On 17/09/19 10:16, Wanpeng Li wrote:
> From: Wanpeng Li <wanpengli@xxxxxxxxxxx>
>
> Filter out drastic fluctuation and random fluctuation, remove
> timer_advance_adjust_done altogether, the adjustment would be
> continuous.
>
> Signed-off-by: Wanpeng Li <wanpengli@xxxxxxxxxxx>
Queued, thanks (I renamed the new variable to lapic_timer_advance_dynamic).
Thanks,
Paolo
> ---
> 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 {
>
