Still no, because STW GC can pause innocent code in arbitrary unexpected moments.
If you’re pausing the thread because the thread is doing some work eg calling into system to do I/O, this is not considered a pause (even though technically it is, as the thread may be simply paused and waiting for data) but rather just the cost of the operation. If the thread is being interrupted and paused because some unrelated operation has to run - now that’s bad and considered a true pause.
> Still no, because STW GC can pause innocent code in arbitrary unexpected moments.
Well, yes, that's the problem, isn't it? And that's the point I was making. Pauses in the main thread absolutely count for latency purposes. Note that in most stop-the-world GCs you also can have pretty good control over when the GC is invoked, and that doesn't make things better.
The idea that you can always predict when cascading deletes happen in RAII code is also misleading. They can easily be hidden behind an abstraction barrier. Do you exactly know what's happening under the hood in all third-party libraries that you use, just for an example?
> If you’re pausing the thread because the thread is doing some work eg calling into system to do I/O, this is not considered a pause
In real-time scenarios (soft or hard), it absolutely is. "Regular" operations are absolutely part of your latency budget, and if "regular" operations can exceed it, you absolutely have a problem. See e.g. pretty much any of Gil Tene's talks on the subject.
The kernel (as long as it's not realtime) also pauses innocent code in arbitrary, unexpected moments, and modern concurrent collectors like ZGC pause such "innocent" code for no longer than the OS does. These synchronisation pauses are of roughly constant duration (regardless of working set/heap size) and overall introduce unexpected latency to a lesser degree than the freeing work done by refcounting collections.
