3 ms·

I'm curious, in what areas is Java 100x faster than C#?

_pmf_ 10y ago
Aggressive inlining and devirtualization is one thing. Escape analysis that allows objects that one would expect by all rational and technological reason to be required to be allocated on the heap being allowed to be allocated on the stack.
- zigzigzag 10y ago
  It's not just a handful of optimisations. The entire JVM is performance focused in a way the CLR just isn't. Microsoft historically put their resources into the C# language and the IDE. Sun/Oracle put their efforts into the runtime. For instance, the CLR doesn't do any profile guided or speculative optimisations at all. That's a 20% win for most Java apps and even more still for languages with higher levels of abstraction like Scala. So right there from the start .NET is 20% behind. The CLR doesn't have an interpreter, so, it spends a lot of time JIT compiling code that isn't particularly important. That takes CPU time away from your app, not sure how much of an effect that is but I can imagine it's at least another 10% down. C# asks devs to control de-virtualisation by hand to try and compensate, but the JVM can do a better job automatically. CLR is only now starting to look at tiered compilation and even then only a very basic form compared to Java which has had it since Java 8. But not only is the base infrastructure and approach far more advanced, the JVM's JIT compilers are way ahead of even the new RyuJIT. Not just fancy optimisations like devirt and escape analysis/scalar replacement, but even basic things like profile-guided basic block ordering. JVM can do auto-vectorisation of loops, lock optimisations, it can even replace speculatively profile and replace synchronised blocks with hardware (TSX) transactional memory. The CLR is multiple generations behind where HotSpot is. And the JVM team is extending its lead even further with projects like Graal.
shouldbworking 10y ago
Not a ton of places, but in my case forwarding HTTP requests. Netty is close to 100x faster than regular .NET. Another example is JSON serialization. Jackson/GSON are maybe 30x faster than the built-in JSON handling in C#. Everyone smart uses Newtonsoft now, but it was a huge bottleneck until a few years ago. .NET seems to have a lot of rough edges where MS said "fuck it, nobody will complain if this is slow". If you happen to use one of those features that didn't get enough love you get burned. Java is generally polished throughout, most likely due to the sheer volume of software written for the JVM
venture_lol 10y ago
It is faster practically everywhere from 2x and on...

_pmf_ 10y ago

Aggressive inlining and devirtualization is one thing. Escape analysis that allows objects that one would expect by all rational and technological reason to be required to be allocated on the heap being allowed to be allocated on the stack.

zigzigzag 10y ago
It's not just a handful of optimisations. The entire JVM is performance focused in a way the CLR just isn't. Microsoft historically put their resources into the C# language and the IDE. Sun/Oracle put their efforts into the runtime. For instance, the CLR doesn't do any profile guided or speculative optimisations at all. That's a 20% win for most Java apps and even more still for languages with higher levels of abstraction like Scala. So right there from the start .NET is 20% behind. The CLR doesn't have an interpreter, so, it spends a lot of time JIT compiling code that isn't particularly important. That takes CPU time away from your app, not sure how much of an effect that is but I can imagine it's at least another 10% down. C# asks devs to control de-virtualisation by hand to try and compensate, but the JVM can do a better job automatically. CLR is only now starting to look at tiered compilation and even then only a very basic form compared to Java which has had it since Java 8. But not only is the base infrastructure and approach far more advanced, the JVM's JIT compilers are way ahead of even the new RyuJIT. Not just fancy optimisations like devirt and escape analysis/scalar replacement, but even basic things like profile-guided basic block ordering. JVM can do auto-vectorisation of loops, lock optimisations, it can even replace speculatively profile and replace synchronised blocks with hardware (TSX) transactional memory. The CLR is multiple generations behind where HotSpot is. And the JVM team is extending its lead even further with projects like Graal.

shouldbworking 10y ago

Not a ton of places, but in my case forwarding HTTP requests. Netty is close to 100x faster than regular .NET. Another example is JSON serialization. Jackson/GSON are maybe 30x faster than the built-in JSON handling in C#. Everyone smart uses Newtonsoft now, but it was a huge bottleneck until a few years ago. .NET seems to have a lot of rough edges where MS said "fuck it, nobody will complain if this is slow". If you happen to use one of those features that didn't get enough love you get burned. Java is generally polished throughout, most likely due to the sheer volume of software written for the JVM

venture_lol 10y ago

It is faster practically everywhere from 2x and on...