Subject: Re: [PATCH 4/4] powerpc/pseries: Implement CONFIG_PARAVIRT_TIME_ACCOUNTING

From: Fabiano Rosas <[email-masked]>
Date: Fri, 27 May 2022 17:47:14 -0300

Nicholas Piggin <[email-masked]> writes:

> CONFIG_VIRT_CPU_ACCOUNTING_GEN under pseries does not implement
> stolen time accounting. Implement it with the paravirt time
> accounting option.
>
> Signed-off-by: Nicholas Piggin <[email-masked]>
> ---
>  .../admin-guide/kernel-parameters.txt         |  6 +++---
>  arch/powerpc/include/asm/paravirt.h           | 12 ++++++++++++
>  arch/powerpc/platforms/pseries/Kconfig        |  8 ++++++++
>  arch/powerpc/platforms/pseries/lpar.c         | 11 +++++++++++
>  arch/powerpc/platforms/pseries/setup.c        | 19 +++++++++++++++++++
>  5 files changed, 53 insertions(+), 3 deletions(-)
>
> diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
> index 3f1cc5e317ed..855fc7b02261 100644
> --- a/Documentation/admin-guide/kernel-parameters.txt
> +++ b/Documentation/admin-guide/kernel-parameters.txt
> @@ -3604,9 +3604,9 @@
>  			[X86,PV_OPS] Disable paravirtualized VMware scheduler
>  			clock and use the default one.
>
> -	no-steal-acc	[X86,PV_OPS,ARM64] Disable paravirtualized steal time
> -			accounting. steal time is computed, but won't
> -			influence scheduler behaviour
> +	no-steal-acc	[X86,PV_OPS,ARM64,PPC/PSERIES] Disable paravirtualized
> +			steal time accounting. steal time is computed, but
> +			won't influence scheduler behaviour
>
>  	nolapic		[X86-32,APIC] Do not enable or use the local APIC.
>
> diff --git a/arch/powerpc/include/asm/paravirt.h b/arch/powerpc/include/asm/paravirt.h
> index eb7df559ae74..f5ba1a3c41f8 100644
> --- a/arch/powerpc/include/asm/paravirt.h
> +++ b/arch/powerpc/include/asm/paravirt.h
> @@ -21,6 +21,18 @@ static inline bool is_shared_processor(void)
>  	return static_branch_unlikely(&shared_processor);
>  }
>
> +#ifdef CONFIG_PARAVIRT_TIME_ACCOUNTING
> +extern struct static_key paravirt_steal_enabled;
> +extern struct static_key paravirt_steal_rq_enabled;
> +
> +u64 pseries_paravirt_steal_clock(int cpu);
> +
> +static inline u64 paravirt_steal_clock(int cpu)
> +{
> +	return pseries_paravirt_steal_clock(cpu);
> +}
> +#endif
> +
>  /* If bit 0 is set, the cpu has been ceded, conferred, or preempted */
>  static inline u32 yield_count_of(int cpu)
>  {
> diff --git a/arch/powerpc/platforms/pseries/Kconfig b/arch/powerpc/platforms/pseries/Kconfig
> index f7fd91d153a4..d4306ebdca5e 100644
> --- a/arch/powerpc/platforms/pseries/Kconfig
> +++ b/arch/powerpc/platforms/pseries/Kconfig
> @@ -24,13 +24,21 @@ config PPC_PSERIES
>  	select SWIOTLB
>  	default y
>
> +config PARAVIRT
> +	bool
> +

In file included from ../kernel/sched/build_utility.c:53:
../kernel/sched/sched.h:87:11: fatal error: asm/paravirt_api_clock.h: No such file or directory
   87 | # include <asm/paravirt_api_clock.h>

$ find . -name paravirt_api_clock.h
./arch/arm64/include/asm/paravirt_api_clock.h
./arch/x86/include/asm/paravirt_api_clock.h
./arch/arm/include/asm/paravirt_api_clock.h

>  config PARAVIRT_SPINLOCKS
>  	bool
>
> +config PARAVIRT_TIME_ACCOUNTING
> +	select PARAVIRT
> +	bool
> +
>  config PPC_SPLPAR
>  	bool "Support for shared-processor logical partitions"
>  	depends on PPC_PSERIES
>  	select PARAVIRT_SPINLOCKS if PPC_QUEUED_SPINLOCKS
> +	select PARAVIRT_TIME_ACCOUNTING if VIRT_CPU_ACCOUNTING_GEN
>  	default y
>  	help
>  	  Enabling this option will make the kernel run more efficiently