[dpdk-stable] patch 'examples/vm_power: fix OOB frequency oscillations' has been queued to LTS release 18.11.6

[Kevin Traynor]

Hi,

FYI, your patch has been queued to LTS release 18.11.6

Note it hasn't been pushed to http://dpdk.org/browse/dpdk-stable yet.
It will be pushed if I get no objections before 12/17/19. So please
shout if anyone has objections.

Also note that after the patch there's a diff of the upstream commit vs the
patch applied to the branch. This will indicate if there was any rebasing
needed to apply to the stable branch. If there were code changes for rebasing
(ie: not only metadata diffs), please double check that the rebase was
correctly done.

Queued patches are on a temporary branch at:
https://github.com/kevintraynor/dpdk-stable-queue

This queued commit can be viewed at:
https://github.com/kevintraynor/dpdk-stable-queue/commit/823157fedf327cc98327636691cc74f95fb27de6

Thanks.

Kevin.

---
>From 823157fedf327cc98327636691cc74f95fb27de6 Mon Sep 17 00:00:00 2001
From: David Hunt <david.hunt at intel.com>
Date: Wed, 24 Jul 2019 14:18:03 +0100
Subject: [PATCH] examples/vm_power: fix OOB frequency oscillations

[ upstream commit 31c9a66465ad623258c4449fea54c0b42a2deae1 ]

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")

Signed-off-by: David Hunt <david.hunt at intel.com>
Acked-by: Anatoly Burakov <anatoly.burakov at intel.com>
---
 examples/vm_power_manager/oob_monitor_x86.c | 34 +++++++++++++++++++--
 examples/vm_power_manager/power_manager.c   |  3 +-
 examples/vm_power_manager/power_manager.h   | 12 ++++++++
 3 files changed, 44 insertions(+), 5 deletions(-)

diff --git a/examples/vm_power_manager/oob_monitor_x86.c b/examples/vm_power_manager/oob_monitor_x86.c
index ebd96b205..aecfcb2eb 100644
--- a/examples/vm_power_manager/oob_monitor_x86.c
+++ b/examples/vm_power_manager/oob_monitor_x86.c
@@ -40,4 +40,5 @@ apply_policy(int core)
 	float ratio;
 	int ret;
+	int freq_window_idx, up_count = 0, i;
 
 	g_active = 0;
@@ -102,8 +103,35 @@ 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;
diff --git a/examples/vm_power_manager/power_manager.c b/examples/vm_power_manager/power_manager.c
index 318fb0255..a7e98cf40 100644
--- a/examples/vm_power_manager/power_manager.c
+++ b/examples/vm_power_manager/power_manager.c
@@ -77,4 +77,5 @@ core_info_init(void)
 	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.");
@@ -83,6 +84,4 @@ core_info_init(void)
 	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);
diff --git a/examples/vm_power_manager/power_manager.h b/examples/vm_power_manager/power_manager.h
index 605b3c8f6..3de2f7aa0 100644
--- a/examples/vm_power_manager/power_manager.h
+++ b/examples/vm_power_manager/power_manager.h
@@ -9,4 +9,13 @@
 extern "C" {
 #endif
+
+#define FREQ_WINDOW_SIZE 32
+
+enum {
+	FREQ_UNKNOWN,
+	FREQ_MIN,
+	FREQ_MAX
+};
+
 struct core_details {
 	uint64_t last_branches;
@@ -15,4 +24,7 @@ struct core_details {
 	uint16_t oob_enabled;
 	int msr_fd;
+	uint16_t freq_directions[FREQ_WINDOW_SIZE];
+	uint16_t freq_window_idx;
+	uint16_t freq_state;
 };
 
-- 
2.21.0

---
  Diff of the applied patch vs upstream commit (please double-check if non-empty:
---
--- -	2019-12-11 21:24:14.554673866 +0000
+++ 0023-examples-vm_power-fix-OOB-frequency-oscillations.patch	2019-12-11 21:24:12.624652106 +0000
@@ -1 +1 @@
-From 31c9a66465ad623258c4449fea54c0b42a2deae1 Mon Sep 17 00:00:00 2001
+From 823157fedf327cc98327636691cc74f95fb27de6 Mon Sep 17 00:00:00 2001
@@ -5,0 +6,2 @@
+[ upstream commit 31c9a66465ad623258c4449fea54c0b42a2deae1 ]
+
@@ -17 +18,0 @@
-Cc: stable at dpdk.org
@@ -77 +78 @@
-index 9d4e587b0..7b4f4b3c4 100644
+index 318fb0255..a7e98cf40 100644
@@ -80 +81 @@
-@@ -63,4 +63,5 @@ core_info_init(void)
+@@ -77,4 +77,5 @@ core_info_init(void)
@@ -86 +87 @@
-@@ -69,6 +70,4 @@ core_info_init(void)
+@@ -83,6 +84,4 @@ core_info_init(void)
@@ -94 +95 @@
-index e81a60ae5..e324766b6 100644
+index 605b3c8f6..3de2f7aa0 100644