Re: [RFC PATCH 10/10] psi: aggregate ongoing stall events when somebody reads pressure

[Andrew Morton]

On Thu, 12 Jul 2018 13:29:42 -0400 Johannes Weiner <hannes@xxxxxxxxxxx> wrote:

> Right now, psi reports pressure and stall times of already concluded
> stall events. For most use cases this is current enough, but certain
> highly latency-sensitive applications, like the Android OOM killer,
> might want to know about and react to stall states before they have
> even concluded (e.g. a prolonged reclaim cycle).
> 
> This patches the procfs/cgroupfs interface such that when the pressure
> metrics are read, the current per-cpu states, if any, are taken into
> account as well.
> 
> Any ongoing states are concluded, their time snapshotted, and then
> restarted. This requires holding the rq lock to avoid corruption. It
> could use some form of rq lock ratelimiting or avoidance.
> 
> Requested-by: Suren Baghdasaryan <surenb@xxxxxxxxxx>
> Not-yet-signed-off-by: Johannes Weiner <hannes@xxxxxxxxxxx>

What-does-that-mean:?