Messages in this thread | | | Date | Tue, 22 Jan 2019 09:50:42 -0800 | From | Matthias Kaehlcke <> | Subject | Re: [PATCH 1/3] drivers: base: Add frequency constraint infrastructure |
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On Tue, Jan 22, 2019 at 12:39:36PM +0530, Viresh Kumar wrote: > On 18-01-19, 14:45, Matthias Kaehlcke wrote: > > On Fri, Jan 18, 2019 at 03:32:34PM +0530, Viresh Kumar wrote: > > > On 17-01-19, 17:03, Matthias Kaehlcke wrote: > > > > On Fri, Jan 11, 2019 at 02:48:34PM +0530, Viresh Kumar wrote: > > > > > +static void fcs_update(struct freq_constraints *fcs, struct freq_pair *freq, > > > > > + enum fc_event event) > > > > > +{ > > > > > + mutex_lock(&fcs->lock); > > > > > + > > > > > + if (_fcs_update(fcs, freq, event)) { > > > > > + if (fcs->callback) > > > > > + schedule_work(&fcs->work); > > > > > > > > IIUC the constraints aren't applied until the callback is executed. I > > > > wonder if a dedicated workqueue should be used instead of the system > > > > one, to avoid longer delays from other kernel entities that might > > > > 'misbehave'. Especially for thermal constraints we want a quick > > > > response. > > > > > > I thought the system workqueue should be fast enough, it contains > > > multiple threads which can all run in parallel and service this work. > > > > Ok, I was still stuck at the old one thread per CPU model, where a > > slow work would block other items in the same workqueue until it > > finishes execution. After reading a bit through > > Documentation/core-api/workqueue.rst I agree that a system workqueue > > is probably fast enough. It might be warranted though to use > > system_highpri_wq here. > > Is this really that high priority stuff ? I am not sure.
In terms of thermal it could be. But then again, thermal throttling is driven by input from thermal sensors, which often are polled with periods >= 100 ms rather than being interrupt driven, so the type of workqueue wouldn't make a major difference here. I now think it should be fine to use the normal workqueue unless problems are reported.
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