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? Thanks, - Joel
