Messages in this thread | | | From | "Rafael J. Wysocki" <> | Subject | Re: [PATCH v2] schedutil: Allow cpufreq requests to be made even when kthread kicked | Date | Tue, 22 May 2018 13:26:55 +0200 |
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On Tuesday, May 22, 2018 12:02:24 PM CEST Rafael J. Wysocki wrote: > On Mon, May 21, 2018 at 6:13 PM, Joel Fernandes <joel@joelfernandes.org> wrote: > > On Mon, May 21, 2018 at 10:29:52AM +0200, Rafael J. Wysocki wrote: > >> On Mon, May 21, 2018 at 7:14 AM, Viresh Kumar <viresh.kumar@linaro.org> wrote: > >> > On 18-05-18, 11:55, Joel Fernandes (Google.) wrote: > >> >> From: "Joel Fernandes (Google)" <joel@joelfernandes.org> > >> >> > >> >> Currently there is a chance of a schedutil cpufreq update request to be > >> >> dropped if there is a pending update request. This pending request can > >> >> be delayed if there is a scheduling delay of the irq_work and the wake > >> >> up of the schedutil governor kthread. > >> >> > >> >> A very bad scenario is when a schedutil request was already just made, > >> >> such as to reduce the CPU frequency, then a newer request to increase > >> >> CPU frequency (even sched deadline urgent frequency increase requests) > >> >> can be dropped, even though the rate limits suggest that its Ok to > >> >> process a request. This is because of the way the work_in_progress flag > >> >> is used. > >> >> > >> >> This patch improves the situation by allowing new requests to happen > >> >> even though the old one is still being processed. Note that in this > >> >> approach, if an irq_work was already issued, we just update next_freq > >> >> and don't bother to queue another request so there's no extra work being > >> >> done to make this happen. > >> > > >> > Now that this isn't an RFC anymore, you shouldn't have added below > >> > paragraph here. It could go to the comments section though. > >> > > >> >> I had brought up this issue at the OSPM conference and Claudio had a > >> >> discussion RFC with an alternate approach [1]. I prefer the approach as > >> >> done in the patch below since it doesn't need any new flags and doesn't > >> >> cause any other extra overhead. > >> >> > >> >> [1] https://patchwork.kernel.org/patch/10384261/ > >> >> > >> >> LGTMed-by: Viresh Kumar <viresh.kumar@linaro.org> > >> >> LGTMed-by: Juri Lelli <juri.lelli@redhat.com> > >> > > >> > Looks like a Tag you just invented ? :) > >> > >> Yeah. > >> > >> The LGTM from Juri can be converned into an ACK silently IMO. That > >> said I have added Looks-good-to: tags to a couple of commits. :-) > > > > Cool, I'll covert them to Acks :-) > > So it looks like I should expect an update of this patch, right? > > Or do you prefer the current one to be applied and work on top of it?
Well, sorry, I can't apply this one as it is racy.
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