Messages in this thread | | | Date | Thu, 29 Oct 2020 16:53:47 +0530 | From | Viresh Kumar <> | Subject | Re: [PATCH v2.2 4/4] cpufreq: schedutil: Always call driver if CPUFREQ_NEED_UPDATE_LIMITS is set |
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On 29-10-20, 12:12, Rafael J. Wysocki wrote: > From: Rafael J. Wysocki <rafael.j.wysocki@intel.com> > > Because sugov_update_next_freq() may skip a frequency update even if > the need_freq_update flag has been set for the policy at hand, policy > limits updates may not take effect as expected. > > For example, if the intel_pstate driver operates in the passive mode > with HWP enabled, it needs to update the HWP min and max limits when > the policy min and max limits change, respectively, but that may not > happen if the target frequency does not change along with the limit > at hand. In particular, if the policy min is changed first, causing > the target frequency to be adjusted to it, and the policy max limit > is changed later to the same value, the HWP max limit will not be > updated to follow it as expected, because the target frequency is > still equal to the policy min limit and it will not change until > that limit is updated. > > To address this issue, modify get_next_freq() to let the driver > callback run if the CPUFREQ_NEED_UPDATE_LIMITS cpufreq driver flag > is set regardless of whether or not the new frequency to set is > equal to the previous one. > > Fixes: f6ebbcf08f37 ("cpufreq: intel_pstate: Implement passive mode with HWP enabled") > Reported-by: Zhang Rui <rui.zhang@intel.com> > Tested-by: Zhang Rui <rui.zhang@intel.com> > Cc: 5.9+ <stable@vger.kernel.org> # 5.9+ > Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com> > --- > > v2.1 -> v2.2: > * Instead of updating need_freq_update if CPUFREQ_NEED_UPDATE_LIMITS is set > in get_next_freq() and checking it again in sugov_update_next_freq(), > check CPUFREQ_NEED_UPDATE_LIMITS directly in sugov_update_next_freq(). > * Update the subject. > > v2 -> v2.1: > * Fix typo in the subject. > * Make get_next_freq() and sugov_update_next_freq() ignore the > sg_policy->next_freq == next_freq case when CPUFREQ_NEED_UPDATE_LIMITS > is set for the driver. > * Add Tested-by from Rui (this version lets the driver callback run more > often than the v2, so the behavior in the Rui's case doesn't change). > > --- > kernel/sched/cpufreq_schedutil.c | 6 ++++-- > 1 file changed, 4 insertions(+), 2 deletions(-) > > Index: linux-pm/kernel/sched/cpufreq_schedutil.c > =================================================================== > --- linux-pm.orig/kernel/sched/cpufreq_schedutil.c > +++ linux-pm/kernel/sched/cpufreq_schedutil.c > @@ -102,7 +102,8 @@ static bool sugov_should_update_freq(str > static bool sugov_update_next_freq(struct sugov_policy *sg_policy, u64 time, > unsigned int next_freq) > { > - if (sg_policy->next_freq == next_freq) > + if (sg_policy->next_freq == next_freq && > + !cpufreq_driver_test_flags(CPUFREQ_NEED_UPDATE_LIMITS)) > return false;
Since sg_policy->next_freq is used elsewhere as well, this is the best we can do here.
> sg_policy->next_freq = next_freq; > @@ -161,7 +162,8 @@ static unsigned int get_next_freq(struct > > freq = map_util_freq(util, freq, max); > > - if (freq == sg_policy->cached_raw_freq && !sg_policy->need_freq_update) > + if (freq == sg_policy->cached_raw_freq && !sg_policy->need_freq_update && > + !cpufreq_driver_test_flags(CPUFREQ_NEED_UPDATE_LIMITS)) > return sg_policy->next_freq; > > sg_policy->need_freq_update = false;
But I was wondering if instead of this we just do this here:
if (!cpufreq_driver_test_flags(CPUFREQ_NEED_UPDATE_LIMITS)) sg_policy->cached_raw_freq = freq;
And so the above check will always fail.
Acked-by: Viresh Kumar <viresh.kumar@linaro.org>
-- viresh
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