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examples/vm_power: fix OOB frequency oscillations

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The branch ratio algorithm in the vm_power_manager sample application
can be very sensitive at patricular loads in a workload, causing
oscillations between min and max frequency. For example, if a
workload is at 50%, scaling up may change the ratio
enough that it immediately thinks it needs to scale down again.

This patch introduces a sliding window recording the scale up/down
direction for the last 32 samples, and scales up if any samples indicate
we should scale up, otherwise scale down. Each core has it's own window.

Fixes: 4b1a631b8a8a ("examples/vm_power: add oob monitoring functions")
Cc: stable@dpdk.org

Signed-off-by: David Hunt <david.hunt@intel.com>
Acked-by: Anatoly Burakov <anatoly.burakov@intel.com>
This commit is contained in:
David Hunt 2019-07-24 14:18:03 +01:00 committed by Thomas Monjalon
parent eccc5d3237
commit 31c9a66465
3 changed files with 44 additions and 5 deletions
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34
examples/vm_power_manager/oob_monitor_x86.c
View File

@ -39,6 +39,7 @@ apply_policy(int core)
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();
@ -101,10 +102,37 @@ apply_policy(int core)
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;

3
examples/vm_power_manager/power_manager.c
View File

@ -62,14 +62,13 @@ core_info_init(void)
ci->core_count = get_nprocs_conf();
ci->branch_ratio_threshold = BRANCH_RATIO_THRESHOLD;
ci->cd = malloc(ci->core_count * sizeof(struct core_details));
memset(ci->cd, 0, ci->core_count * sizeof(struct core_details));
if (!ci->cd) {
RTE_LOG(ERR, POWER_MANAGER, "Failed to allocate memory for core info.");
return -1;
}
for (i = 0; i < ci->core_count; i++) {
ci->cd[i].global_enabled_cpus = 1;
ci->cd[i].oob_enabled = 0;
ci->cd[i].msr_fd = 0;
}
printf("%d cores in system\n", ci->core_count);
return 0;

12
examples/vm_power_manager/power_manager.h
View File

@ -8,12 +8,24 @@
#ifdef __cplusplus
extern "C" {
#endif
#define FREQ_WINDOW_SIZE 32
enum {
FREQ_UNKNOWN,
FREQ_MIN,
FREQ_MAX
};
struct core_details {
uint64_t last_branches;
uint64_t last_branch_misses;
uint16_t global_enabled_cpus;
uint16_t oob_enabled;
int msr_fd;
uint16_t freq_directions[FREQ_WINDOW_SIZE];
uint16_t freq_window_idx;
uint16_t freq_state;
};
struct core_info {