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Speed up Object.freeze()
Summary:
Object.freeze() relies on HiddenClass::makeAllReadOnly(), which
iterates through all properties and updates their flags, either creating
a new HiddenClass (HC) for each, or locating the previously created
one. Best case, the performance is
O(number-of-properties)*O(hash-table-lookup).
We can speed this up significantly by caching the transition to the
final HC in the HC where makeAllReadOnly() is invoked. For that we
simply define a new "internal property name" FreezeTransition. The
rest is trivial.
Benchmark:
function make(i) {
return {a: 10, b: 20, c: 30, d: 40, e: 50, f: 60, g: 70, h: 80, i};
}
const N = 1_000_000;
let t1 = Date.now();
for(let i = 0; i < N; ++i)
Object.freeze(make(i));
let t2 = Date.now();
console.log(t2 - t1, "ms");
- Time before: 277 ms
- Time after: 66 ms
Differential Revision: D70845213
