From: Zhang Rui <rui.zhang@intel.com>
To: rjw@rjwysocki.net, daniel.lezcano@linaro.org
Cc: linux-pm@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: [RFC PATCH 2/3] cpuidle: ladder: Tune promotion/demotion threshold
Date: Sun, 6 Nov 2022 01:42:24 +0800 [thread overview]
Message-ID: <20221105174225.28673-2-rui.zhang@intel.com> (raw)
In-Reply-To: <20221105174225.28673-1-rui.zhang@intel.com>
After fixing the bogus comparison between u64 and s64, the ladder
governor stops making promotion decisions errornously.
However, after this, it is found that the ladder governor demotes much
easier than promotes.
Below is captured using turbostat after a 30 seconds runtime idle,
Without previous patch,
Busy% IRQ POLL C1 C1E C3 C6 C7s C8 C9 C10 CPU%c1 CPU%c3 CPU%c6 CPU%c7 PkgWatt
0.30 2373 0 0 0 4 9 25 122 326 2857 0.36 0.04 0.57 98.73 1.48
With previous patch,
Busy% IRQ POLL C1 C1E C3 C6 C7s C8 C9 C10 CPU%c1 CPU%c3 CPU%c6 CPU%c7 PkgWatt
0.42 3071 0 771 838 447 327 336 382 299 344 34.18 16.21 17.69 31.51 2.00
And this is caused by the imbalanced PROMOTION_COUNT/DEMOTION_COUNT.
With this patch,
Busy% IRQ POLL C1 C1E C3 C6 C7s C8 C9 C10 CPU%c1 CPU%c3 CPU%c6 CPU%c7 PkgWatt
0.39 2436 0 1 72 177 51 194 243 799 1883 0.50 0.32 0.35 98.45 1.53
Note that this is an experimental patch to illustrate the problem,
and it is checked with idle scenario only for now.
I will try to evaluate with more scenarios, and if someone can help
evaluate with more scenarios at the same time and provide data for the
benefit with different PROMOTION_COUNT/DEMOTION_COUNT values, that
would be great.
Signed-off-by: Zhang Rui <rui.zhang@intel.com>
---
drivers/cpuidle/governors/ladder.c | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)
diff --git a/drivers/cpuidle/governors/ladder.c b/drivers/cpuidle/governors/ladder.c
index fb61118aef37..4b47aa0a4da9 100644
--- a/drivers/cpuidle/governors/ladder.c
+++ b/drivers/cpuidle/governors/ladder.c
@@ -20,8 +20,8 @@
#include <asm/io.h>
#include <linux/uaccess.h>
-#define PROMOTION_COUNT 4
-#define DEMOTION_COUNT 1
+#define PROMOTION_COUNT 2
+#define DEMOTION_COUNT 4
struct ladder_device_state {
struct {
--
2.25.1
next prev parent reply other threads:[~2022-11-05 17:40 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-11-05 17:42 [RFC PATCH 1/3] cpuidle: ladder: Fix bogus comparison between s64 and u64 Zhang Rui
2022-11-05 17:42 ` Zhang Rui [this message]
2022-11-23 17:50 ` [RFC PATCH 2/3] cpuidle: ladder: Tune promotion/demotion threshold Rafael J. Wysocki
2022-11-23 23:53 ` Doug Smythies
2022-11-25 6:38 ` Zhang Rui
2022-11-25 13:36 ` Rafael J. Wysocki
2022-11-27 3:18 ` Zhang Rui
2022-11-05 17:42 ` [RFC PATCH 3/3] cpuidle: ladder: Fix handling for disabled states Zhang Rui
2022-11-23 17:56 ` Rafael J. Wysocki
2022-11-23 17:37 ` [RFC PATCH 1/3] cpuidle: ladder: Fix bogus comparison between s64 and u64 Rafael J. Wysocki
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