After upgraed from jdk8 to jdk21, we gain ~16% performance improvements, here are some possible valid enhancement.
Reduce JNI Access: ~2x faster
In RandomAccessFile, writeLong requires 8 JNI calls
public final void writeLong(long v) throws IOException {
write((int)(v >>> 56) & 0xFF);
write((int)(v >>> 48) & 0xFF);
write((int)(v >>> 40) & 0xFF);
write((int)(v >>> 32) & 0xFF);
write((int)(v >>> 24) & 0xFF);
write((int)(v >>> 16) & 0xFF);
write((int)(v >>> 8) & 0xFF);
write((int)(v >>> 0) & 0xFF);
}
by converting long into byte array, we can only invoke JNI once
public final void writeLong(long v) throws IOException {
Bits.putLong(buffer, 0, v);
write(buffer, 0, Long.BYTES);
}
Constant Folding: ~12%
@Stable tells compiler this field will be updated at most once, Record compiler jvm its fields is trusted.
Both make compiler do constant folding
SIMD: ~2X
String::hashCode using ArraysSupport.verctorizedHashCode