| Message ID | 20191011134500.235736-2-douglas.raillard@arm.com (mailing list archive) |
|---|---|
| State | RFC, archived |
| Headers | show |
| Series | sched/cpufreq: Make schedutil energy aware | expand |
On 11/10/2019 15:44, Douglas RAILLARD wrote: [...] > diff --git a/include/linux/energy_model.h b/include/linux/energy_model.h > index d249b88a4d5a..dd6a35f099ea 100644 > --- a/include/linux/energy_model.h > +++ b/include/linux/energy_model.h > @@ -159,6 +159,53 @@ static inline int em_pd_nr_cap_states(struct em_perf_domain *pd) > return pd->nr_cap_states; > } > > +#define EM_COST_MARGIN_SCALE 1024U > + > +/** > + * em_pd_get_higher_freq() - Get the highest frequency that does not exceed the > + * given cost margin compared to min_freq > + * @pd : performance domain for which this must be done > + * @min_freq : minimum frequency to return > + * @cost_margin : allowed margin compared to min_freq, on the > + * EM_COST_MARGIN_SCALE scale. > + * > + * Return: the chosen frequency, guaranteed to be at least as high as min_freq. > + */ > +static inline unsigned long em_pd_get_higher_freq(struct em_perf_domain *pd, > + unsigned long min_freq, unsigned long cost_margin) > +{ > + unsigned long max_cost = 0; > + struct em_cap_state *cs; > + int i; > + > + if (!pd) > + return min_freq; > + > + /* Compute the maximum allowed cost */ > + for (i = 0; i < pd->nr_cap_states; i++) { > + cs = &pd->table[i]; > + if (cs->frequency >= min_freq) { > + max_cost = cs->cost + > + (cs->cost * cost_margin) / EM_COST_MARGIN_SCALE; > + break; > + } > + } > + > + /* Find the highest frequency that will not exceed the cost margin */ > + for (i = pd->nr_cap_states-1; i >= 0; i--) { > + cs = &pd->table[i]; > + if (cs->cost <= max_cost) > + return cs->frequency; > + } > + > + /* > + * We should normally never reach here, unless min_freq was higher than > + * the highest available frequency, which is not expected to happen. > + */ > + return min_freq; > +} > + > + Why two blank lines? > #else Doesn't apply cleanly on v5.4-rc3. There seems to be a line missing? 27871f7a8a341 (Quentin Perret 2018-12-03 09:56:16 +0000 163) struct em_perf_domain {}; [...]
On 11/10/2019 15:44, Douglas RAILLARD wrote: [...] > diff --git a/include/linux/energy_model.h b/include/linux/energy_model.h > index d249b88a4d5a..dd6a35f099ea 100644 > --- a/include/linux/energy_model.h > +++ b/include/linux/energy_model.h > @@ -159,6 +159,53 @@ static inline int em_pd_nr_cap_states(struct em_perf_domain *pd) > return pd->nr_cap_states; > } > > +#define EM_COST_MARGIN_SCALE 1024U > + > +/** > + * em_pd_get_higher_freq() - Get the highest frequency that does not exceed the > + * given cost margin compared to min_freq > + * @pd : performance domain for which this must be done > + * @min_freq : minimum frequency to return > + * @cost_margin : allowed margin compared to min_freq, on the > + * EM_COST_MARGIN_SCALE scale. > + * > + * Return: the chosen frequency, guaranteed to be at least as high as min_freq. > + */ > +static inline unsigned long em_pd_get_higher_freq(struct em_perf_domain *pd, > + unsigned long min_freq, unsigned long cost_margin) > +{ > + unsigned long max_cost = 0; > + struct em_cap_state *cs; > + int i; > + > + if (!pd) > + return min_freq; > + > + /* Compute the maximum allowed cost */ > + for (i = 0; i < pd->nr_cap_states; i++) { > + cs = &pd->table[i]; > + if (cs->frequency >= min_freq) { > + max_cost = cs->cost + > + (cs->cost * cost_margin) / EM_COST_MARGIN_SCALE; Maybe you could mention in the header that this is the place where the algorithm could be tuned. (even though it doesn't offer any tuning interface, which is a good thing). > + break; > + } > + } > + > + /* Find the highest frequency that will not exceed the cost margin */ > + for (i = pd->nr_cap_states-1; i >= 0; i--) { > + cs = &pd->table[i]; > + if (cs->cost <= max_cost) > + return cs->frequency; > + } > + > + /* > + * We should normally never reach here, unless min_freq was higher than > + * the highest available frequency, which is not expected to happen. > + */ Maybe add a WARN_ONCE(1, "foobar"); here to indicate this unlikely event (CPUfreq and EM framwork out of sync)? [...]
