[PATCH 2/4] tickless idle cpu: Skip ticks when CPU is idle

[Kumar Gala]

On Apr 7, 2006, at 1:31 AM, Srivatsa Vaddagiri wrote:

> This is the core patch which skips ticks when a CPU is idle.
> Should work on pSeries, pmac and maple machines.
>
> The patch is against 2.6.17-rc1-mm1 and has been tested on a 16-way  
> (with SMT)
> Power5 box (p570).
>
> Signed-off-by: Srivatsa Vaddagiri <vatsa at in.ibm.com>
>
> ---
>
>  linux-2.6.17-rc1-root/arch/powerpc/Kconfig                   |    6
>  linux-2.6.17-rc1-root/arch/powerpc/kernel/idle_power4.S      |    3
>  linux-2.6.17-rc1-root/arch/powerpc/kernel/irq.c              |    3
>  linux-2.6.17-rc1-root/arch/powerpc/kernel/time.c             |   
> 150 ++++++++---
>  linux-2.6.17-rc1-root/arch/powerpc/kernel/traps.c            |    1
>  linux-2.6.17-rc1-root/arch/powerpc/platforms/pseries/setup.c |    6
>  linux-2.6.17-rc1-root/include/asm-powerpc/time.h             |    8
>  7 files changed, 147 insertions(+), 30 deletions(-)
>

[snip]

> diff -puN arch/powerpc/Kconfig~no_idle_hz arch/powerpc/Kconfig
> --- linux-2.6.17-rc1/arch/powerpc/Kconfig~no_idle_hz	2006-04-07  
> 04:14:39.000000000 +0530
> +++ linux-2.6.17-rc1-root/arch/powerpc/Kconfig	2006-04-07  
> 04:14:58.000000000 +0530
> @@ -593,6 +593,12 @@ config HOTPLUG_CPU
>
>  	  Say N if you are unsure.
>
> +config NO_IDLE_HZ
> +	depends on EXPERIMENTAL && (PPC_PSERIES || PPC_PMAC || PPC_MAPLE)
> +	bool "Switch off timer ticks on idle CPUs"
> +	help
> +	  Switches the HZ timer interrupts off when a CPU is idle.
> +

any reason not to provide this for all 6xx class processors?

>  config KEXEC
>  	bool "kexec system call (EXPERIMENTAL)"
>  	depends on PPC_MULTIPLATFORM && EXPERIMENTAL