On 4/7/22 19:27, Kasper Nielsen wrote:
nope, see my previous mail to Ceki, the VM is cheating here if it can
inline the call to MethodHandles.lookup()
Does how the VM cheats really matter? The fact is that the code in the JDK
can
get the calling class and implement something like MethodHandles.lookup() so
it takes ~3 ns. If you implemented something like a lookup class as a normal
user your best bet would be StackWalker.GetCallingClass() and you would end
up with something that is at least 2 magnitudes slower. That is probably not
an issue for most use cases. But for some, it might be a bit of a steep
cost.
/Kasper
Hi Kasper,
sorry to jump in here as an uninvolved onlooker, but I can't resist.
I really don't see why this should matter. Getting the caller class is a
rare edge case that you just do in exceptional situations; most often
it's more for debugging or something.
What users really are interested in is high performance for standard
cases. Implementing a specific optimization into Hotspot to gain few
milliseconds is the least thing I expect from the JVM developers.
I also don't understand why someone should instantiate a logger during
performance critical procedures. In more than 20 years of Java
development, I've never seen the need to create a logger on the fly.
They are *always* assigned to final static variables, or at least to
predefined pools. Everything else would be just wrong: To instantiate a
logger, you have to fetch at least the log level definition from some
configuration source, and this can never be fast. At least not that
we're talking about nanoseconds here.
All logging implementations I know of (and all that make sense) are
highly optimized on log throughput; this can only be achieved by
preprocessing during initialization, why this is slow. But that doesn't
matter, because, as said, you should anyway create logger instances
beforehand.
Sorry for the rant, but I really don't see the use case here.
