Re: Severe performance regression w/ 4.4+ on Android due to cgroup locking changes

[Peter Zijlstra]

On Thu, Jul 14, 2016 at 04:58:44PM +0200, Oleg Nesterov wrote:
> 
> Of course, this leads to another question: do we really need rcu-sync at
> all, or should we change percpu-rwsem to always work in the "slow" mode
> which is not that slow with your change... I'd like to keep it ;)
> 
> What do you think?

Yes, I think we wants to keep it. There are users where the read size
cost really are performance critical. I still have to repost that lglock
removal series for example, which replaces the fs/locks lglock with a
percpu-rwsem.