linux-kernel - [PATCH v3 2/4] cpuidle-haltpoll: set haltpoll as preferred governor

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Date:   Sun,  8 Sep 2019 00:45:22 +0100
From:   Joao Martins <joao.m.martins@...cle.com>
To:     linux-pm@...r.kernel.org
Cc:     Joao Martins <joao.m.martins@...cle.com>,
        "Rafael J. Wysocki" <rjw@...ysocki.net>,
        Daniel Lezcano <daniel.lezcano@...aro.org>,
        linux-kernel@...r.kernel.org,
        Marcelo Tosatti <mtosatti@...hat.com>, kvm@...r.kernel.org
Subject: [PATCH v3 2/4] cpuidle-haltpoll: set haltpoll as preferred governor

Right now, guest current governors have the following ratings:

 * ladder            -> 10
 * teo               -> 19
 * menu              -> 20
 * haltpoll          -> 21
 * ladder + nohz=off -> 25

haltpoll governor got introduced and it is now the default governor given
its highest rating -- with ladder+nohz being the exception -- regardless of
idle driver in the guest. An example of an undesirable case is x86 KVM
guests with MWAIT which have intel_idle registered first, and consequently
will have haltpoll be used as governor which would get limited to a poll
state and state 1 and the other states wouldn't get used.

To keep the previous defaults we decrease rating of governor to 9 (below
current lowest rating) and thus rely on @governor switch on
cpuidle_register_driver() to tie in haltpoll idle driver and governor
together.

Signed-off-by: Joao Martins <joao.m.martins@...cle.com>
---
 drivers/cpuidle/cpuidle-haltpoll.c   | 1 +
 drivers/cpuidle/governors/haltpoll.c | 2 +-
 2 files changed, 2 insertions(+), 1 deletion(-)

diff --git a/drivers/cpuidle/cpuidle-haltpoll.c b/drivers/cpuidle/cpuidle-haltpoll.c
index 56d8ab814466..519e90d125cf 100644
--- a/drivers/cpuidle/cpuidle-haltpoll.c
+++ b/drivers/cpuidle/cpuidle-haltpoll.c
@@ -34,6 +34,7 @@ static int default_enter_idle(struct cpuidle_device *dev,
 
 static struct cpuidle_driver haltpoll_driver = {
 	.name = "haltpoll",
+	.governor = "haltpoll",
 	.owner = THIS_MODULE,
 	.states = {
 		{ /* entry 0 is for polling */ },
diff --git a/drivers/cpuidle/governors/haltpoll.c b/drivers/cpuidle/governors/haltpoll.c
index 797477bda486..7a703d2e0064 100644
--- a/drivers/cpuidle/governors/haltpoll.c
+++ b/drivers/cpuidle/governors/haltpoll.c
@@ -133,7 +133,7 @@ static int haltpoll_enable_device(struct cpuidle_driver *drv,
 
 static struct cpuidle_governor haltpoll_governor = {
 	.name =			"haltpoll",
-	.rating =		21,
+	.rating =		9,
 	.enable =		haltpoll_enable_device,
 	.select =		haltpoll_select,
 	.reflect =		haltpoll_reflect,
-- 
2.17.1