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Message-Id: <1568708186-20260-3-git-send-email-wanpengli@tencent.com>
Date: Tue, 17 Sep 2019 16:16:26 +0800
From: Wanpeng Li <kernellwp@...il.com>
To: linux-kernel@...r.kernel.org, kvm@...r.kernel.org
Cc: Paolo Bonzini <pbonzini@...hat.com>,
Radim Krčmář <rkrcmar@...hat.com>,
Sean Christopherson <sean.j.christopherson@...el.com>,
Vitaly Kuznetsov <vkuznets@...hat.com>,
Wanpeng Li <wanpengli@...cent.com>,
Jim Mattson <jmattson@...gle.com>,
Joerg Roedel <joro@...tes.org>
Subject: [PATCH v5 3/3] KVM: LAPIC: Tune lapic_timer_advance_ns smoothly
From: Wanpeng Li <wanpengli@...cent.com>
Filter out drastic fluctuation and random fluctuation, remove
timer_advance_adjust_done altogether, the adjustment would be
continuous.
Signed-off-by: Wanpeng Li <wanpengli@...cent.com>
---
arch/x86/kvm/lapic.c | 28 ++++++++++++++--------------
arch/x86/kvm/lapic.h | 1 -
2 files changed, 14 insertions(+), 15 deletions(-)
diff --git a/arch/x86/kvm/lapic.c b/arch/x86/kvm/lapic.c
index dbbe478..323bdca 100644
--- a/arch/x86/kvm/lapic.c
+++ b/arch/x86/kvm/lapic.c
@@ -65,7 +65,9 @@
#define APIC_BROADCAST 0xFF
#define X2APIC_BROADCAST 0xFFFFFFFFul
-#define LAPIC_TIMER_ADVANCE_ADJUST_DONE 100
+static bool dynamically_adjust_timer_advance __read_mostly;
+#define LAPIC_TIMER_ADVANCE_ADJUST_MIN 100
+#define LAPIC_TIMER_ADVANCE_ADJUST_MAX 5000
#define LAPIC_TIMER_ADVANCE_ADJUST_INIT 1000
/* step-by-step approximation to mitigate fluctuation */
#define LAPIC_TIMER_ADVANCE_ADJUST_STEP 8
@@ -1485,26 +1487,25 @@ static inline void adjust_lapic_timer_advance(struct kvm_vcpu *vcpu,
u32 timer_advance_ns = apic->lapic_timer.timer_advance_ns;
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)
+ return;
+
/* too early */
if (advance_expire_delta < 0) {
ns = -advance_expire_delta * 1000000ULL;
do_div(ns, vcpu->arch.virtual_tsc_khz);
- timer_advance_ns -= min((u32)ns,
- timer_advance_ns / LAPIC_TIMER_ADVANCE_ADJUST_STEP);
+ timer_advance_ns -= ns/LAPIC_TIMER_ADVANCE_ADJUST_STEP;
} else {
/* too late */
ns = advance_expire_delta * 1000000ULL;
do_div(ns, vcpu->arch.virtual_tsc_khz);
- timer_advance_ns += min((u32)ns,
- timer_advance_ns / LAPIC_TIMER_ADVANCE_ADJUST_STEP);
+ timer_advance_ns += ns/LAPIC_TIMER_ADVANCE_ADJUST_STEP;
}
- if (abs(advance_expire_delta) < LAPIC_TIMER_ADVANCE_ADJUST_DONE)
- apic->lapic_timer.timer_advance_adjust_done = true;
- if (unlikely(timer_advance_ns > 5000)) {
+ if (unlikely(timer_advance_ns > LAPIC_TIMER_ADVANCE_ADJUST_MAX))
timer_advance_ns = LAPIC_TIMER_ADVANCE_ADJUST_INIT;
- apic->lapic_timer.timer_advance_adjust_done = false;
- }
apic->lapic_timer.timer_advance_ns = timer_advance_ns;
}
@@ -1524,7 +1525,7 @@ static void __kvm_wait_lapic_expire(struct kvm_vcpu *vcpu)
if (guest_tsc < tsc_deadline)
__wait_lapic_expire(vcpu, tsc_deadline - guest_tsc);
- if (unlikely(!apic->lapic_timer.timer_advance_adjust_done))
+ if (dynamically_adjust_timer_advance)
adjust_lapic_timer_advance(vcpu, apic->lapic_timer.advance_expire_delta);
}
@@ -2302,13 +2303,12 @@ int kvm_create_lapic(struct kvm_vcpu *vcpu, int timer_advance_ns)
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_adjust_done = false;
+ dynamically_adjust_timer_advance = true;
} else {
apic->lapic_timer.timer_advance_ns = timer_advance_ns;
- apic->lapic_timer.timer_advance_adjust_done = true;
+ dynamically_adjust_timer_advance = false;
}
-
/*
* APIC is created enabled. This will prevent kvm_lapic_set_base from
* thinking that APIC state has changed.
diff --git a/arch/x86/kvm/lapic.h b/arch/x86/kvm/lapic.h
index 50053d2..2aad7e2 100644
--- a/arch/x86/kvm/lapic.h
+++ b/arch/x86/kvm/lapic.h
@@ -35,7 +35,6 @@ struct kvm_timer {
s64 advance_expire_delta;
atomic_t pending; /* accumulated triggered timers */
bool hv_timer_in_use;
- bool timer_advance_adjust_done;
};
struct kvm_lapic {
--
2.7.4
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