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

Waiman Long
2026-04-13T19:26:08Z

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);
>
>