Messages in this thread | | | Date | Thu, 10 Dec 2020 13:26:39 +0000 | From | Ionela Voinescu <> | Subject | Re: [PATCH] arm64: topology: Cleanup init_amu_fie() a bit |
| |
On Thursday 10 Dec 2020 at 18:04:39 (+0530), Viresh Kumar wrote: > On 10-12-20, 11:29, Ionela Voinescu wrote: > > On Thursday 10 Dec 2020 at 16:25:06 (+0530), Viresh Kumar wrote: > > > - But right after that we call static_branch_disable() if we aren't > > > invariant (call to topology_scale_freq_invariant()), and this will > > > happen if amu_fie_cpus doesn't have all the CPUs there. Isn't it? So > > > partial amu support is already disallowed, without cpufreq. > > > > > > > This is the point that needs clarification: > > > > topology_scale_freq_invariant()) = cpufreq_supports_freq_invariance() || > > arch_freq_counters_available(cpu_online_mask); > > > > This checks if the full system is invariant. > > > > The possible scenarios are: > > > > - All online CPUs support AMUs - arch_freq_counters_available() will > > return true -> topology_scale_freq_invariant() will return true. > > > > - None of the CPUs support AMUs, or part of the CPUs support AMUs - the > > system is invariant only if cpufreq is invariant (dependent on > > whether the driver implements the proper callbacks that results in > > calling arch_set_freq_scale() in cpufreq core. > > > > - Either cpufreq does not support invariance or we don't have AMU > > support on all CPUs -> the system is not invariant so we disable > > the AMU static key that guards the calls to > > topology_scale_freq_tick() - we would not want to set a scale factor > > for only a part of the CPUs. > > > > So whether were are or are not invariant does not depend only on the AMU > > presence, but also on the cpufreq support for invariance. We have to > > disable invariance altogether (including the AMU guarding static key) > > if the system is not invariant (it no all CPUs have means to provide the > > scale). > > Okay, I think I mis-assumed that amu_fie_cpus will get set by > enable_policy_freq_counters() even for CPUs where AMU support isn't > there, it won't be though. > > Having said that, this patch, along with the minor suggestion in the > commit log, still stands fine, right ? The other patch which I sent is > probably incorrect due to the above assumption I had. >
Yes, this one is good, although I would vote for the commit message implementation. I'll wait for v2 for reviewed-by, in case you want to push something for the second patch in the same series.
Ionela.
> -- > viresh
| |