perf(android): faster JNI bridge and bounded wrapper memory for the napi and jsi runtimes - #75
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Node-API tree only. Measured on x86_64 emulator against this base; the
runtime test suite passes at parity on V8, QuickJS, Hermes and JSC.
- Object lifecycle: wrappers for Java-returned objects are held weakly
(JS-constructed instances stay strong so Java can call back into them),
each wrapper reports external memory so the engine collects under native
pressure, the wrapper finalizer releases the Java side itself, and the
id->ref map entries are released from the looper post-finalizers instead
of waiting for a Java-GC notification. Fixes unbounded growth (LMK kill
after ~200k returned objects).
- No host-object proxy for plain instances (arrays keep it for indexed
access); a live proxy for JS-constructed instances is still returned.
- Wrapper creation: plain object with a cached class prototype instead of
instantiating the JSObject class per wrapper; single napi_wrap attachment.
- Return-type cache on MetadataEntry: declared return class resolved once
per call site; skips the per-object Class.getName() up-call.
- this resolution: weak-ref cache seeded at link time, no IsSameObject probe
per hit; V8 resolves plain wrappers with napi_unwrap ahead of the #napi
marker probe (V8 only: the QuickJS/JSC shims treat any object opaque as
the wrap payload).
- Strings stay UTF-16 in both directions; removes a double re-encode, a
heap-buffer leak on every string argument and non-BMP mangling.
- Metadata-first overload match is skipped once a single-candidate call
site is bound (it re-ran a signature parse, napi_typeof and IsInstanceOf
on every call).
- js_get_array_doubles: bulk array read (V8: v8::Array::Iterate) for
double[]/int[] arguments; generic napi_get_element loop elsewhere.
- JNIEnv cached per thread; NewLocalRef skips a redundant ExceptionCheck.
- JSC shim: JSString::CopyTo copied size bytes instead of size JSChars,
so napi_get_value_string_utf16 returned garbage.
Java call cost, base -> patched (us/call):
V8 add 0.310 -> 0.139, concat 1.77 -> 0.81, sum array 1.96 -> 1.25,
object return 11.4 -> 5.4
QuickJS add 0.366 -> 0.207, object return 7.1 -> 5.2
Hermes add 0.568 -> 0.376, object return 47.1 -> 9.4
…gine tree Brings the jsi binding layer in line with the napi tree (previous commit) so both share the same object model and bridge behaviour: - Wrappers for Java-returned objects are held weakly (WrapperHandle), the native-state destructor posts the Java-side release to the looper, and each wrapper is accounted through EngineHost::AdjustExternalMemory. JS-constructed instances keep their strong handle. - No host-object proxy for plain instances; a live proxy for JS-constructed instances is still returned for identity. - Plain-object wrappers with a per-class cached prototype. - Return-type cache on MetadataEntry for monomorphic object returns. - Weak-ref id cache seeded at link time, no IsSameObject probe per hit. - Strings stay UTF-16 in both directions. New engine API String::createFromUtf16 / utf16Length / copyUtf16: native on V8 and JSC, transcoded through jsi/shared/Utf16.h on QuickJS and Hermes. Also fixes non-BMP text being mangled through NewStringUTF. - New engine API Array::copyNumbers for double[]/int[] arguments (V8: v8::Array::Iterate; generic loop elsewhere). - JNIEnv cached per thread. Measured on x86_64 emulator against the same base the jsi tree was already at or ahead of the patched napi tree, so the timing effect here is within noise except QuickJS object returns (4.34 -> 3.68 us). The runtime test suite passes at parity on V8, QuickJS, Hermes and JSC (431 specs each).
WalkthroughThe change adds UTF-16 and bulk numeric conversion support across JavaScript engines, caches JNI environments per thread, and refactors JavaScript wrapper creation, ownership, metadata resolution, and finalization in both JSI and N-API paths. ChangesBridge and wrapper runtime
Priority: ➖ Normal Estimated code review effort: 5 (Critical) | ~90 minutes Change: Bug fix Sequence Diagram(s)sequenceDiagram
participant JavaCall
participant CallbackHandler
participant ObjectManager
participant JavaScriptRuntime
JavaCall->>CallbackHandler: return Java object
CallbackHandler->>ObjectManager: resolve metadata and create wrapper
ObjectManager->>JavaScriptRuntime: create object and set prototype
JavaScriptRuntime-->>ObjectManager: finalize wrapper later
ObjectManager-->>JavaCall: manage Java instance reference
Suggested reviewers: Merge Risk: 🟠 High · up to Wrapper teardown and recreation can crash the runtime or invalidate live Java-backed objects, while some strings and array conversions can produce incorrect results. These issues should be fixed before merge. 🚥 Pre-merge checks | ✅ 4 | ❌ 1❌ Failed checks (1 warning)
✅ Passed checks (4 passed)
✨ Finishing Touches🧪 Generate unit tests (beta)
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Actionable comments posted: 8
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Inline comments:
In `@NativeScript/ffi/jni/jsi/jni/JEnv.cpp`:
- Line 581: Update JEnv::NewLocalRef() to store the result of
m_env->NewLocalRef(ref), check and propagate any pending JNI exception, and
preserve the null result when no exception is pending so
TryGetJavaThrowableObject() can handle it correctly.
