On 08-12-20, 14:32, Viresh Kumar wrote: > On 07-12-20, 17:35, Rafael J. Wysocki wrote: > > From: Rafael J. Wysocki <[email protected]> > > > > First off, some cpufreq drivers (eg. intel_pstate) can pass hints > > beyond the current target frequency to the hardware and there are no > > provisions for doing that in the cpufreq framework. In particular, > > today the driver has to assume that it should not allow the frequency > > to fall below the one requested by the governor (or the required > > capacity may not be provided) which may not be the case and which may > > lead to excessive energy usage in some scenarios. > > > > Second, the hints passed by these drivers to the hardware need not be > > in terms of the frequency, so representing the utilization numbers > > coming from the scheduler as frequency before passing them to those > > drivers is not really useful. > > > > Address the two points above by adding a special-purpose replacement > > for the ->fast_switch callback, called ->adjust_perf, allowing the > > governor to pass abstract performance level (rather than frequency) > > values for the minimum (required) and target (desired) performance > > along with the CPU capacity to compare them to. > > > > Also update the schedutil governor to use the new callback instead > > of ->fast_switch if present. > > > > Signed-off-by: Rafael J. Wysocki <[email protected]> > > --- > > > > Changes with respect to the RFC: > > - Don't pass "busy" to ->adjust_perf(). > > - Use a special 'update_util' hook for the ->adjust_perf() case in > > schedutil (this still requires an additional branch because of the > > shared common code between this case and the "frequency" one, but > > IMV this version is cleaner nevertheless). > > > > --- > > drivers/cpufreq/cpufreq.c | 40 ++++++++++++++++++++++++++++++++ > > include/linux/cpufreq.h | 14 +++++++++++ > > include/linux/sched/cpufreq.h | 5 ++++ > > kernel/sched/cpufreq_schedutil.c | 48 > > +++++++++++++++++++++++++++++++-------- > > 4 files changed, 98 insertions(+), 9 deletions(-) > > > > Index: linux-pm/include/linux/cpufreq.h > > =================================================================== > > --- linux-pm.orig/include/linux/cpufreq.h > > +++ linux-pm/include/linux/cpufreq.h > > @@ -320,6 +320,15 @@ struct cpufreq_driver { > > unsigned int index); > > unsigned int (*fast_switch)(struct cpufreq_policy *policy, > > unsigned int target_freq); > > + /* > > + * ->fast_switch() replacement for drivers that use an internal > > + * representation of performance levels and can pass hints other than > > + * the target performance level to the hardware. > > + */ > > + void (*adjust_perf)(unsigned int cpu, > > + unsigned long min_perf, > > + unsigned long target_perf, > > + unsigned long capacity); > > With this callback in place, do we still need to keep the other stuff we > introduced recently, like CPUFREQ_NEED_UPDATE_LIMITS ?
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