Convert BpfMap native methods to use @FastNative to reduce JNI overhead.
Refactor synchronizeKernelRCU() to be @CriticalNative for maximum
performance by changing its error handling to return an error code
instead of throwing directly from native code.
(In practice we don't expect it to *ever* fail)
FYI:
@FastNative and @CriticalNative are Android-specific annotations
that signal to the ART runtime to use a lower-overhead JNI transition,
resulting in better performance.
A standard JNI call tells the Garbage Collector (GC) that the thread
is transitioning to a 'Native' state. This is a signal to the GC that
the thread might be busy for a while and shouldn't be suspended arbitrarily.
@FastNative is for short, quick functions:
This provides a moderately faster JNI call (thread is still 'Runnable').
The native function signature remains the same as a standard JNI method,
and it can still access the JNIEnv* to interact with Java objects
or throw exceptions.
@CriticalNative is for short, quick & trivial functions:
This provides the fastest possible JNI transition and is intended
for simple, performance-critical leaf functions.
It comes with strict requirements:
- The native method cannot throw exceptions, create Java objects,
or make any other JNI calls.
- All arguments and the return type must be primitive, ie:
jboolean [bool]
jbyte [s8]
jchar [u16]
jshort [s16]
jint [s32]
jlong [s64]
jfloat [32-bit]
jdouble [64-bit]
void
Java objects like String or byte[] are not allowed.
Because of these restrictions, the native C++ function signature
must not include JNIEnv* or jobject/jclass parameters.
(This likely also means it must be 'static')
Test: TreeHugger
Flag: EXEMPT mainline
Signed-off-by: Maciej Żenczykowski <maze@google.com>
Change-Id: I9b6107b26086df2e87218ff9274593e9f2eb6b0b
2afef5070a