In `@NativeScript/ffi/jni/jsi/jni/LRUCache.h`:
- Around line 103-105: Update both cache implementations so seed returns whether
insertion occurred, preserving the existing insert behavior for new keys. In
both ObjectManager::Link implementations, use that status to call
DeleteWeakGlobalRef for the supplied weak reference when seed rejects a
duplicate key, ensuring duplicate links are released consistently.
In `@NativeScript/ffi/jni/jsi/objectmanager/ObjectManager.cpp`:
- Around line 725-726: Update the WrapperPostFinalizer scheduling in
ObjectManager to carry an entry-generation or wrapper token alongside
JavaObjectID, and validate it before performing Java cleanup, m_idToObject
erasure, or makeInstanceWeak/cache removal. Ensure replacement wrappers are not
evicted when the deferred callback runs, while keeping the finalized wrapper’s
external-memory decrement unconditional.
- Around line 671-674: Update CreateJSWrapperForNode and the shared Link/helper
flow so every recreated wrapper restores the Java strong reference after Link
uses strongRef=false, including non-array nodes returned directly; do not rely
on GetOrCreateProxy, which only runs for arrays and currently performs this
restoration.
In `@NativeScript/ffi/jni/jsi/objectmanager/ObjectManager.h`:
- Around line 121-123: Replace the raw owner and runtime pointers used by
JSInstanceInfo weak wrappers with teardown-safe shared state, or ensure
OnDisposeRuntime invalidates every live JSInstanceInfo before ObjectManager and
JsRuntime are destroyed. Update Link, JSInstanceInfo::~JSInstanceInfo, and the
runtime teardown path so finalizer posting never dereferences a destroyed
ownerRuntime or ObjectManager.
In `@NativeScript/ffi/jni/napi/jni/JEnv.cpp`:
- Line 581: Update the JEnv method wrapping m_env->NewLocalRef(ref) to call
CheckForJavaException() immediately after creating the local reference,
preserving JNI exception translation before returning the reference.
In `@NativeScript/jsi/shared/Utf16.h`:
- Around line 18-19: Update utf16::toUtf8 and the Hermes/QuickJS
JsString::createFromUtf16 paths to preserve isolated high and low UTF-16
surrogates using each backend’s reversible representation instead of replacing
them with U+FFFD. Keep valid surrogate pairs decoding normally, and add parity
tests covering isolated high and low surrogates through
ArgConverter::convertToJsString.
In `@NativeScript/napi/v8/jsr.cpp`:
- Line 598: Update the v8::Array::Iterate handling in js_get_array_doubles to
track how many entries the callback actually copies, and return failure when
that total differs from count before reporting success. Preserve the existing
numbersOnly and count behavior for complete walks so sparse arrays cannot
produce unwritten output slots.
