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Commit a0f0037e authored by Wanpeng Li's avatar Wanpeng Li Committed by Paolo Bonzini
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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: default avatarWanpeng Li <wanpengli@tencent.com>
Signed-off-by: default avatarPaolo Bonzini <pbonzini@redhat.com>
parent fd3edd4a

arch/x86/kvm/lapic.c

+7 −6
Original line number Diff line number Diff line
@@ -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;