But using all these tricks just throws away reason you've moved to Java. Following this further, you can write faster code in C when using only ASM insets.
The next thing - almost every example of C vs. Java speed comparisons was created by weak C programmers. The code was poor and not optimized.
I hate titles "Framework A is doing this, why framework B isn't doing this?"
Use what seems best to You. Rails always tend to have faster movement with Ruby support, but to be honest having at least 1 year is enough to redeploy app with new Rails & Ruby. If not then you're doing it wrong.
The next thing - almost every example of C vs. Java speed comparisons was created by weak C programmers. The code was poor and not optimized.