[PATCH] x86/hyper-v: enable TSC page clocksource on 32bit

[PATCH] x86/hyper-v: enable TSC page clocksource on 32bit

[Vitaly Kuznetsov]

There is no particular reason to not enable TSC page clocksource
on 32-bit. mul_u64_u64_shr() is available and despite the increased
computational complexity (compared to 64bit) TSC page is still a huge
win compared to MSR-based clocksource.

In-kernel reads:
  MSR based clocksource: 3361 cycles
  TSC page clocksource: 49 cycles

Reads from userspace (unilizing vDSO in case of TSC page):
  MSR based clocksource: 5664 cycles
  TSC page clocksource: 131 cycles

Enabling TSC page on 32bits allows us to get rid of CONFIG_HYPERV_TSCPAGE
as it is now not any different from CONFIG_HYPERV_TIMER.

Signed-off-by: Vitaly Kuznetsov <vkuznets@redhat.com>
---
 arch/x86/include/asm/vdso/gettimeofday.h |  6 +++---
 drivers/clocksource/hyperv_timer.c       | 11 -----------
 drivers/hv/Kconfig                       |  3 ---
 include/clocksource/hyperv_timer.h       |  6 ++----
 4 files changed, 5 insertions(+), 21 deletions(-)

diff --git a/arch/x86/include/asm/vdso/gettimeofday.h b/arch/x86/include/asm/vdso/gettimeofday.h
index ba71a63cdac4..e9ee139cf29e 100644
--- a/arch/x86/include/asm/vdso/gettimeofday.h
+++ b/arch/x86/include/asm/vdso/gettimeofday.h
@@ -51,7 +51,7 @@ extern struct pvclock_vsyscall_time_info pvclock_page
 	__attribute__((visibility("hidden")));
 #endif
 
-#ifdef CONFIG_HYPERV_TSCPAGE
+#ifdef CONFIG_HYPERV_TIMER
 extern struct ms_hyperv_tsc_page hvclock_page
 	__attribute__((visibility("hidden")));
 #endif
@@ -228,7 +228,7 @@ static u64 vread_pvclock(void)
 }
 #endif
 
-#ifdef CONFIG_HYPERV_TSCPAGE
+#ifdef CONFIG_HYPERV_TIMER
 static u64 vread_hvclock(void)
 {
 	return hv_read_tsc_page(&hvclock_page);
@@ -251,7 +251,7 @@ static inline u64 __arch_get_hw_counter(s32 clock_mode)
 		return vread_pvclock();
 	}
 #endif
-#ifdef CONFIG_HYPERV_TSCPAGE
+#ifdef CONFIG_HYPERV_TIMER
 	if (clock_mode == VCLOCK_HVCLOCK) {
 		barrier();
 		return vread_hvclock();
diff --git a/drivers/clocksource/hyperv_timer.c b/drivers/clocksource/hyperv_timer.c
index ba2c79e6a0ee..b6083faab540 100644
--- a/drivers/clocksource/hyperv_timer.c
+++ b/drivers/clocksource/hyperv_timer.c
@@ -212,8 +212,6 @@ EXPORT_SYMBOL_GPL(hv_stimer_global_cleanup);
 struct clocksource *hyperv_cs;
 EXPORT_SYMBOL_GPL(hyperv_cs);
 
-#ifdef CONFIG_HYPERV_TSCPAGE
-
 static struct ms_hyperv_tsc_page *tsc_pg;
 
 struct ms_hyperv_tsc_page *hv_get_tsc_page(void)
@@ -244,7 +242,6 @@ static struct clocksource hyperv_cs_tsc = {
 	.mask	= CLOCKSOURCE_MASK(64),
 	.flags	= CLOCK_SOURCE_IS_CONTINUOUS,
 };
-#endif
 
 static u64 notrace read_hv_sched_clock_msr(void)
 {
@@ -271,7 +268,6 @@ static struct clocksource hyperv_cs_msr = {
 	.flags	= CLOCK_SOURCE_IS_CONTINUOUS,
 };
 
-#ifdef CONFIG_HYPERV_TSCPAGE
 static bool __init hv_init_tsc_clocksource(void)
 {
 	u64		tsc_msr;
@@ -306,13 +302,6 @@ static bool __init hv_init_tsc_clocksource(void)
 	sched_clock_register(read_hv_sched_clock_tsc, 64, HV_CLOCK_HZ);
 	return true;
 }
-#else
-static bool __init hv_init_tsc_clocksource(void)
-{
-	return false;
-}
-#endif
-
 
 void __init hv_init_clocksource(void)
 {
diff --git a/drivers/hv/Kconfig b/drivers/hv/Kconfig
index 9a59957922d4..79e5356a737a 100644
--- a/drivers/hv/Kconfig
+++ b/drivers/hv/Kconfig
@@ -14,9 +14,6 @@ config HYPERV
 config HYPERV_TIMER
 	def_bool HYPERV
 
