Re: [PATCH v2 01/12] sched/isolation: Separate housekeeping types in enum hk_type

[Waiman Long <longman@redhat.com>]

On 4/13/26 3:43 AM, Qiliang Yuan wrote:
> Most kernel noise types (TICK, TIMER, RCU, etc.) are currently aliased
> to a single HK_TYPE_KERNEL_NOISE enum value. This prevents fine-grained
> runtime isolation control as all masks are forced to be identical.
>
> Un-alias service-specific housekeeping types in enum hk_type. This
> separation provides the necessary granularity for DHM subsystems to
> subscribe to and maintain independent affinity masks.

Usually, if we want to run a latency sensitive workload like DPDK, we 
try to minimize all sorts of kernel noises or interference as much as 
possible. Do you have a good use case where it is advantageous to remove 
some types of kernel noises from a given set of CPUs but not the others?

Cheers,
Longman

> Signed-off-by: Qiliang Yuan <realwujing@gmail.com>
> ---
>   include/linux/sched/isolation.h | 20 ++++++++------------
>   kernel/sched/isolation.c        | 10 +++++++++-
>   2 files changed, 17 insertions(+), 13 deletions(-)
>
> diff --git a/include/linux/sched/isolation.h b/include/linux/sched/isolation.h
> index dc3975ff1b2e1..b9a041247565c 100644
> --- a/include/linux/sched/isolation.h
> +++ b/include/linux/sched/isolation.h
> @@ -17,21 +17,17 @@ enum hk_type {
>   	/* Inverse of boot-time isolcpus=managed_irq argument */
>   	HK_TYPE_MANAGED_IRQ,
>   	/* Inverse of boot-time nohz_full= or isolcpus=nohz arguments */
> -	HK_TYPE_KERNEL_NOISE,
> +	HK_TYPE_TICK,
> +	HK_TYPE_TIMER,
> +	HK_TYPE_RCU,
> +	HK_TYPE_MISC,
> +	HK_TYPE_WQ,
> +	HK_TYPE_KTHREAD,
>   	HK_TYPE_MAX,
> -
> -	/*
> -	 * The following housekeeping types are only set by the nohz_full
> -	 * boot commandline option. So they can share the same value.
> -	 */
> -	HK_TYPE_TICK    = HK_TYPE_KERNEL_NOISE,
> -	HK_TYPE_TIMER   = HK_TYPE_KERNEL_NOISE,
> -	HK_TYPE_RCU     = HK_TYPE_KERNEL_NOISE,
> -	HK_TYPE_MISC    = HK_TYPE_KERNEL_NOISE,
> -	HK_TYPE_WQ      = HK_TYPE_KERNEL_NOISE,
> -	HK_TYPE_KTHREAD = HK_TYPE_KERNEL_NOISE
>   };
>   
> +#define HK_TYPE_KERNEL_NOISE HK_TYPE_TICK
> +
>   #ifdef CONFIG_CPU_ISOLATION
>   DECLARE_STATIC_KEY_FALSE(housekeeping_overridden);
>   extern int housekeeping_any_cpu(enum hk_type type);
> diff --git a/kernel/sched/isolation.c b/kernel/sched/isolation.c
> index ef152d401fe20..e05ed5118e651 100644
> --- a/kernel/sched/isolation.c
> +++ b/kernel/sched/isolation.c
> @@ -15,9 +15,17 @@ enum hk_flags {
>   	HK_FLAG_DOMAIN_BOOT	= BIT(HK_TYPE_DOMAIN_BOOT),
>   	HK_FLAG_DOMAIN		= BIT(HK_TYPE_DOMAIN),
>   	HK_FLAG_MANAGED_IRQ	= BIT(HK_TYPE_MANAGED_IRQ),
> -	HK_FLAG_KERNEL_NOISE	= BIT(HK_TYPE_KERNEL_NOISE),
> +	HK_FLAG_TICK		= BIT(HK_TYPE_TICK),
> +	HK_FLAG_TIMER		= BIT(HK_TYPE_TIMER),
> +	HK_FLAG_RCU		= BIT(HK_TYPE_RCU),
> +	HK_FLAG_MISC		= BIT(HK_TYPE_MISC),
> +	HK_FLAG_WQ		= BIT(HK_TYPE_WQ),
> +	HK_FLAG_KTHREAD		= BIT(HK_TYPE_KTHREAD),
>   };
>   
> +#define HK_FLAG_KERNEL_NOISE (HK_FLAG_TICK | HK_FLAG_TIMER | HK_FLAG_RCU | \
> +			      HK_FLAG_MISC | HK_FLAG_WQ | HK_FLAG_KTHREAD)
> +
>   DEFINE_STATIC_KEY_FALSE(housekeeping_overridden);
>   EXPORT_SYMBOL_GPL(housekeeping_overridden);
>   
>