[Perf] Use compile-time string hashes when dispatching update properties #9841
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vmoroz
reviewed
Apr 21, 2022
| } | ||
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| template <size_t N> | ||
| struct fixed_string { |
vmoroz
reviewed
Apr 21, 2022
| return val[pos]; | ||
| } | ||
| constexpr bool operator==(const char *v) const noexcept { | ||
| return strcmp(val, v) == 0; |
vmoroz
reviewed
Apr 21, 2022
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| } // namespace details | ||
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| #define HASH_STRING(STR) details::fixed_string{STR}.hash() |
There was a problem hiding this comment.
Also, why to create the whole fixed_string here to calculate hash, why not just have a function that does it directly?
vmoroz
reviewed
Apr 21, 2022
| case HASH_STRING("alignItems"): { | ||
| YGAlign align; | ||
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| switch (value_hash) { |
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Description
We currently implement a lot of our update logic and mapping property names to values by using string comparisons.
We can shrink the size on disk and speed things up by instead computing a hash of the property names and comparing the resulting hashes.
What's more, the hashes for the values we compare against, can be computed at compile time.
Type of Change
What
In this PR I am starting with creating the mechanism to do compile-time string hashes, and applying it to one function (
StyleYogaNode). We can then start opting in more and more functions (esp. UpdateProperties and its friends).Results:
✅ Code size for the
StyleYogaNodefunction went down by 16% when I converted the outer comparisons (the property name).✅It went further down when I also converted the property value comparisons, by a total of 47%.
Speed-wise, I ran some micro benchmarkings (with a reduced version of StyleYogaNode) and saw average time per call go from 52 ns to 42 ns, about 20% faster (caveat, the benchmark is a little flimsy so take this number as anecdotal for now...)
Microsoft Reviewers: Open in CodeFlow