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.
[...]
