Memoize the options snapshot#21354
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JukkaL
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May 8, 2026
| write_json_value(buf, cast(JsonValue, values)) | ||
| return {"platform": platform_opt, "other_options": hash_digest(buf.getvalue())} | ||
| cache = manager.options_snapshot_cache | ||
| key = id(cloned) |
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Can you use just cloned as the key?
| buf = WriteBuffer() | ||
| write_json_value(buf, cast(JsonValue, values)) | ||
| cached = (platform_opt, hash_digest(buf.getvalue())) | ||
| cache[key] = cached |
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I think unstructured globs can never be cached, since they are always recreated, so the cache will never be hit (but I'm not 100% sure).
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According to mypy_primer, this change doesn't affect type check results on a corpus of open source code. ✅ |
KevinRK29
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JukkaL
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Jun 12, 2026
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The
options_snapshotis about 6% of CPU on incremental runs in a very large codebase.This caches the
(platform, hash_digest)tuple keyed byid()of the clonedOptions, and keeps each cloned object alive in a parallel_options_snapshot_keepalivelist soid()cannot be reused by the GC after a transient clone is collected.This improved the overall time by roughly 5%, the time taken in the function dropped by ~67% on a warm run, and the ~110k calls dropped to ~220 distinct cloned
Optionswithout any change in output