
call main\python            -m timeit -s "import json; s = json.dumps([{str(i): 0} for i in range(100)])" "json.loads(s)"
call json_cache_keys\python -m timeit -s "import json; s = json.dumps([{str(i): 0} for i in range(100)])" "json.loads(s, cache_keys=False)"
echo 10,000 different keys
call main\python            -m timeit -s "import json; s = json.dumps([{str(i): 0} for i in range(10_000)])" "json.loads(s)"
call json_cache_keys\python -m timeit -s "import json; s = json.dumps([{str(i): 0} for i in range(10_000)])" "json.loads(s, cache_keys=False)"
echo 1,000,000 different keys
call main\python            -m timeit -s "import json; s = json.dumps([{str(i): 0} for i in range(1_000_000)])" "json.loads(s)"
call json_cache_keys\python -m timeit -s "import json; s = json.dumps([{str(i): 0} for i in range(1_000_000)])" "json.loads(s, cache_keys=False)"

echo ### memory ###

echo 100 repeated keys
call main\python            -c "import json, mysys; print(mysys.getsizeof(json.loads(json.dumps([{'abc': 0}] * 100))))"
call json_cache_keys\python -c "import json, mysys; print(mysys.getsizeof(json.loads(json.dumps([{'abc': 0}] * 100), cache_keys=False)))"
echo 10,000 repeated keys
call main\python            -c "import json, mysys; print(mysys.getsizeof(json.loads(json.dumps([{'abc': 0}] * 10_000))))"
call json_cache_keys\python -c "import json, mysys; print(mysys.getsizeof(json.loads(json.dumps([{'abc': 0}] * 10_000), cache_keys=False)))"
echo 1,000,000 repeated keys
call main\python            -c "import json, mysys; print(mysys.getsizeof(json.loads(json.dumps([{'abc': 0}] * 1_000_000))))"
call json_cache_keys\python -c "import json, mysys; print(mysys.getsizeof(json.loads(json.dumps([{'abc': 0}] * 1_000_000), cache_keys=False)))"

100 repeated keys
10000 loops, best of 5: 25.5 usec per loop # before
10000 loops, best of 5: 26.3 usec per loop # after
# -> 1.03x faster (no difference)
10,000 repeated keys
100 loops, best of 5: 2.56 msec per loop # before
100 loops, best of 5: 2.3 msec per loop # after
# -> 1.11x faster
1,000,000 repeated keys
1 loop, best of 5: 359 msec per loop # before
1 loop, best of 5: 385 msec per loop # after
# -> 1.07x SLOWER

100 different keys
10000 loops, best of 5: 27.8 usec per loop # before
10000 loops, best of 5: 26.4 usec per loop # after
# -> 1.05x faster
10,000 different keys
100 loops, best of 5: 2.93 msec per loop # before
100 loops, best of 5: 2.33 msec per loop # after
# -> 1.26x faster
1,000,000 different keys
1 loop, best of 5: 676 msec per loop # before
1 loop, best of 5: 392 msec per loop # after
# -> 1.72x faster

### memory ###

100 repeated keys
18.94 KB # before
23.19 KB # after
# -> 1.22x more memory
10,000 repeated keys
1.84 MB # before
2.26 MB # after
# -> 1.23x more memory
1,000,000 repeated keys
183.53 MB # before
225.50 MB # after
# -> 1.23x more memory

• Issue: Allow to disable internal string key caching for json.loads() #131955

[ghost]

All commit authors signed the Contributor License Agreement.

[nineteendo]

It seems like there are no tests to check if new parameters aren't passed.