-config HYPERV_TSCPAGE
-       def_bool HYPERV && X86_64
-
 config HYPERV_UTILS
 	tristate "Microsoft Hyper-V Utilities driver"
 	depends on HYPERV && CONNECTOR && NLS
diff --git a/include/clocksource/hyperv_timer.h b/include/clocksource/hyperv_timer.h
index a821deb8ecb2..f72e4619d0a7 100644
--- a/include/clocksource/hyperv_timer.h
+++ b/include/clocksource/hyperv_timer.h
@@ -28,12 +28,10 @@ extern void hv_stimer_cleanup(unsigned int cpu);
 extern void hv_stimer_global_cleanup(void);
 extern void hv_stimer0_isr(void);
 
-#if IS_ENABLED(CONFIG_HYPERV)
+#ifdef CONFIG_HYPERV_TIMER
 extern struct clocksource *hyperv_cs;
 extern void hv_init_clocksource(void);
-#endif /* CONFIG_HYPERV */
 
-#ifdef CONFIG_HYPERV_TSCPAGE
 extern struct ms_hyperv_tsc_page *hv_get_tsc_page(void);
 
 static inline notrace u64
@@ -102,6 +100,6 @@ static inline u64 hv_read_tsc_page_tsc(const struct ms_hyperv_tsc_page *tsc_pg,
 {
 	return U64_MAX;
 }
-#endif /* CONFIG_HYPERV_TSCPAGE */
+#endif /* CONFIG_HYPERV_TIMER */
 
 #endif
-- 
2.20.1

RE: [PATCH] x86/hyper-v: enable TSC page clocksource on 32bit

[Michael Kelley]

From: Vitaly Kuznetsov <vkuznets@redhat.com> Sent: Wednesday, August 21, 2019 2:57 AM
> 
> There is no particular reason to not enable TSC page clocksource
> on 32-bit. mul_u64_u64_shr() is available and despite the increased
> computational complexity (compared to 64bit) TSC page is still a huge
> win compared to MSR-based clocksource.
> 
> In-kernel reads:
>   MSR based clocksource: 3361 cycles
>   TSC page clocksource: 49 cycles
> 
> Reads from userspace (unilizing vDSO in case of TSC page):

