[PATCH v2 net] ipvs: Fix estimator kthreads preferred affinity

[PATCH v2 net] ipvs: Fix estimator kthreads preferred affinity

[Frederic Weisbecker]

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@kernel.org>
---
 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

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

[Julian Anastasov]

	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@kernel.org>

	Looks good to me for the nf tree, thanks!

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

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

[Pablo Neira Ayuso]

On Wed, Jul 30, 2025 at 01:28:16PM +0300, Julian Anastasov wrote:
> 
> 	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@kernel.org>
> 
> 	Looks good to me for the nf tree, thanks!
> 
> Acked-by: Julian Anastasov <ja@ssi.bg>

For the record: Apologies, I will include this patch in the next pull request.