apply_policy(int core)
{
struct core_info *ci;
- uint64_t counter;
+ uint64_t counter = 0;
uint64_t branches, branch_misses;
- uint32_t last_branches, last_branch_misses;
- int hits_diff, miss_diff;
+ uint64_t last_branches, last_branch_misses;
+ int64_t hits_diff, miss_diff;
float ratio;
int ret;
+ int freq_window_idx, up_count = 0, i;
g_active = 0;
ci = get_core_info();
core);
branches = counter;
+ counter = 0;
ret = pread(ci->cd[core].msr_fd, &counter,
sizeof(counter), IA32_PERFCTR1);
if (ret < 0)
ci->cd[core].last_branches = branches;
ci->cd[core].last_branch_misses = branch_misses;
- hits_diff = (int)branches - (int)last_branches;
+ /*
+ * Intentional right shift to make MSB 0 to avoid
+ * possible signed overflow or truncation.
+ */
+ branches >>= 1;
+ last_branches >>= 1;
+ hits_diff = (int64_t)branches - (int64_t)last_branches;
if (hits_diff <= 0) {
/* Likely a counter overflow condition, skip this round */
return -1.0;
}
- miss_diff = (int)branch_misses - (int)last_branch_misses;
+ /*
+ * Intentional right shift to make MSB 0 to avoid
+ * possible signed overflow or truncation.
+ */
+ branch_misses >>= 1;
+ last_branch_misses >>= 1;
+ miss_diff = (int64_t)branch_misses - (int64_t)last_branch_misses;
if (miss_diff <= 0) {
/* Likely a counter overflow condition, skip this round */
return -1.0;
ratio = (float)miss_diff * (float)100 / (float)hits_diff;
- if (ratio < ci->branch_ratio_threshold)
- power_manager_scale_core_min(core);
+ /*
+ * Store the last few directions that the ratio indicates
+ * we should take. If there's on 'up', then we scale up
+ * quickly. If all indicate 'down', only then do we scale
+ * down. Each core_details struct has it's own array.
+ */
+ freq_window_idx = ci->cd[core].freq_window_idx;
+ if (ratio > ci->branch_ratio_threshold)
+ ci->cd[core].freq_directions[freq_window_idx] = 1;
else
- power_manager_scale_core_max(core);
+ ci->cd[core].freq_directions[freq_window_idx] = 0;
+
+ freq_window_idx++;
+ freq_window_idx = freq_window_idx & (FREQ_WINDOW_SIZE-1);
+ ci->cd[core].freq_window_idx = freq_window_idx;
+
+ up_count = 0;
+ for (i = 0; i < FREQ_WINDOW_SIZE; i++)
+ up_count += ci->cd[core].freq_directions[i];
+
+ if (up_count == 0) {
+ if (ci->cd[core].freq_state != FREQ_MIN) {
+ power_manager_scale_core_min(core);
+ ci->cd[core].freq_state = FREQ_MIN;
+ }
+ } else {
+ if (ci->cd[core].freq_state != FREQ_MAX) {
+ power_manager_scale_core_max(core);
+ ci->cd[core].freq_state = FREQ_MAX;
+ }
+ }
g_active = 1;
return ratio;