Messages in this thread | | | From | Vincent Guittot <> | Date | Wed, 30 Nov 2022 11:42:20 +0100 | Subject | Re: [PATCH v1] Revert "cpufreq: schedutil: Move max CPU capacity to sugov_policy" |
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Hi All
Just for the log and because it took me a while to figure out the root cause of the problem: This patch also creates a regression for snapdragon845 based systems and probably on any QC chipsets that use a LUT to update the OPP table at boot. The behavior is the same as described by Sam with a staled value in sugov_policy.max field.
Regards, Vincent
On Tue, 22 Nov 2022 at 09:58, Lukasz Luba <lukasz.luba@arm.com> wrote: > > Hi Rafael and Sam > > On 11/21/22 19:18, Rafael J. Wysocki wrote: > > On Fri, Nov 18, 2022 at 2:00 AM Sam Wu <wusamuel@google.com> wrote: > >> > >> On Wed, Nov 16, 2022 at 3:35 AM Lukasz Luba <lukasz.luba@arm.com> wrote: > >>> Which mainline kernel version you use in pixel6? > >> I am using kernel version 6.1-rc5. > >>> > >>> Could you elaborate a bit how is it possible? > >>> Do you have the sg_policy setup properly (and at right time)? > >>> Do you have the cpu capacity from arch_scale_cpu_capacity() > >>> set correctly and at the right time during this cpufreq > >>> governor setup? > >>> > >>> IIRC in Android there is a different code for setting up the > >>> cpufreq sched governor clones. In mainline we don't have to do > >>> those tricks, so this might be the main difference. > >> This behavior is seen on the mainline kernel. There isn't any vendor code > >> modifying the behavior, and the schedutil governor is being used. > >>> > >>> Could you trace the value that is read from > >>> arch_scale_cpu_capacity() and share it with us? > >>> I suspect this value changes in time in your kernel. > >> There's an additional CPU capacity normalization step during > >> init_cpu_capacity_callback() that does not happen until all the CPUs come > >> online. However, the sugov_start() function can be called for a subset of > >> CPUs before all the CPUs are brought up and before the normalization of > >> the CPU capacity values, so there could be a stale value stored > >> in sugov_policy.max field. > > > > OK, the revert has been applied as 6.1-rc material, thanks! > > I was on a business trip last week so couldn't check this. > Now I'm back and I've checked the booting sequence. > Yes, there is some race condition and the mechanism > using blocking_notifier_call_chain() in the cpufreq_online() > doesn't help while we are registering that schedutil > new policy. > > I will have to go through those mechanisms and check them. > I agree, for now the best option is to revert the patch. > > My apologies for introducing this issues. > Thanks Sam for capturing it. > > Regards, > Lukasz
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