From: Viresh Kumar <viresh.kumar@linaro.org>
To: Doug Smythies <dsmythies@telus.net>
Cc: linux-pm@vger.kernel.org,
'Vincent Guittot' <vincent.guittot@linaro.org>,
linux-kernel@vger.kernel.org,
'Rafael Wysocki' <rjw@rjwysocki.net>,
'Srinivas Pandruvada' <srinivas.pandruvada@linux.intel.com>,
'Len Brown' <lenb@kernel.org>
Subject: Re: [PATCH V4 2/2] cpufreq: intel_pstate: Implement QoS supported freq constraints
Date: Fri, 9 Aug 2019 12:21:06 +0530 [thread overview]
Message-ID: <20190809065106.vpktdp44qohdt3jk@vireshk-i7> (raw)
In-Reply-To: <001f01d54e7c$a22395d0$e66ac170$@net>
On 08-08-19, 23:35, Doug Smythies wrote:
> O.K. While I understand the explanations, I still struggle with
> this scenario:
>
> doug@s15:~/temp$ cat /sys/devices/system/cpu/intel_pstate/max_perf_pct
> 50 <<< Note: 50% = 1.9 GHz in my system)
> doug@s15:~/temp$ grep . /sys/devices/system/cpu/cpufreq/policy*/scaling_max_freq
> /sys/devices/system/cpu/cpufreq/policy0/scaling_max_freq:1900000
> /sys/devices/system/cpu/cpufreq/policy1/scaling_max_freq:1900000
> /sys/devices/system/cpu/cpufreq/policy2/scaling_max_freq:1900000
> /sys/devices/system/cpu/cpufreq/policy3/scaling_max_freq:1900000
> /sys/devices/system/cpu/cpufreq/policy4/scaling_max_freq:1900000
> /sys/devices/system/cpu/cpufreq/policy5/scaling_max_freq:1900000
> /sys/devices/system/cpu/cpufreq/policy6/scaling_max_freq:1900000
> /sys/devices/system/cpu/cpufreq/policy7/scaling_max_freq:1900000
>
> At this point I am not certain what I'll get if I try to
> set max_perf_pct to 100%, nor do I know how to find out
> with a user command.
>
> So, I'll try it:
>
> doug@s15:~/temp$ echo 100 | sudo tee /sys/devices/system/cpu/intel_pstate/max_perf_pct
> 100
> doug@s15:~/temp$ cat /sys/devices/system/cpu/intel_pstate/max_perf_pct
> 100 <<< Note: 100% = 3.8 GHz in my system)
> doug@s15:~/temp$ grep . /sys/devices/system/cpu/cpufreq/policy*/scaling_max_freq
> /sys/devices/system/cpu/cpufreq/policy0/scaling_max_freq:2200000
> /sys/devices/system/cpu/cpufreq/policy1/scaling_max_freq:2200000
> /sys/devices/system/cpu/cpufreq/policy2/scaling_max_freq:2200000
> /sys/devices/system/cpu/cpufreq/policy3/scaling_max_freq:2200000
> /sys/devices/system/cpu/cpufreq/policy4/scaling_max_freq:2200000
> /sys/devices/system/cpu/cpufreq/policy5/scaling_max_freq:2200000
> /sys/devices/system/cpu/cpufreq/policy6/scaling_max_freq:2200000
> /sys/devices/system/cpu/cpufreq/policy7/scaling_max_freq:2200000
>
> I guess I had set it sometime earlier, forgot, and then didn't
> get 3.8 Ghz as I had expected via max_perf_pct.
Right, so the problem here (since ages) is that there is no file in
sysfs to show the value earlier set by the user to
scaling_max/min_freq. Rather when you try to read those files, cpufreq
core gives you the current value of policy->min/max, which can come
from so many factors, like userspace, thermal, max_perf_pct, etc.
You saw 2200000 here because you must have set that value to
scaling_max_freq earlier, else maybe thermal or other stuff
constrained that value for you.
Though the cpufreq core stores the value set by user and uses it to
recalculate policy->max using it. To get rid of your constraint, set
scaling_max_freq to the highest frequency and you will be good.
--
viresh
next prev parent reply other threads:[~2019-08-09 6:51 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-08-07 7:06 [PATCH V4 1/2] cpufreq: schedutil: Don't skip freq update when limits change Viresh Kumar
2019-08-07 7:06 ` [PATCH V4 2/2] cpufreq: intel_pstate: Implement QoS supported freq constraints Viresh Kumar
2019-08-08 16:25 ` Doug Smythies
2019-08-08 16:46 ` Rafael J. Wysocki
2019-08-09 2:16 ` Viresh Kumar
2019-08-09 6:35 ` Doug Smythies
2019-08-09 6:51 ` Viresh Kumar [this message]
2019-08-09 2:22 ` [PATCH V5 " Viresh Kumar
2019-08-09 5:48 ` Doug Smythies
2019-08-26 9:18 ` Rafael J. Wysocki
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