* Benjamin Herrenschmidt <benh@xxxxxxxxxxxxxxxxxxx> wrote: > On Thu, 2011-06-16 at 22:25 +0200, Ingo Molnar wrote: > > > > Whatever does the boosting will need to have process context > > > and can be subject to delays, so that pretty much needs to be a > > > kthread. But it will context-switch quite rarely, so should not > > > be a problem. > > > > So user-return notifiers ought to be the ideal platform for that, > > right? We don't even have to touch the scheduler: anything that > > schedules will eventually return to user-space, at which point > > the RCU GC magic can run. > > > > And user-return-notifiers can be triggered from IRQs as well. > > > > That allows us to get rid of softirqs altogether and maybe even > > speed the whole thing up and allow it to be isolated better. > > I'm a little worried of relying on things returning to userspace. > > One could imagine something like a router appliance where userspace > is essentially asleep forever and everything happens in the kernel > (networking via softirq, maybe NFS kernel server, ...) There's a crazy solution for that: the idle thread could process RCU callbacks carefully, as if it was running user-space code. /me runs Ok, joke aside: this is simply a special case where the idle thread generates RCU work via hardirqs. The idle thread is arguably special and could be handled in a special way: a helper thread that executes only in this case? Thanks, Ingo -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxxx For more info on Linux MM, see: http://www.linux-mm.org/ . Fight unfair telecom internet charges in Canada: sign http://stopthemeter.ca/ Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>