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authorMaciej S. Szmigiero <maciej.szmigiero@oracle.com>2020-03-04 14:32:48 +0300
committerRafael J. Wysocki <rafael.j.wysocki@intel.com>2020-03-14 13:39:07 +0300
commitdd52551fb786aa7371bf9fe922573deafc26287e (patch)
tree5aa2489bb1895df8e4c49cb15137ce1e3c848309 /drivers/cpuidle
parent317e5ec3ecaaa2d461d3044eb6cb9cc3a59de2f2 (diff)
downloadlinux-dd52551fb786aa7371bf9fe922573deafc26287e.tar.xz
cpuidle: haltpoll: allow force loading on hosts without the REALTIME hint
Before commit 1328edca4a14 ("cpuidle-haltpoll: Enable kvm guest polling when dedicated physical CPUs are available") the cpuidle-haltpoll driver could also be used in scenarios when the host does not advertise the KVM_HINTS_REALTIME hint. While the behavior introduced by the aforementioned commit makes sense as the default there are cases where the old behavior is desired, for example, when other kernel changes triggered by presence by this hint are unwanted, for some workloads where the latency benefit from polling overweights the loss from idle CPU capacity that otherwise would be available, or just when running under older Qemu versions that lack this hint. Let's provide a typical "force" module parameter that allows restoring the old behavior. Signed-off-by: Maciej S. Szmigiero <maciej.szmigiero@oracle.com> Reviewed-by: Marcelo Tosatti <mtosatti@redhat.com> Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Diffstat (limited to 'drivers/cpuidle')
-rw-r--r--drivers/cpuidle/cpuidle-haltpoll.c12
1 files changed, 10 insertions, 2 deletions
diff --git a/drivers/cpuidle/cpuidle-haltpoll.c b/drivers/cpuidle/cpuidle-haltpoll.c
index b0ce9bc78113..db124bc1ca2c 100644
--- a/drivers/cpuidle/cpuidle-haltpoll.c
+++ b/drivers/cpuidle/cpuidle-haltpoll.c
@@ -18,6 +18,10 @@
#include <linux/kvm_para.h>
#include <linux/cpuidle_haltpoll.h>
+static bool force __read_mostly;
+module_param(force, bool, 0444);
+MODULE_PARM_DESC(force, "Load unconditionally");
+
static struct cpuidle_device __percpu *haltpoll_cpuidle_devices;
static enum cpuhp_state haltpoll_hp_state;
@@ -90,6 +94,11 @@ static void haltpoll_uninit(void)
haltpoll_cpuidle_devices = NULL;
}
+static bool haltpool_want(void)
+{
+ return kvm_para_has_hint(KVM_HINTS_REALTIME) || force;
+}
+
static int __init haltpoll_init(void)
{
int ret;
@@ -101,8 +110,7 @@ static int __init haltpoll_init(void)
cpuidle_poll_state_init(drv);
- if (!kvm_para_available() ||
- !kvm_para_has_hint(KVM_HINTS_REALTIME))
+ if (!kvm_para_available() || !haltpool_want())
return -ENODEV;
ret = cpuidle_register_driver(drv);