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

[John Stultz]

On Wed, Jul 13, 2016 at 11:33 AM, Tejun Heo <tj@xxxxxxxxxx> wrote:
> On Wed, Jul 13, 2016 at 02:21:02PM -0400, Tejun Heo wrote:
>> One interesting thing to try would be replacing it with a regular
>> non-percpu rwsem and see how it behaves.  That should easily tell us
>> whether this is from actual contention or artifacts from percpu_rwsem
>> implementation.
>
> So, something like the following.  Can you please see whether this
> makes any difference?

Yea. So this brings it down for me closer to what we're seeing with
the Dmitry's patch reverting the two problematic commits, usually
10-50us with one early spike at 18ms.

thanks
-john