Why is Clojure so slow?

What I would like to see is a `defconstant` macro, which introduces a constant that can not be changed anymore without restarting the JVM.

(def x 1) ; x = 1 (def x 2) ; x = 2 now

(defconstant y 1) ; y = 1 (defconstant y 2) ; Exception

Also a way of fixing functions would be good, so that no lookup is required. Calling such a fixed function has no overhead, it would be a direct call.

If Clojure could dump the Lisp image like SBCL's save-lisp-and-die function, the startup time would be greatly reduced. I wonder if JVM itself can dump its current state and then restore execution.

Another approach to the problem would be similar to FastCGI: keep one Clojure server process running and execute scripts on it.

> If Clojure could dump the Lisp image like SBCL's save-lisp-and-die function, the startup time would be greatly reduced. I wonder if JVM itself can dump its current state and then restore execution.

It's still hard to understand why aren't Oracle working on something like that. It's not as if they don't care about desktop at all -- JavaFX is going to be part of Java8 and they are even working on a new packaging tool-chain for it. JVM's start-up time and inability to allocate memory when needed (as compared to up-front way it's done now) are the major reasons why Java/JVM is (still) a bad solution for desktop and cli applications.

Don't compare Clojure to C, comparing it to Python or Ruby makes more sense because they're all high-level dynamic languages. Sure Clojure runs on the compiling JVM but that doesn't put it into another category; you can also JIT compile Python in a few ways.

If we can make working websites and even games in Python, we can make them in Clojure too. What kills Clojure for small scripts and not-long-running applications is the startup time and that can mostly be attributed to JVM. Also, the memory footprint of a JVM process tends to grow a lot over time.

I see Clojure rising above specific platforms, though. JVM is in a slow death spiral. CLR might have some traction on Windows. If Python got it platform resettled on something more sophisticated than CPython, that might be a good ecosystem for Clojure.

Vars already default static, so we just need to take better advantage of that in the compiler.