Valhalla, startup, performance of interpreter, and vwithfield

[Sergey Kuksenko]

Hi All,

I did quick evaluation of startup and interpreter performance cost. I 
have to take back my words that "vwithfield is major contributor to the 
interpreter speed and merged(or fused) vwithfield could improve 
interpreter performance". It was quite long time age when I was looking 
into interpreter's performance last time. I have to say that a huge work 
was done for interpreter since that time and now I don't consider 
interpreter's performance as an issue. As for vwithfield, now cost of 
the single vwithfield (in the interpreter) is approximately 200ns (on 
2.2GHz freq). It is not a big nor a small value. If compare cost of 
value creation vs cost similar classic java object creation (simple 
writes) then single vwithfield costs ~7%-10% from the whole object 
creation. So I am guessing that if you have a value with 10 fields (and 
10 vwithfield operations) - you may double value creation cost, but it 
will have minor impact for the whole execution.

Also I have to say that if look into startup for the first execution of 
code - interpreter takes less than 1%. All others actions (classloading, 
verification, etc..) take much more time. As for "time to performance" - 
I didn't evaluate it yet. Interpreter's impact could be higher in that 
case. At the same moment  - working TieredCompilation will improve "time 
to performance" much more than any interpreter tuning.