KVM: LAPIC: Loosen filter for adaptive tuning of lapic_timer_advance_ns

5000 guest cycles delta is easy to encounter on desktop, per-vCPU
lapic_timer_advance_ns always keeps at 1000ns initial value, let's
loosen the filter a bit to let adaptive tuning make progress.

Signed-off-by: Wanpeng Li <wanpengli@tencent.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

diff --git a/arch/x86/kvm/lapic.c b/arch/x86/kvm/lapic.c
index 3a3a6854dccaeed071f4fa4a3800a3d002c06269..87b0fcc23ef8946f7fe2f7ab46db9c0178a706b9 100644 (file)
--- a/arch/x86/kvm/lapic.c
+++ b/arch/x86/kvm/lapic.c
@@ -66,9 +66,10 @@
 #define X2APIC_BROADCAST               0xFFFFFFFFul
 
 static bool lapic_timer_advance_dynamic __read_mostly;
-#define LAPIC_TIMER_ADVANCE_ADJUST_MIN 100
-#define LAPIC_TIMER_ADVANCE_ADJUST_MAX 5000
-#define LAPIC_TIMER_ADVANCE_ADJUST_INIT 1000
+#define LAPIC_TIMER_ADVANCE_ADJUST_MIN 100     /* clock cycles */
+#define LAPIC_TIMER_ADVANCE_ADJUST_MAX 10000   /* clock cycles */
+#define LAPIC_TIMER_ADVANCE_NS_INIT    1000
+#define LAPIC_TIMER_ADVANCE_NS_MAX     5000
 /* step-by-step approximation to mitigate fluctuation */
 #define LAPIC_TIMER_ADVANCE_ADJUST_STEP 8
 
@@ -1504,8 +1505,8 @@ static inline void adjust_lapic_timer_advance(struct kvm_vcpu *vcpu,
                timer_advance_ns += ns/LAPIC_TIMER_ADVANCE_ADJUST_STEP;
        }
 
-       if (unlikely(timer_advance_ns > LAPIC_TIMER_ADVANCE_ADJUST_MAX))
-               timer_advance_ns = LAPIC_TIMER_ADVANCE_ADJUST_INIT;
+       if (unlikely(timer_advance_ns > LAPIC_TIMER_ADVANCE_NS_MAX))
+               timer_advance_ns = LAPIC_TIMER_ADVANCE_NS_INIT;
        apic->lapic_timer.timer_advance_ns = timer_advance_ns;
 }
 
@@ -2302,7 +2303,7 @@ int kvm_create_lapic(struct kvm_vcpu *vcpu, int timer_advance_ns)
                     HRTIMER_MODE_ABS_HARD);
        apic->lapic_timer.timer.function = apic_timer_fn;
        if (timer_advance_ns == -1) {
-               apic->lapic_timer.timer_advance_ns = LAPIC_TIMER_ADVANCE_ADJUST_INIT;
+               apic->lapic_timer.timer_advance_ns = LAPIC_TIMER_ADVANCE_NS_INIT;
                lapic_timer_advance_dynamic = true;
        } else {
                apic->lapic_timer.timer_advance_ns = timer_advance_ns;