| Message ID | 1568623199-5294-1-git-send-email-wanpengli@tencent.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | [v4] KVM: LAPIC: Tune lapic_timer_advance_ns smoothly | expand |
On Mon, Sep 16, 2019 at 04:39:59PM +0800, Wanpeng Li wrote: > From: Wanpeng Li <wanpengli@tencent.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@tencent.com> > --- > arch/x86/kvm/lapic.c | 26 ++++++++++++-------------- > arch/x86/kvm/lapic.h | 1 - > arch/x86/kvm/x86.c | 2 +- > arch/x86/kvm/x86.h | 1 + > 4 files changed, 14 insertions(+), 16 deletions(-) > > diff --git a/arch/x86/kvm/lapic.c b/arch/x86/kvm/lapic.c > index dbbe478..2585b86 100644 > --- a/arch/x86/kvm/lapic.c > +++ b/arch/x86/kvm/lapic.c > @@ -69,6 +69,7 @@ > #define LAPIC_TIMER_ADVANCE_ADJUST_INIT 1000 > /* step-by-step approximation to mitigate fluctuation */ > #define LAPIC_TIMER_ADVANCE_ADJUST_STEP 8 > +#define LAPIC_TIMER_ADVANCE_FILTER 5000 > > static inline int apic_test_vector(int vec, void *bitmap) > { > @@ -1482,29 +1483,28 @@ static inline void adjust_lapic_timer_advance(struct kvm_vcpu *vcpu, > s64 advance_expire_delta) > { > struct kvm_lapic *apic = vcpu->arch.apic; > - u32 timer_advance_ns = apic->lapic_timer.timer_advance_ns; > - u64 ns; > + u32 timer_advance_ns = apic->lapic_timer.timer_advance_ns, ns; Is changing 'ns' to a u32 intentionaly? It's still cast to a u32 in the calculations, and set from @advance_expire_delta. > + > + if (abs(advance_expire_delta) > LAPIC_TIMER_ADVANCE_FILTER || Shouldn't LAPIC_TIMER_ADVANCE_FILTER be used in the other "if ... > 5000" check? if (unlikely(timer_advance_ns > 5000)) And maybe name it LAPIC_TIMER_ADVANCE_MAX or something? > + abs(advance_expire_delta) < LAPIC_TIMER_ADVANCE_ADJUST_DONE) { This should be aligned with the other 'abs', e.g.: if (abs(...) || abs(...)) return > + /* filter out random fluctuations */ If you put the comment above the if statement then you can drop the parentheses. And if you're going to bother with a comment, maybe be a bit more explicit? E.g.: /* Do not adjust for tiny fluctuations or large random spikes. */ if (abs(...) || abs(...)) return; > + 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 > 5000)) > 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 +1524,7 @@ 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 (lapic_timer_advance_ns == -1) Rather than expose 'lapic_timer_advance_ns' from x86.c, what if we add a 'static bool dynamically_adjust_timer_advance __read_mostly;' in lapic.c, and have that be set in kvm_create_lapic() and checked here? That'd make this code a little more readable, would make this patch more obvious (it wasn't immediately clear why lapic_timer_advance_ns was being exposed), and would reduce the probability of unintentionally writing/corrupting the module param. > adjust_lapic_timer_advance(vcpu, apic->lapic_timer.advance_expire_delta); > } > > @@ -2302,10 +2302,8 @@ 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; > } else { > apic->lapic_timer.timer_advance_ns = timer_advance_ns; > - apic->lapic_timer.timer_advance_adjust_done = true; > } Parentheses can be dropped (unless this is converted to a local global, as above). > 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 { > diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c > index 83288ba..bb4574c 100644 > --- a/arch/x86/kvm/x86.c > +++ b/arch/x86/kvm/x86.c > @@ -141,7 +141,7 @@ module_param(tsc_tolerance_ppm, uint, S_IRUGO | S_IWUSR); > * advancement entirely. Any other value is used as-is and disables adaptive > * tuning, i.e. allows priveleged userspace to set an exact advancement time. > */ > -static int __read_mostly lapic_timer_advance_ns = -1; > +int __read_mostly lapic_timer_advance_ns = -1; > module_param(lapic_timer_advance_ns, int, S_IRUGO | S_IWUSR); > > static bool __read_mostly vector_hashing = true; > diff --git a/arch/x86/kvm/x86.h b/arch/x86/kvm/x86.h > index b5274e2..1bf2d82 100644 > --- a/arch/x86/kvm/x86.h > +++ b/arch/x86/kvm/x86.h > @@ -301,6 +301,7 @@ extern unsigned int min_timer_period_us; > > extern bool enable_vmware_backdoor; > > +extern int lapic_timer_advance_ns; > extern int pi_inject_timer; > > extern struct static_key kvm_no_apic_vcpu; > -- > 2.7.4 >
