Messages in this thread | | | Date | Mon, 14 Sep 2015 14:41:05 -0700 | From | Davidlohr Bueso <> | Subject | Re: [PATCH v6 4/6] locking/pvqspinlock: Collect slowpath lock statistics |
| |
On Mon, 14 Sep 2015, Waiman Long wrote:
>You can't use debugfs if we want to have per-cpu stats. We will have >to use sysfs instead. This will require more code changes. It is >certainly doable, but we have to choose between simplicity and >performance overhead. Right now, I am assuming that lock PV lockstat >is used primarily for debugging purpose and won't be enabled on >production system. If we want to have this capability in production >systems, we will certainly need to change it to per-cpu stats and use >sysfs instead. > >The original PV ticketlock code used debugfs and I was just following >its footstep. Do you think it is worthwhile to have this capability >available on production system by default?
If we can prove that the overhead is small enough, and do it correctly (ie see how we do vmstats), it would be _very_ useful data to have enabled by default for debugging performance issues; methinks. But right now we have nowhere near that kind of data, not even with this atomic variant -- although I recall you did mention a workload in a previous iteration (which would be good to have in the changelog).
| |