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Run ID: d52d05fc-57d2-46d1-b754-fc9e306ac1da
📒 Files selected for processing (38)
NativeScript/ffi/jni/jsi/callbackhandlers/CallbackHandlers.cppNativeScript/ffi/jni/jsi/conversion/ArgConverter.cppNativeScript/ffi/jni/jsi/conversion/ArgConverter.hNativeScript/ffi/jni/jsi/conversion/JsArgConverter.cppNativeScript/ffi/jni/jsi/jni/JEnv.cppNativeScript/ffi/jni/jsi/jni/JEnv.hNativeScript/ffi/jni/jsi/jni/LRUCache.hNativeScript/ffi/jni/jsi/metadata/MetadataEntry.hNativeScript/ffi/jni/jsi/metadata/MetadataNode.cppNativeScript/ffi/jni/jsi/metadata/MetadataNode.hNativeScript/ffi/jni/jsi/objectmanager/ObjectManager.cppNativeScript/ffi/jni/jsi/objectmanager/ObjectManager.hNativeScript/ffi/jni/napi/callbackhandlers/CallbackHandlers.cppNativeScript/ffi/jni/napi/conversion/ArgConverter.hNativeScript/ffi/jni/napi/conversion/JsArgConverter.cppNativeScript/ffi/jni/napi/jni/JEnv.cppNativeScript/ffi/jni/napi/jni/JEnv.hNativeScript/ffi/jni/napi/jni/LRUCache.hNativeScript/ffi/jni/napi/metadata/MetadataEntry.hNativeScript/ffi/jni/napi/metadata/MetadataNode.cppNativeScript/ffi/jni/napi/metadata/MetadataNode.hNativeScript/ffi/jni/napi/objectmanager/ObjectManager.cppNativeScript/ffi/jni/napi/objectmanager/ObjectManager.hNativeScript/jsi/hermes/HermesRuntime.hNativeScript/jsi/jsc/JSCRuntime.hNativeScript/jsi/jsc/JSCValue.cppNativeScript/jsi/quickjs/QuickJSRuntime.hNativeScript/jsi/shared/Utf16.hNativeScript/jsi/v8/V8Runtime.hNativeScript/napi/common/jsr_common.hNativeScript/napi/hermes/jsr.cppNativeScript/napi/jsc/jsr.cppNativeScript/napi/primjs/jsr.cppNativeScript/napi/quickjs/jsr.cppNativeScript/napi/v8/jsr.cppNativeScript/runtime/android/jsi/workers/WorkerWrapper.cppNativeScript/runtime/android/napi/workers/WorkerWrapper.cppvendor/jsc/jsc-api.cpp
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…ycle - JEnv::NewLocalRef: restore CheckForJavaException (both trees). - LRUCache::seed: replace an existing entry instead of leaking the caller's fresh weak global ref on wrapper recreate (both trees). - Recreated wrappers left the Java instance weak: Java reuses the id of a weakened instance and only the array/proxy path re-strengthened it. New ObjectManager::EnsureInstanceStrong, called from CreateJSWrapperForNode and GetOrCreateProxy (both trees). - jsi WrapperPostFinalizer: leave the id alone when a new wrapper was linked under it between the GC and the looper drain. - jsi JSInstanceInfo: reach the ObjectManager/runtime through a shared OwnerToken that OnDisposeRuntime clears, so native state the engine destroys after ~Runtime is a no-op. - jsi Hermes/QuickJS: createFromUtf16/utf16Length/copyUtf16 on the engines' own two-byte APIs so unpaired surrogates survive; drop jsi/shared/Utf16.h. - V8 js_get_array_doubles / Array::copyNumbers: fail over to the per-element path when a dictionary-mode array skipped holes. Test suites: napi 503/503 (V8, QuickJS, JSC), 502/502 (Hermes); jsi 431/431 on all four engines.
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Summary
Three commits: bridge and wrapper-lifecycle optimizations for the Node-API runtime, a port of the same object model to the direct-engine (jsi) tree so the two stay at parity, and a follow-up addressing the review findings on both.
Measured on an x86_64 emulator (API 36) with a NativeScript app calling a small Java/Kotlin class in tight loops (
add(int,int),mul(double,double),strlen(String),concat(String,String),sumArray(double[16]), and a method returning aPointobject), 9 samples per case, median reported, µs per call. All four engine test suites pass at parity with the base (9ad80841).Node-API runtime (
b5a9e972)Java call cost, base → this PR:
The JSC baseline never finishes this benchmark on the base (object returns ~100 µs each with unbounded memory); against the published
9.1.0-alpha.0JSC package the patched build is flat on primitives and ~3× faster on object returns.Memory: returning 220k Java objects in one turn previously grew the process to ~1 GB and got it LMK-killed. Native heap now stays at 50–75 MB across repeated runs.
