Except it's a limitation that shows up even if you never make an mmap call. It's just a reality of living with virtual memory (and arguably, with preemptive based kernel scheduling in general as the kernel can decide to context switch from a thread).
> Traditional async I/O engines use direct I/O on locked memory, and if you use async you need to be cognizant of why this is. Half the point of async is to have explicit control and knowledge of when page faults are scheduled. Async is a power tool, not something that should be used lightly for casual tasks nor accidentally pulled in as a dependency.
Cooperative multitasking, to avoid the stalling described in this article, also needs locked memory/explicit control/knowledge of when page faults are scheduled.
> Async is used heavily in some C/C++ domains but it doesn’t seem to cause many issues there, perhaps because dependencies are much more explicit and intentional. Async has also been idiomatic for certain domains in C/C++ for decades so there is an element of maturity around working with it.
It's more that the people in those domains have an understanding of cooperative multitasking's trade-offs, and it is an explicit design choice to employ it.
Modern async models have their origin in addressing serious shortcomings with the traditional POSIX APIs, particularly with respect to mmap and kernel schedulers. You can’t mix the models easily, many parts of POSIX don’t play nicely with async architectures. Traditional async I/O engines use direct I/O on locked memory, and if you use async you need to be cognizant of why this is. Half the point of async is to have explicit control and knowledge of when page faults are scheduled. Async is a power tool, not something that should be used lightly for casual tasks nor accidentally pulled in as a dependency.
The issue here appears to be that it is far too easy for someone to inadvertently mix models, not async per se. Async has substantial advantages versus native kernel threads, so getting rid of async is not a realistic solution. No one is going to give up a several-fold performance increase versus native kernel threads because some developers can’t figure out how to not mix models or the ecosystem doesn’t protect developers against inadvertently mixing models.
Async is used heavily in some C/C++ domains but it doesn’t seem to cause many issues there, perhaps because dependencies are much more explicit and intentional. Async has also been idiomatic for certain domains in C/C++ for decades so there is an element of maturity around working with it.