Hi Dietmar, On 10/17/19 10:58 AM, Dietmar Eggemann wrote: > On 11/10/2019 15:44, Douglas RAILLARD wrote: > > [...] > >> diff --git a/include/linux/energy_model.h b/include/linux/energy_model.h >> index d249b88a4d5a..dd6a35f099ea 100644 >> --- a/include/linux/energy_model.h >> +++ b/include/linux/energy_model.h >> @@ -159,6 +159,53 @@ static inline int em_pd_nr_cap_states(struct em_perf_domain *pd) >> return pd->nr_cap_states; >> } >> >> +#define EM_COST_MARGIN_SCALE 1024U >> + >> +/** >> + * em_pd_get_higher_freq() - Get the highest frequency that does not exceed the >> + * given cost margin compared to min_freq >> + * @pd : performance domain for which this must be done >> + * @min_freq : minimum frequency to return >> + * @cost_margin : allowed margin compared to min_freq, on the >> + * EM_COST_MARGIN_SCALE scale. >> + * >> + * Return: the chosen frequency, guaranteed to be at least as high as min_freq. >> + */ >> +static inline unsigned long em_pd_get_higher_freq(struct em_perf_domain *pd, >> + unsigned long min_freq, unsigned long cost_margin) >> +{ >> + unsigned long max_cost = 0; >> + struct em_cap_state *cs; >> + int i; >> + >> + if (!pd) >> + return min_freq; >> + >> + /* Compute the maximum allowed cost */ >> + for (i = 0; i < pd->nr_cap_states; i++) { >> + cs = &pd->table[i]; >> + if (cs->frequency >= min_freq) { >> + max_cost = cs->cost + >> + (cs->cost * cost_margin) / EM_COST_MARGIN_SCALE; > > Maybe you could mention in the header that this is the place where the > algorithm could be tuned. (even though it doesn't offer any tuning > interface, which is a good thing). I'm not sure what you mean, the patch "title" contains "em_pd_get_higher_freq()", should it also mention where exactly inside the function the margin logic is implemented ? >> + break; >> + } >> + } >> + >> + /* Find the highest frequency that will not exceed the cost margin */ >> + for (i = pd->nr_cap_states-1; i >= 0; i--) { >> + cs = &pd->table[i]; >> + if (cs->cost <= max_cost) >> + return cs->frequency; >> + } >> + >> + /* >> + * We should normally never reach here, unless min_freq was higher than >> + * the highest available frequency, which is not expected to happen. >> + */ > > Maybe add a WARN_ONCE(1, "foobar"); here to indicate this unlikely event > (CPUfreq and EM framwork out of sync)? Will do. > [...] >
diff --git a/include/linux/energy_model.h b/include/linux/energy_model.h index d249b88a4d5a..dd6a35f099ea 100644 --- a/include/linux/energy_model.h +++ b/include/linux/energy_model.h @@ -159,6 +159,53 @@ static inline int em_pd_nr_cap_states(struct em_perf_domain *pd) return pd->nr_cap_states; } +#define EM_COST_MARGIN_SCALE 1024U + +/** + * em_pd_get_higher_freq() - Get the highest frequency that does not exceed the + * given cost margin compared to min_freq + * @pd : performance domain for which this must be done + * @min_freq : minimum frequency to return + * @cost_margin : allowed margin compared to min_freq, on the + * EM_COST_MARGIN_SCALE scale. + * + * Return: the chosen frequency, guaranteed to be at least as high as min_freq. + */ +static inline unsigned long em_pd_get_higher_freq(struct em_perf_domain *pd, + unsigned long min_freq, unsigned long cost_margin) +{ + unsigned long max_cost = 0; + struct em_cap_state *cs; + int i; + + if (!pd) + return min_freq; + + /* Compute the maximum allowed cost */ + for (i = 0; i < pd->nr_cap_states; i++) { + cs = &pd->table[i]; + if (cs->frequency >= min_freq) { + max_cost = cs->cost + + (cs->cost * cost_margin) / EM_COST_MARGIN_SCALE; + break; + } + } + + /* Find the highest frequency that will not exceed the cost margin */ + for (i = pd->nr_cap_states-1; i >= 0; i--) { + cs = &pd->table[i]; + if (cs->cost <= max_cost) + return cs->frequency; + } + + /* + * We should normally never reach here, unless min_freq was higher than + * the highest available frequency, which is not expected to happen. + */ + return min_freq; +} + + #else struct em_data_callback {}; #define EM_DATA_CB(_active_power_cb) { } @@ -181,6 +228,12 @@ static inline int em_pd_nr_cap_states(struct em_perf_domain *pd) { return 0; } + +static inline unsigned long em_pd_get_higher_freq(struct em_perf_domain *pd, + unsigned long min_freq, unsigned long cost_margin) +{ + return min_freq; +} #endif #endif
em_pd_get_higher_freq() returns a frequency greater or equal to the provided one while taking into account a given cost margin. It also skips inefficient OPPs that have a higher cost than another one with a higher frequency. The efficiency of an OPP is measured as efficiency=capacity/power. OPPs with the same efficiency are assumed to be equivalent, since they will consume as much energy for a given amount of work to do. That may take more or less time depending on the frequency, but will consume the same energy. Signed-off-by: Douglas RAILLARD <douglas.raillard@arm.com> --- include/linux/energy_model.h | 53 ++++++++++++++++++++++++++++++++++++ 1 file changed, 53 insertions(+)