From: Wanpeng Li <[email protected]>
Filter out drastic fluctuation and random fluctuation, remove
timer_advance_adjust_done altogether, the adjustment would be
continuous.
Signed-off-by: Wanpeng Li <[email protected]>
---
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;
+
+ 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;
--
2.7.4
On Mon, Sep 16, 2019 at 04:39:59PM +0800, Wanpeng Li wrote:
> From: Wanpeng Li <[email protected]>
>
> Filter out drastic fluctuation and random fluctuation, remove
> timer_advance_adjust_done altogether, the adjustment would be
> continuous.
>
> Signed-off-by: Wanpeng Li <[email protected]>
> ---
> 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
<[email protected]> wrote:
>
> On Mon, Sep 16, 2019 at 04:39:59PM +0800, Wanpeng Li wrote:
> > From: Wanpeng Li <[email protected]>
> >
> > Filter out drastic fluctuation and random fluctuation, remove
> > timer_advance_adjust_done altogether, the adjustment would be
> > continuous.
> >
> > Signed-off-by: Wanpeng Li <[email protected]>
> > ---
> > 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