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SubjectRe: [PATCH] cpufreq: ondemand: Change the calculation of target frequency
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On Friday, May 31, 2013 07:33:06 PM Stratos Karafotis wrote:
> On 05/31/2013 11:51 AM, Viresh Kumar wrote:
> >> ---
> >> arch/x86/include/asm/processor.h | 29 ----------------------
> >> drivers/cpufreq/Makefile | 2 +-
> >> drivers/cpufreq/acpi-cpufreq.c | 5 ----
> >> drivers/cpufreq/cpufreq.c | 21 ----------------
> >> drivers/cpufreq/cpufreq_governor.c | 10 +-------
> >> drivers/cpufreq/cpufreq_governor.h | 1 -
> >> drivers/cpufreq/cpufreq_ondemand.c | 39 ++++++-----------------------
> >> drivers/cpufreq/mperf.c | 51 --------------------------------------
> >> drivers/cpufreq/mperf.h | 9 -------
> >> include/linux/cpufreq.h | 6 -----
> >> 10 files changed, 9 insertions(+), 164 deletions(-)
> >> delete mode 100644 drivers/cpufreq/mperf.c
> >> delete mode 100644 drivers/cpufreq/mperf.h
> >
> > I believe you should have removed other users of getavg() in a separate
> > patch and also cc'd relevant people so that you can some review comments
> > from them.
>
> I will split the patch in two. If it's OK, I will keep the removal of
> __cpufreq_driver_getavg in the original patch and move the clean up of
> APERF/MPERF support in a second patch. I will also cc relevant people.
>
>
> >> /* Check for frequency increase */
> >> - if (load_freq > od_tuners->up_threshold * policy->cur) {
> >> + if (load > od_tuners->up_threshold) {
> >
> > Chances of this getting hit are minimal now.. I don't know if keeping
> > this will change anything now :)
>
> Actually, no. This getting hit pretty often.
> Please find attached the cpufreq statistics - trans_table during build
> of 3.4 kernel. With default up_threshold (95), the transition to max
> happened many times because of load was greater than up_threshold.
> I also thought to keep this code to leave up_threshold functionality unaffected.
>
> On 05/31/2013 03:42 PM, Rafael J. Wysocki wrote:
> > On Friday, May 31, 2013 02:24:59 PM Viresh Kumar wrote:
> >>> + } else {
> >>> + /* Calculate the next frequency proportional to load */
> >>> unsigned int freq_next;
> >>> - freq_next = load_freq / od_tuners->adj_up_threshold;
> >>> + freq_next = load * policy->max / 100;
> >>
> >> Rafael asked why you believe this is the right formula and I really couldn't
> >> find an appropriate answer to that, sorry :(
> >
> > Right, it would be good to explain that.
> >
> > "Proportional to load" means C * load, so why is "policy->max / 100" *the* right C?
> >
>
> I think, finally(?) I see your point. The right C should be "policy->cpuinfo.max_freq / 100".
> This way the target frequency will be proportional to load and the calculation will
> "map" the load to CPU freq table.

That seems to mean "take the percentage of policy->cpuinfo.max_freq proportional
to the current load and use the available frequency closest to that". Is that
correct?

Rafael


--
I speak only for myself.
Rafael J. Wysocki, Intel Open Source Technology Center.


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