For reference, the patched V8 runtime is now at or ahead of the classic V8 runtime on every case (
add0.246 → 0.127,concat1.01 → 0.72,sum array1.21 → 0.58,make point4.34 → 4.22).What changed
napi_ref; JS-constructed instances (extend/interface implementations) keep the strong ref since Java may call back into them. Each wrapper reports ~1 KB viajs_adjust_external_memoryso the engine schedules GCs under native pressure. The wrapper's finalizer releases the Java side itself (JS-constructed instances that never had a proxy were pinned forever), and theid → refmap entries are released from the looper post-finalizers instead of waiting for a Java-GCnotifyGc.RegisterInstance), it is returned.napi_create_objectwith a per-class cached prototype instead of instantiating theJSObjectclass through a native constructor callback plus an ownconstructorproperty; onenapi_wrapattachment instead of external +#js_infoproperty + wrap.MetadataEntry; the per-objectClass.getName()up-call and string-keyed metadata lookup only run for polymorphic returns.thisresolution. The weak-ref cache is seeded at link time (nogetJavaObjectByIDup-call on first use), the per-hitIsSameObjectprobe is dropped (release paths evict the entry instead), and on V8 plain wrappers resolve throughnapi_unwrapahead of the#napiprototype-chain probe. V8-only because the QuickJS shim'snapi_unwraptreats any object opaque as the wrap payload.napi_get_value_string_utf8twice intonew char[],NewStringUTF(modified UTF-8, mangles non-BMP text) and leaked the buffer on every call; the Java→JS path walked the string three times.charreturns no longer build ajava.lang.String.vector<string>,napi_typeofper arg,GetJavaObjectByJsObject+FindClass+IsInstanceOffor object args). Its result only decides how an unbound entry gets itsjmethodID, so it is skipped once a single-candidate call site is bound. This alone was ~45% of a primitive call.js_get_array_doubles: V8 walks packed arrays withv8::Array::Iterate; other engines get a generic loop. Used fordouble[]/int[]arguments.NewLocalRefskips a redundantExceptionCheck.vendor/jsc/jsc-api.cpp):JSString::CopyTocopiedsizebytes instead ofsize * sizeof(JSChar), sonapi_get_value_string_utf16returned garbage.jsi runtime (
be241ea0)The direct-engine tree did not have the memory or overload-matching problems and was already at or ahead of the patched napi numbers; this commit ports the same object model and bridge behaviour so the two trees match:
Within noise except QuickJS object returns. New engine-layer API:
String::createFromUtf16/utf16Length/copyUtf16(V8NewFromTwoByte/WriteV2, JSCJSStringCreateWithCharacters/GetCharactersPtr, Hermesjsi::String::createFromUtf16/utf16, QuickJS-NGJS_NewStringUTF16/JS_ToCStringLenUTF16) andArray::copyNumbers(V8Array::Iterate, generic elsewhere). The UTF-16 string path also fixes the non-BMP mangling throughNewStringUTF.Review follow-up (
5ba2673a)Addresses the CodeRabbit findings; all confirmed real:
getOrCreateJavaObjectIDconsults the weak table), and only the array/proxy path calledmakeInstanceStrong, so an object returned again after its first wrapper died could be collected by Java under a live wrapper. NewObjectManager::EnsureInstanceStrong(id), called fromCreateJSWrapperForNodeandGetOrCreateProxy.makeInstanceWeak, map erase and cache evict belong to the new wrapper.JSInstanceInfono longer holds rawObjectManager*/JsRuntime*. It shares anOwnerTokenthatOnDisposeRuntimeclears, so native state the engine destroys after~Runtimeis a no-op.LRUCache::seedreplaces an existing entry (evicting the old weak global ref) instead of dropping the caller's fresh one, which leaked a weak global ref per wrapper recreate.JEnv::NewLocalRefgets itsCheckForJavaExceptionback (both trees); only the exception path calls it.jsi/shared/Utf16.hremoved.Array::Iteratepaths count written elements and fall back to per-element conversion when a dictionary-mode array skipped holes.Current build, all bindings (napi / jsi, µs per call)
"C" is a hand-written Node-API addon calling the same Java methods through JNI directly, i.e. the floor for the bridge on each engine.
Verification
test-app, x86_64 debug, CheckJNI on), after the review follow-up: napi 503/503 on V8, QuickJS, JSC and 502/502 on Hermes; jsi 431/431 on all four. Identical to the base on every engine.Notes for reviewers
NativeScript/ffi/jni/{napi,jsi},NativeScript/runtime/android/{napi,jsi}), the per-enginejsr.cppfiles, the fourjsi/*Runtime.hbackends andvendor/jsc/jsc-api.cppare touched.NAPI_VERSION_EXPERIMENTAL, so Node-API finalizers run inside the GC pass (hence the looper post-finalizers for anything that touches handles); and both the V8 and QuickJS shims'napi_unwrapmisread objects with unrelated internal/opaque data, so host-object probes must precede unwrap.concat~5.5 µs is inside the Hermes shim, not the bridge), JSC's 3–6× slower JNI-bound calls (its shim), and going below ~0.1 µs on primitives, which needs V8CFunctionfast calls through the jsi tree.