That made me rather curious how many syscalls a complex GUI application might issue. I wanted to see how many syscalls were happening across my entire system. Thanks to StackOverflow I have a snippet that seems correct[1]:
> perf stat -e raw_syscalls:sys_enter -a -I 1000 sleep 5
Using this, it seems that most programs (as you would probably guess) don't execute a whole lot of syscalls when they're idle. However, starting a complex GUI program definitely causes a pretty massive flurry of syscalls. Starting winecfg without an already-existing wineserver spews a lot of syscalls, somewhere in the neighborhood of 500,000. If we assume that each syscall takes on average around 2µs including the overhead and that they're all serial, I guess that would add up to about 1 second spent on syscalls. That's probably making way too many assumptions, but it does make me feel like it's not completely infeasible to run GUI applications inside of a sandbox like this, though it may very not be compelling when the overhead is factored in.
And of course, just because it could be done does not mean it should, anyway. Even if this is a good idea, I doubt it makes any sense for TinyKVM to be attempting to do it. What TinyKVM does do is already very interesting and probably a lot more practical anyways. It'd probably be better to fork off or build an entire purpose-built sandbox for GUI software, realistically.
Still, pretty interesting stuff to think about.
> And we currently only have very rudimentary support for threads, enough for a server program with ancillary threads to boot up but the expectation is currently that the call into TinyKVM only runs a single thread and we fork multiple copies of the VM to handle requests in parallel.
BTW, I think this design is really cool. This is something I have wanted to exist for a while, even though I don't practically need it.