Counterpoint: I do a lot of perf work on LibreOffice, which makes extensive use of exceptions, and I have never ever even seen the exception throwing show up on a profile, let alone become a problem.

I think this paper started with a conclusion, and worked backwards to justify it.

I am the the original author, and trust me, I am describing a real world problem. I run massive parallel data processing tasks on machines with 128 cores, and unfortunately some of them produce errors deep within the processing pipeline. From a programming perspective exceptions would be ideal for that scenario, but they cause severe performance problems.

Just think about this: If you have a 100 cores, and 1% of your tasks fail, one core is constantly unwinding. And due to the global lock you quickly get a queue of single threaded unwinding tasks. And things become worse, we expect to have machine with 256 cores soon, and there it is even more dangerous to throw.

If you do not believe me look here: http://wg21.link/p0709 It lists quite a few applications that explicitly forbid exceptions due to performance concerns.

All of this hinges around the global lock, although I'm not sure what you mean exactly. Are you talking about memory allocation, a lock that exception handling takes or something else?

The main problem is the unwinding lock. Memory allocation is a bit unfortunate, too, but much less so.

Note that I am trying to fix the unwinding problem, I have submitted a patch to libunwind to eliminate the contention during unwinding:

https://reviews.llvm.org/D120243

It require application support, unfortunately, as there is currently no way that libunwind can figure out if a shared library has been added or removed. But if you are willing to indicate that from within the application the performance problem is mostly fixed. The memory allocation issue remains, but I can live with that. I cannot live with single threaded unwinding.

Is there a problem if dynamic libraries invoke dlopen/dlclose they also need to call the sync function - correct?

I'm asking because we've developed a Common Lisp implementation that interoperates with C++ and it uses exception handling to unwind the stack (https://github.com/clasp-developers/clasp.git). We hit this global lock in unwinding problem a lot - it causes us a lot of grief.