On Fri, Aug 19, 2022 at 02:17:32PM -0400, Joel Fernandes wrote: > On Fri, Aug 19, 2022 at 2:14 PM Joel Fernandes <joel@xxxxxxxxxxxxxxxxx> wrote: > [..] > > >> Things are much better with the following change. However, this brings > > >> me to a question about lock-contention based or any deferring and boot time. > > >> > > >> If you have a path like selinux doing a synchronize_rcu(), shouldn't we > > >> skip the jiffie waiting for the bypass timer? Otherwise things > > >> synchronously waiting will slow down more than usual. Maybe bypassing > > >> should not be done for any case until boot up is done. I'm curious to > > >> see if that improves boot time. > > > > > > Why not simply disable laziness at boot time and enable it only after > > > booting is complete? The exiting rcupdate.rcu_normal_after_boot kernel > > > boot parameter uses a similar scheme. > > > > That sounds like the right thing to good, but unfortunately it wont help > > this problem. The boot time issue happens after init has started. So the > > OS is still "booting" even though the kernel has. > > > > Also the problem can happen after boot as well, like if RCU > > lazy/non-lazy callbacks come back to back quickly, or so. > > > > But yes nonetheless, I can see the value of disabling it till the > > in-kernel boot completets. > > My mail client is acting weird. I meant to add to this, I wonder if > there is a way other subsystems detect when userspace boots using some > heuristic? I don't know of one, but I bet that ChromeOS has ways. If nothing else, might you add a sysfs write to one of the boot-up phases? Thanx, Paul