s/unilizing/utilizing/

>   MSR based clocksource: 5664 cycles
>   TSC page clocksource: 131 cycles
> 
> Enabling TSC page on 32bits allows us to get rid of CONFIG_HYPERV_TSCPAGE
> as it is now not any different from CONFIG_HYPERV_TIMER.
> 
> Signed-off-by: Vitaly Kuznetsov <vkuznets@redhat.com>
> ---
>  arch/x86/include/asm/vdso/gettimeofday.h |  6 +++---
>  drivers/clocksource/hyperv_timer.c       | 11 -----------
>  drivers/hv/Kconfig                       |  3 ---
>  include/clocksource/hyperv_timer.h       |  6 ++----
>  4 files changed, 5 insertions(+), 21 deletions(-)
> 
> diff --git a/arch/x86/include/asm/vdso/gettimeofday.h
> b/arch/x86/include/asm/vdso/gettimeofday.h
> index ba71a63cdac4..e9ee139cf29e 100644
> --- a/arch/x86/include/asm/vdso/gettimeofday.h
> +++ b/arch/x86/include/asm/vdso/gettimeofday.h
> @@ -51,7 +51,7 @@ extern struct pvclock_vsyscall_time_info pvclock_page
>  	__attribute__((visibility("hidden")));
>  #endif
> 
> -#ifdef CONFIG_HYPERV_TSCPAGE
> +#ifdef CONFIG_HYPERV_TIMER
>  extern struct ms_hyperv_tsc_page hvclock_page
>  	__attribute__((visibility("hidden")));
>  #endif
> @@ -228,7 +228,7 @@ static u64 vread_pvclock(void)
>  }
>  #endif
> 
> -#ifdef CONFIG_HYPERV_TSCPAGE
> +#ifdef CONFIG_HYPERV_TIMER
>  static u64 vread_hvclock(void)
>  {
>  	return hv_read_tsc_page(&hvclock_page);
> @@ -251,7 +251,7 @@ static inline u64 __arch_get_hw_counter(s32 clock_mode)
>  		return vread_pvclock();
>  	}
>  #endif
> -#ifdef CONFIG_HYPERV_TSCPAGE
> +#ifdef CONFIG_HYPERV_TIMER
>  	if (clock_mode == VCLOCK_HVCLOCK) {
>  		barrier();
>  		return vread_hvclock();
> diff --git a/drivers/clocksource/hyperv_timer.c b/drivers/clocksource/hyperv_timer.c
> index ba2c79e6a0ee..b6083faab540 100644
> --- a/drivers/clocksource/hyperv_timer.c
> +++ b/drivers/clocksource/hyperv_timer.c
> @@ -212,8 +212,6 @@ EXPORT_SYMBOL_GPL(hv_stimer_global_cleanup);
>  struct clocksource *hyperv_cs;
>  EXPORT_SYMBOL_GPL(hyperv_cs);
> 
> -#ifdef CONFIG_HYPERV_TSCPAGE
> -
>  static struct ms_hyperv_tsc_page *tsc_pg;
> 
>  struct ms_hyperv_tsc_page *hv_get_tsc_page(void)
> @@ -244,7 +242,6 @@ static struct clocksource hyperv_cs_tsc = {
>  	.mask	= CLOCKSOURCE_MASK(64),
>  	.flags	= CLOCK_SOURCE_IS_CONTINUOUS,
>  };
> -#endif
> 
>  static u64 notrace read_hv_sched_clock_msr(void)
>  {
> @@ -271,7 +268,6 @@ static struct clocksource hyperv_cs_msr = {
>  	.flags	= CLOCK_SOURCE_IS_CONTINUOUS,
>  };
> 
> -#ifdef CONFIG_HYPERV_TSCPAGE
>  static bool __init hv_init_tsc_clocksource(void)
>  {
>  	u64		tsc_msr;
> @@ -306,13 +302,6 @@ static bool __init hv_init_tsc_clocksource(void)
>  	sched_clock_register(read_hv_sched_clock_tsc, 64, HV_CLOCK_HZ);
>  	return true;
>  }
> -#else
> -static bool __init hv_init_tsc_clocksource(void)
> -{
> -	return false;
> -}
> -#endif
> -
> 
>  void __init hv_init_clocksource(void)
>  {
> diff --git a/drivers/hv/Kconfig b/drivers/hv/Kconfig
> index 9a59957922d4..79e5356a737a 100644
> --- a/drivers/hv/Kconfig
> +++ b/drivers/hv/Kconfig
> @@ -14,9 +14,6 @@ config HYPERV
>  config HYPERV_TIMER
>  	def_bool HYPERV
> 
> -config HYPERV_TSCPAGE
> -       def_bool HYPERV && X86_64
> -
>  config HYPERV_UTILS
>  	tristate "Microsoft Hyper-V Utilities driver"
>  	depends on HYPERV && CONNECTOR && NLS
> diff --git a/include/clocksource/hyperv_timer.h b/include/clocksource/hyperv_timer.h
> index a821deb8ecb2..f72e4619d0a7 100644
> --- a/include/clocksource/hyperv_timer.h
> +++ b/include/clocksource/hyperv_timer.h
> @@ -28,12 +28,10 @@ extern void hv_stimer_cleanup(unsigned int cpu);
>  extern void hv_stimer_global_cleanup(void);
>  extern void hv_stimer0_isr(void);
> 
> -#if IS_ENABLED(CONFIG_HYPERV)
> +#ifdef CONFIG_HYPERV_TIMER
>  extern struct clocksource *hyperv_cs;
>  extern void hv_init_clocksource(void);
> -#endif /* CONFIG_HYPERV */
> 
> -#ifdef CONFIG_HYPERV_TSCPAGE
>  extern struct ms_hyperv_tsc_page *hv_get_tsc_page(void);
> 
>  static inline notrace u64
> @@ -102,6 +100,6 @@ static inline u64 hv_read_tsc_page_tsc(const struct
> ms_hyperv_tsc_page *tsc_pg,
>  {
>  	return U64_MAX;
>  }
> -#endif /* CONFIG_HYPERV_TSCPAGE */
> +#endif /* CONFIG_HYPERV_TIMER */

There's a #else prior to the #endif that has TSCPAGE misspelled
as TSC_PAGE in the comment.  Should probably fix the comment ...

