* Mathieu Desnoyers <mathieu.desnoyers@xxxxxxxxxxxx> wrote: > I'm worried about "self-recursion" behaviors that could be > triggered though: if the userland callback code called from a page > fault triggers a page fault all by itself, then it looks like a > good way to bring the system to its knees. [...] Not really, SIGIO isnt being reprocessed until the signal handler returns. > [...] The same apply to context switches. Do you have a way to > handle this in mind ? Shouldnt be a problem in theory: yes, in case of repeat migrations repeat signals will be sent, but they should not nest in any nasty fashion. That's the theory, it needs checking! :-) One furthr optimization would be possible: in case you think we can write the signal handler in assembly or build it with gcc flags that does not use SSE we might also add a 'lightweight signal handler' kind of flag to the kernel, which does not save FPU/vector-CPU(SSE) state. In this case signals become *really* fast on x86, almost as fast as interrupts. One detail: you'd not want to use a queueing signal, because the siginfo queue might overflow. It's also unnecessary: RCU only needs the last migration event, previous history is uninteresting. Thanks, Ingo -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
