On Thu, Jul 14, 2016 at 08:43:51PM +0200, Oleg Nesterov wrote: > On 07/14, Peter Zijlstra wrote: > > > > The current percpu-rwsem read side is entirely free of serializing > > instructions at the cost of having a synchronize_sched() in the write > > path. > > > > The latency of the synchronize_sched() is too high for some users > > (cgroups), so provide a __percpu_init_rwsem(.bias) argument to forgot > > this synchronize_sched() at the cost of forcing all readers into the > > slow path, which has serializing instructions. > > Oh well... I personally do not think this is what we want... Can't > we just add the stupid rcu_sync_enter() into cgroup_init() at least > for now?
> Yes, this means the unnecessary .sync() at boot time, but > it will go away after cleanups I am going to send. Those would have to hit the same merge window though; some people (like Arjan) really care about boot times and hunt and kill people adding pointless delays.. > Because, again, we will probably want to change this bias dynamically. Hmm, how so?
