Anyone claiming something like this obviously hasn’t dig into GCs. You honestly think that writing into memory at each access, especially atomically is anywhere near the performance of a GC that can do most of its work in parallel and just flip a bit to basically “having deleted” everything no longer accessible?
Tracing is batched up in GC pauses, rather than on every access as with naive RC. It is necessary to stop the world, but the work done in the pause does not need to use atomic operations.
Atomics are handy in a parallel/multi-core tracing collector, but IME pointer chasing in tracing somehow manages to cover the time it takes to do atomic operations.
The goal was to write a network driver in several languages. Nobody said anything about comparing memory management techniques, nor would the Swift implementation use a stack allocator anyways.
Swift’s value types have reference counts because they may have members that need their lifetimes to be managed appropriately. (For example, if they’re reference types.)
This is incorrect, value types are not referenced counted in Swift. If a value type contains a reference type member (usually an anti pattern!), then that member’s reference count is indeed incremented when the value type is copied. But it is not accurate to claim that value types themselves have reference counts.
Yes, fair enough. I was thinking of this more from the perspective of types that have internal reference types that are opaque so it’s effectively like the value type itself having a reference count on it, but yes, really it’s the internal storage that is getting the count.
This isn't the kind of program Swift was designed to perform well for.
Nor is wallclock speed even what the system should be optimizing for, since you buy phones to run apps not to run the system. You should be measuring how well it gets out of the way of the important work.
"From its earliest conception, Swift was built to be fast. Using the incredibly high-performance LLVM compiler technology, Swift code is transformed into optimized machine code that gets the most out of modern hardware. The syntax and standard library have also been tuned to make the most obvious way to write your code also perform the best whether it runs in the watch on your wrist or across a cluster of servers.
Swift is a successor to both the C and Objective-C"