On Fri, 7 Jul 2023 23:42:51 GMT, 温绍锦 <d...@openjdk.org> wrote: >> src/java.base/share/classes/java/util/UUID.java line 475: >> >>> 473: long msb = mostSigBits; >>> 474: byte[] buf = new byte[36]; >>> 475: UNSAFE.putLongUnaligned( >> >> I understood that since UUID was not used during startup, that using >> VarHandles is the preferred abstraction. > > Using VarHandle will be 10% slower than using Unsafe directly, I haven't > found the reason yet
I believe it’s because `VarHandle`s do bounds checking: https://github.com/openjdk/jdk/blob/581f90e242b8a943215a223189d171b7ede37785/src/java.base/share/classes/java/lang/invoke/X-VarHandleByteArrayView.java.template#L113-L116 https://github.com/openjdk/jdk/blob/581f90e242b8a943215a223189d171b7ede37785/src/java.base/share/classes/java/lang/invoke/X-VarHandleByteArrayView.java.template#L144-L161 ------------- PR Review Comment: https://git.openjdk.org/jdk/pull/14745#discussion_r1257510755