> 
>  #endif
> --
> 2.20.1

Overall an excellent removal of unnecessary complexity.  Thx.
Two minor nits notwithstanding,

Reviewed-by: Michael Kelley <mikelley@microsoft.com>

Re: [PATCH] x86/hyper-v: enable TSC page clocksource on 32bit

[Thomas Gleixner]

On Wed, 21 Aug 2019, Vitaly Kuznetsov wrote:

> There is no particular reason to not enable TSC page clocksource
> on 32-bit. mul_u64_u64_shr() is available and despite the increased
> computational complexity (compared to 64bit) TSC page is still a huge
> win compared to MSR-based clocksource.
> 
> In-kernel reads:
>   MSR based clocksource: 3361 cycles
>   TSC page clocksource: 49 cycles
> 
> Reads from userspace (unilizing vDSO in case of TSC page):
>   MSR based clocksource: 5664 cycles
>   TSC page clocksource: 131 cycles
> 
> Enabling TSC page on 32bits allows us to get rid of CONFIG_HYPERV_TSCPAGE

s/allows us/allows/

> as it is now not any different from CONFIG_HYPERV_TIMER.
> 
> Signed-off-by: Vitaly Kuznetsov <vkuznets@redhat.com>
> ---
>  arch/x86/include/asm/vdso/gettimeofday.h |  6 +++---
>  drivers/clocksource/hyperv_timer.c       | 11 -----------
>  drivers/hv/Kconfig                       |  3 ---
>  include/clocksource/hyperv_timer.h       |  6 ++----
>  4 files changed, 5 insertions(+), 21 deletions(-)

Really nice cleanup as a side effect of adding functionality.

Thanks,

	tglx

Re: [PATCH] x86/hyper-v: enable TSC page clocksource on 32bit

[Thomas Gleixner]

On Wed, 21 Aug 2019, Thomas Gleixner wrote:

> On Wed, 21 Aug 2019, Vitaly Kuznetsov wrote:
> 
> > There is no particular reason to not enable TSC page clocksource
> > on 32-bit. mul_u64_u64_shr() is available and despite the increased
> > computational complexity (compared to 64bit) TSC page is still a huge
> > win compared to MSR-based clocksource.
> > 
> > In-kernel reads:
> >   MSR based clocksource: 3361 cycles
> >   TSC page clocksource: 49 cycles
> > 
> > Reads from userspace (unilizing vDSO in case of TSC page):
> >   MSR based clocksource: 5664 cycles
> >   TSC page clocksource: 131 cycles
> > 
> > Enabling TSC page on 32bits allows us to get rid of CONFIG_HYPERV_TSCPAGE
> 
> s/allows us/allows/
> 
> > as it is now not any different from CONFIG_HYPERV_TIMER.
> > 
> > Signed-off-by: Vitaly Kuznetsov <vkuznets@redhat.com>
> > ---
> >  arch/x86/include/asm/vdso/gettimeofday.h |  6 +++---
> >  drivers/clocksource/hyperv_timer.c       | 11 -----------
> >  drivers/hv/Kconfig                       |  3 ---
> >  include/clocksource/hyperv_timer.h       |  6 ++----
> >  4 files changed, 5 insertions(+), 21 deletions(-)
> 
> Really nice cleanup as a side effect of adding functionality.

That said, could you please rebase that on

  git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip.git timers/core

as I just applied the TSC page patches there and this conflicts left and
right.

Thanks,

	tglx

Re: [PATCH] x86/hyper-v: enable TSC page clocksource on 32bit

[Vitaly Kuznetsov]

Thomas Gleixner <tglx@linutronix.de> writes:

> On Wed, 21 Aug 2019, Thomas Gleixner wrote:
>
>> On Wed, 21 Aug 2019, Vitaly Kuznetsov wrote:
>> 
>> > There is no particular reason to not enable TSC page clocksource
>> > on 32-bit. mul_u64_u64_shr() is available and despite the increased
>> > computational complexity (compared to 64bit) TSC page is still a huge
>> > win compared to MSR-based clocksource.
>> > 
>> > In-kernel reads:
>> >   MSR based clocksource: 3361 cycles
>> >   TSC page clocksource: 49 cycles
>> > 
>> > Reads from userspace (unilizing vDSO in case of TSC page):
>> >   MSR based clocksource: 5664 cycles
>> >   TSC page clocksource: 131 cycles
>> > 
>> > Enabling TSC page on 32bits allows us to get rid of CONFIG_HYPERV_TSCPAGE
>> 
>> s/allows us/allows/
>> 
>> > as it is now not any different from CONFIG_HYPERV_TIMER.
>> > 
>> > Signed-off-by: Vitaly Kuznetsov <vkuznets@redhat.com>
>> > ---
>> >  arch/x86/include/asm/vdso/gettimeofday.h |  6 +++---
>> >  drivers/clocksource/hyperv_timer.c       | 11 -----------
>> >  drivers/hv/Kconfig                       |  3 ---
>> >  include/clocksource/hyperv_timer.h       |  6 ++----
>> >  4 files changed, 5 insertions(+), 21 deletions(-)
>> 
>> Really nice cleanup as a side effect of adding functionality.
>
> That said, could you please rebase that on
>
>   git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip.git timers/core
>
> as I just applied the TSC page patches there and this conflicts left and
> right.

Sure, v2 is coming!

-- 
Vitaly