linux-kernel - Re: [PATCH v2 net] ipvs: Fix estimator kthreads preferred affinity

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Message-ID: <2d915ef6-46eb-7487-f235-6b6688e68c58@ssi.bg>
Date: Wed, 30 Jul 2025 13:28:16 +0300 (EEST)
From: Julian Anastasov <ja@....bg>
To: Frederic Weisbecker <frederic@...nel.org>
cc: LKML <linux-kernel@...r.kernel.org>,
        "David S. Miller" <davem@...emloft.net>,
        David Ahern <dsahern@...nel.org>, Simon Horman <horms@...ge.net.au>,
        Eric Dumazet <edumazet@...gle.com>, Jakub Kicinski <kuba@...nel.org>,
        Paolo Abeni <pabeni@...hat.com>,
        Pablo Neira Ayuso <pablo@...filter.org>,
        Jozsef Kadlecsik <kadlec@...filter.org>, netdev@...r.kernel.org,
        lvs-devel@...r.kernel.org, netfilter-devel@...r.kernel.org,
        coreteam@...filter.org
Subject: Re: [PATCH v2 net] ipvs: Fix estimator kthreads preferred affinity


	Hello,

On Tue, 29 Jul 2025, Frederic Weisbecker wrote:

> The estimator kthreads' affinity are defined by sysctl overwritten
> preferences and applied through a plain call to the scheduler's affinity
> API.
> 
> However since the introduction of managed kthreads preferred affinity,
> such a practice shortcuts the kthreads core code which eventually
> overwrites the target to the default unbound affinity.
> 
> Fix this with using the appropriate kthread's API.
> 
> Fixes: d1a89197589c ("kthread: Default affine kthread to its preferred NUMA node")
> Signed-off-by: Frederic Weisbecker <frederic@...nel.org>

	Looks good to me for the nf tree, thanks!

Acked-by: Julian Anastasov <ja@....bg>

> ---
>  include/net/ip_vs.h            | 13 +++++++++++++
>  kernel/kthread.c               |  1 +
>  net/netfilter/ipvs/ip_vs_est.c |  3 ++-
>  3 files changed, 16 insertions(+), 1 deletion(-)
> 
> diff --git a/include/net/ip_vs.h b/include/net/ip_vs.h
> index ff406ef4fd4a..29a36709e7f3 100644
> --- a/include/net/ip_vs.h
> +++ b/include/net/ip_vs.h
> @@ -1163,6 +1163,14 @@ static inline const struct cpumask *sysctl_est_cpulist(struct netns_ipvs *ipvs)
>  		return housekeeping_cpumask(HK_TYPE_KTHREAD);
>  }
>  
> +static inline const struct cpumask *sysctl_est_preferred_cpulist(struct netns_ipvs *ipvs)
> +{
> +	if (ipvs->est_cpulist_valid)
> +		return ipvs->sysctl_est_cpulist;
> +	else
> +		return NULL;
> +}
> +
>  static inline int sysctl_est_nice(struct netns_ipvs *ipvs)
>  {
>  	return ipvs->sysctl_est_nice;
> @@ -1270,6 +1278,11 @@ static inline const struct cpumask *sysctl_est_cpulist(struct netns_ipvs *ipvs)
>  	return housekeeping_cpumask(HK_TYPE_KTHREAD);
>  }
>  
> +static inline const struct cpumask *sysctl_est_preferred_cpulist(struct netns_ipvs *ipvs)
> +{
> +	return NULL;
> +}
> +
>  static inline int sysctl_est_nice(struct netns_ipvs *ipvs)
>  {
>  	return IPVS_EST_NICE;
> diff --git a/kernel/kthread.c b/kernel/kthread.c
> index 85e29b250107..adf06196b844 100644
> --- a/kernel/kthread.c
> +++ b/kernel/kthread.c
> @@ -899,6 +899,7 @@ int kthread_affine_preferred(struct task_struct *p, const struct cpumask *mask)
>  
>  	return ret;
>  }
> +EXPORT_SYMBOL_GPL(kthread_affine_preferred);
>  
>  static int kthreads_update_affinity(bool force)
>  {
> diff --git a/net/netfilter/ipvs/ip_vs_est.c b/net/netfilter/ipvs/ip_vs_est.c
> index f821ad2e19b3..15049b826732 100644
> --- a/net/netfilter/ipvs/ip_vs_est.c
> +++ b/net/netfilter/ipvs/ip_vs_est.c
> @@ -265,7 +265,8 @@ int ip_vs_est_kthread_start(struct netns_ipvs *ipvs,
>  	}
>  
>  	set_user_nice(kd->task, sysctl_est_nice(ipvs));
> -	set_cpus_allowed_ptr(kd->task, sysctl_est_cpulist(ipvs));
> +	if (sysctl_est_preferred_cpulist(ipvs))
> +		kthread_affine_preferred(kd->task, sysctl_est_preferred_cpulist(ipvs));
>  
>  	pr_info("starting estimator thread %d...\n", kd->id);
>  	wake_up_process(kd->task);
> -- 
> 2.48.1

Regards

--
Julian Anastasov <ja@....bg>