[PATCH v2] KVM: LAPIC: Loose fluctuation filter for auto tune lapic_timer_advance_ns

[Wanpeng Li]

From: Wanpeng Li <wanpen...@tencent.com>

5000 guest cycles delta is easy to encounter on desktop, per-vCPU 
lapic_timer_advance_ns always keeps at 1000ns initial value, lets 
loose fluctuation filter a bit to make auto tune can make some 
progress.

Signed-off-by: Wanpeng Li <wanpen...@tencent.com>
---
v1 -> v2:
 * separate defines for ns vs cycles

 arch/x86/kvm/lapic.c | 17 +++++++++--------
 1 file changed, 9 insertions(+), 8 deletions(-)

diff --git a/arch/x86/kvm/lapic.c b/arch/x86/kvm/lapic.c
index 3a3a685..7bfc3c0 100644
--- 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_EXPIRE_MIN 100
+#define LAPIC_TIMER_ADVANCE_EXPIRE_MAX 10000
+#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
 
@@ -1488,8 +1489,8 @@ static inline void adjust_lapic_timer_advance(struct 
kvm_vcpu *vcpu,
        u64 ns;
 
        /* Do not adjust for tiny fluctuations or large random spikes. */
-       if (abs(advance_expire_delta) > LAPIC_TIMER_ADVANCE_ADJUST_MAX ||
-           abs(advance_expire_delta) < LAPIC_TIMER_ADVANCE_ADJUST_MIN)
+       if (abs(advance_expire_delta) > LAPIC_TIMER_ADVANCE_EXPIRE_MAX ||
+           abs(advance_expire_delta) < LAPIC_TIMER_ADVANCE_EXPIRE_MIN)
                return;
 
        /* too early */
@@ -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;
-- 
2.7.4