On Tue, 17 Sep 2019 at 02:55, Sean Christopherson <sean.j.christopherson@intel.com> wrote: > > On Mon, Sep 16, 2019 at 04:39:59PM +0800, Wanpeng Li wrote: > > From: Wanpeng Li <wanpengli@tencent.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@tencent.com> > > --- > > arch/x86/kvm/lapic.c | 26 ++++++++++++-------------- > > arch/x86/kvm/lapic.h | 1 - > > arch/x86/kvm/x86.c | 2 +- > > arch/x86/kvm/x86.h | 1 + > > 4 files changed, 14 insertions(+), 16 deletions(-) > > > > diff --git a/arch/x86/kvm/lapic.c b/arch/x86/kvm/lapic.c > > index dbbe478..2585b86 100644 > > --- a/arch/x86/kvm/lapic.c > > +++ b/arch/x86/kvm/lapic.c > > @@ -69,6 +69,7 @@ > > #define LAPIC_TIMER_ADVANCE_ADJUST_INIT 1000 > > /* step-by-step approximation to mitigate fluctuation */ > > #define LAPIC_TIMER_ADVANCE_ADJUST_STEP 8 > > +#define LAPIC_TIMER_ADVANCE_FILTER 5000 > > > > static inline int apic_test_vector(int vec, void *bitmap) > > { > > @@ -1482,29 +1483,28 @@ static inline void adjust_lapic_timer_advance(struct kvm_vcpu *vcpu, > > s64 advance_expire_delta) > > { > > struct kvm_lapic *apic = vcpu->arch.apic; > > - u32 timer_advance_ns = apic->lapic_timer.timer_advance_ns; > > - u64 ns; > > + u32 timer_advance_ns = apic->lapic_timer.timer_advance_ns, ns; > > Is changing 'ns' to a u32 intentionaly? It's still cast to a u32 in the > calculations, and set from @advance_expire_delta. > > > + > > + if (abs(advance_expire_delta) > LAPIC_TIMER_ADVANCE_FILTER || > > Shouldn't LAPIC_TIMER_ADVANCE_FILTER be used in the other "if ... > 5000" > check? > > if (unlikely(timer_advance_ns > 5000)) > > And maybe name it LAPIC_TIMER_ADVANCE_MAX or something? > > > + abs(advance_expire_delta) < LAPIC_TIMER_ADVANCE_ADJUST_DONE) { > > This should be aligned with the other 'abs', e.g.: > > if (abs(...) || > abs(...)) > return > > > + /* filter out random fluctuations */ > > If you put the comment above the if statement then you can drop the > parentheses. And if you're going to bother with a comment, maybe be a bit > more explicit? E.g.: > > /* Do not adjust for tiny fluctuations or large random spikes. */ > if (abs(...) || > abs(...)) > return; > > > + 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 > 5000)) > > 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 +1524,7 @@ 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 (lapic_timer_advance_ns == -1) > > Rather than expose 'lapic_timer_advance_ns' from x86.c, what if we add a > 'static bool dynamically_adjust_timer_advance __read_mostly;' in lapic.c, > and have that be set in kvm_create_lapic() and checked here? That'd make > this code a little more readable, would make this patch more obvious (it > wasn't immediately clear why lapic_timer_advance_ns was being exposed), > and would reduce the probability of unintentionally writing/corrupting the > module param. > > > adjust_lapic_timer_advance(vcpu, apic->lapic_timer.advance_expire_delta); > > } > > > > @@ -2302,10 +2302,8 @@ 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; > > } else { > > apic->lapic_timer.timer_advance_ns = timer_advance_ns; > > - apic->lapic_timer.timer_advance_adjust_done = true; > > } > > Parentheses can be dropped (unless this is converted to a local global, as > above). I just handle all the comments in the new version. Wanpeng
diff --git a/arch/x86/kvm/lapic.c b/arch/x86/kvm/lapic.c index dbbe478..2585b86 100644 --- a/arch/x86/kvm/lapic.c +++ b/arch/x86/kvm/lapic.c @@ -69,6 +69,7 @@ #define LAPIC_TIMER_ADVANCE_ADJUST_INIT 1000 /* step-by-step approximation to mitigate fluctuation */ #define LAPIC_TIMER_ADVANCE_ADJUST_STEP 8 +#define LAPIC_TIMER_ADVANCE_FILTER 5000 static inline int apic_test_vector(int vec, void *bitmap) { @@ -1482,29 +1483,28 @@ static inline void adjust_lapic_timer_advance(struct kvm_vcpu *vcpu, s64 advance_expire_delta) { struct kvm_lapic *apic = vcpu->arch.apic; - u32 timer_advance_ns = apic->lapic_timer.timer_advance_ns; - u64 ns; + u32 timer_advance_ns = apic->lapic_timer.timer_advance_ns, ns; + + if (abs(advance_expire_delta) > LAPIC_TIMER_ADVANCE_FILTER || + abs(advance_expire_delta) < LAPIC_TIMER_ADVANCE_ADJUST_DONE) { + /* filter out random fluctuations */ + 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 > 5000)) 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 +1524,7 @@ 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 (lapic_timer_advance_ns == -1) adjust_lapic_timer_advance(vcpu, apic->lapic_timer.advance_expire_delta); } @@ -2302,10 +2302,8 @@ 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; } else { apic->lapic_timer.timer_advance_ns = timer_advance_ns; - apic->lapic_timer.timer_advance_adjust_done = true; } 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 { diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c index 83288ba..bb4574c 100644 --- a/arch/x86/kvm/x86.c +++ b/arch/x86/kvm/x86.c @@ -141,7 +141,7 @@ module_param(tsc_tolerance_ppm, uint, S_IRUGO | S_IWUSR); * advancement entirely. Any other value is used as-is and disables adaptive * tuning, i.e. allows priveleged userspace to set an exact advancement time. */ -static int __read_mostly lapic_timer_advance_ns = -1; +int __read_mostly lapic_timer_advance_ns = -1; module_param(lapic_timer_advance_ns, int, S_IRUGO | S_IWUSR); static bool __read_mostly vector_hashing = true; diff --git a/arch/x86/kvm/x86.h b/arch/x86/kvm/x86.h index b5274e2..1bf2d82 100644 --- a/arch/x86/kvm/x86.h +++ b/arch/x86/kvm/x86.h @@ -301,6 +301,7 @@ extern unsigned int min_timer_period_us; extern bool enable_vmware_backdoor; +extern int lapic_timer_advance_ns; extern int pi_inject_timer; extern struct static_key kvm_no_apic_vcpu;