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Statically cache the String value of g_internal_field for a small performance gain #4863

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merged 5 commits into from
Sep 9, 2022
Merged

Statically cache the String value of g_internal_field for a small performance gain #4863

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0b6099f
Statically cache the String value of g_internal_field for a small per…
Sep 5, 2022
3f95483
Fix lint
Sep 9, 2022
2d9ed2e
Update src/jsi/jsi_class.hpp
Sep 9, 2022
c256c31
Update src/jsi/jsi_class.hpp
Sep 9, 2022
1ed1d1e
Change to empty string for internal field name
Sep 9, 2022
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1 change: 1 addition & 0 deletions CHANGELOG.md
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Original file line number Diff line number Diff line change
@@ -1,6 +1,7 @@
## vNext (TBD)

### Enhancements
* Small improvement to performance by caching JSI property String object [#4863](https://github.com/realm/realm-js/pull/4863)
* None.

### Fixed
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20 changes: 16 additions & 4 deletions src/jsi/jsi_class.hpp
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Expand Up @@ -145,7 +145,10 @@ inline void copyProperty(JsiEnv env, const fbjsi::Object& from, const fbjsi::Obj
defineProperty(env, to, name, *prop);
}

inline constexpr const char g_internal_field[] = "__Realm_internal";
// The name used for the property on the JS object which stores the reference to the corresponding C++ object.
// We use an empty string as testing showed it was 1% faster with JSC and 4% faster with Hermes than using
// an actual string, and also has the benefit that it is not a valid Realm object key name.
inline constexpr const char g_internal_field[] = "";

template <typename T>
using ClassDefinition = js::ClassDefinition<js::realmjsi::Types, T>;
Expand Down Expand Up @@ -240,6 +243,10 @@ class ObjectWrap {
// Also, may need to suppress destruction.
inline static std::optional<JsiFunc> s_ctor;

// Cache the JSI String instance representing the field name of the internal
// C++ object for the lifetime of the current env, as this is a hot path
inline static std::optional<fbjsi::String> s_js_internal_field_name;

/**
* @brief callback for invalid access to index setters
* Throws an error when a users attemps to write to an index on a type that
Expand Down Expand Up @@ -310,9 +317,10 @@ class ObjectWrap {
.asFunction(env));

js::Context<js::realmjsi::Types>::register_invalidator([] {
// Ensure the static constructor is destructed when the runtime goes away.
// This is to avoid the reassignment of s_ctor throwing because the runtime has disappeared.
// Ensure the static constructor and JSI String reference are destructed when the runtime goes away.
// This is to avoid reassignment and destruction throwing because the runtime has disappeared.
s_ctor.reset();
s_js_internal_field_name.reset();
});

for (auto&& [name, prop] : s_type.static_properties) {
Expand Down Expand Up @@ -490,7 +498,11 @@ class ObjectWrap {

static Internal* get_internal(JsiEnv env, const JsiObj& object)
{
auto internal = object->getProperty(env, g_internal_field);
if (REALM_UNLIKELY(!s_js_internal_field_name)) {
s_js_internal_field_name = fbjsi::String::createFromAscii(env, g_internal_field);
}

auto internal = object->getProperty(env, *s_js_internal_field_name);
if (internal.isUndefined()) {
// In the case of a user opening a Realm with a class-based model,
// the user defined constructor will get called before the "internal" property has been set.
Expand Down