linux-kernel - Re: [RFC 2/6] sched: add a new SD SHARE_POWERLINE flag for sched

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Message-ID: <5088066D.7000907@ti.com>
Date:	Wed, 24 Oct 2012 20:47:01 +0530
From:	Santosh Shilimkar <santosh.shilimkar@...com>
To:	Vincent Guittot <vincent.guittot@...aro.org>
CC:	<linux-kernel@...r.kernel.org>,
	<linux-arm-kernel@...ts.infradead.org>,
	<linaro-dev@...ts.linaro.org>, <peterz@...radead.org>,
	<mingo@...hat.com>, <pjt@...gle.com>, <linux@....linux.org.uk>
Subject: Re: [RFC 2/6] sched: add a new SD SHARE_POWERLINE flag for sched_domain

Vincent,

Few comments/questions.

On Sunday 07 October 2012 01:13 PM, Vincent Guittot wrote:
> This new flag SD SHARE_POWERLINE reflects the sharing of the power rail
> between the members of a domain. As this is the current assumption of the
> scheduler, the flag is added to all sched_domain
>
> Signed-off-by: Vincent Guittot <vincent.guittot@...aro.org>
> ---
>   arch/ia64/include/asm/topology.h |    1 +
>   arch/tile/include/asm/topology.h |    1 +
>   include/linux/sched.h            |    1 +
>   include/linux/topology.h         |    3 +++
>   kernel/sched/core.c              |    5 +++++
>   5 files changed, 11 insertions(+)
>
> diff --git a/arch/ia64/include/asm/topology.h b/arch/ia64/include/asm/topology.h
> index a2496e4..065c720 100644
> --- a/arch/ia64/include/asm/topology.h
> +++ b/arch/ia64/include/asm/topology.h
> @@ -65,6 +65,7 @@ void build_cpu_to_node_map(void);
>   				| SD_BALANCE_EXEC	\
>   				| SD_BALANCE_FORK	\
>   				| SD_WAKE_AFFINE,	\
> +				| arch_sd_share_power_line()		\
>   	.last_balance		= jiffies,		\
>   	.balance_interval	= 1,			\
>   	.nr_balance_failed	= 0,			\
> diff --git a/arch/tile/include/asm/topology.h b/arch/tile/include/asm/topology.h
> index 7a7ce39..d39ed0b 100644
> --- a/arch/tile/include/asm/topology.h
> +++ b/arch/tile/include/asm/topology.h
> @@ -72,6 +72,7 @@ static inline const struct cpumask *cpumask_of_node(int node)
>   				| 0*SD_PREFER_LOCAL			\
>   				| 0*SD_SHARE_CPUPOWER			\
>   				| 0*SD_SHARE_PKG_RESOURCES		\
> +				| arch_sd_share_power_line()		\
>   				| 0*SD_SERIALIZE			\
>   				,					\
>   	.last_balance		= jiffies,				\
> diff --git a/include/linux/sched.h b/include/linux/sched.h
> index 4786b20..74f2daf 100644
> --- a/include/linux/sched.h
> +++ b/include/linux/sched.h
> @@ -862,6 +862,7 @@ enum cpu_idle_type {
>   #define SD_WAKE_AFFINE		0x0020	/* Wake task to waking CPU */
>   #define SD_PREFER_LOCAL		0x0040  /* Prefer to keep tasks local to this domain */
>   #define SD_SHARE_CPUPOWER	0x0080	/* Domain members share cpu power */
> +#define SD_SHARE_POWERLINE	0x0100	/* Domain members share power domain */
If you ignore the current use of SD_SHARE_CPUPOWER, isn't the meaning of
CPUPOWER and POWERLINE is same here. Just trying to understand the clear
meaning of this new flag. Have you not considered SD_SHARE_CPUPOWER
because it is being used for cpu_power and needs at least minimum two
domains ? SD_PACKING would have been probably more appropriate based
on the way it is being used in further series.

Regards
Santosh

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