linux-kernel - Re: [PATCH RESEND v3] sched/isolation: Prefer housekeeping cpu in local node

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Date:   Fri, 28 Jun 2019 15:19:17 +0800
From:   Wanpeng Li <kernellwp@...il.com>
To:     Srikar Dronamraju <srikar@...ux.vnet.ibm.com>
Cc:     LKML <linux-kernel@...r.kernel.org>,
        Ingo Molnar <mingo@...nel.org>,
        Peter Zijlstra <peterz@...radead.org>,
        Ingo Molnar <mingo@...hat.com>,
        Frederic Weisbecker <frederic@...nel.org>,
        Thomas Gleixner <tglx@...utronix.de>
Subject: Re: [PATCH RESEND v3] sched/isolation: Prefer housekeeping cpu in
 local node

Hi Srikar,
On Fri, 28 Jun 2019 at 14:58, Srikar Dronamraju
<srikar@...ux.vnet.ibm.com> wrote:
>
> * Wanpeng Li <kernellwp@...il.com> [2019-06-28 08:43:13]:
>
>
> >
> > +/*
> > + * sched_numa_find_closest() - given the NUMA topology, find the cpu
> > + *                             closest to @cpu from @cpumask.
> > + * cpumask: cpumask to find a cpu from
> > + * cpu: cpu to be close to
> > + *
> > + * returns: cpu, or >= nr_cpu_ids when nothing found (or !NUMA).
>
> One nit:
> I dont see sched_numa_find_closest returning anything greater than
> nr_cpu_ids. So 's/>= //' for the above comment.
>
> > + */
> > +int sched_numa_find_closest(const struct cpumask *cpus, int cpu)
> > +{
> > +#ifdef CONFIG_NUMA
> > +     int i, j = cpu_to_node(cpu);
> > +
> > +     for (i = 0; i < sched_domains_numa_levels; i++) {
> > +             cpu = cpumask_any_and(cpus, sched_domains_numa_masks[i][j]);
> > +             if (cpu < nr_cpu_ids)
> > +                     return cpu;
> > +     }
> > +#endif
> > +     return nr_cpu_ids;
> > +}
> > +
>
> Should we have a static function for sched_numa_find_closest instead of
> having #ifdef in the function?
>
> >  static int __sdt_alloc(const struct cpumask *cpu_map)
> >  {
> >       struct sched_domain_topology_level *tl;

So, how about add this?

diff --git a/kernel/sched/sched.h b/kernel/sched/sched.h
index a7e7d8c..5f2b262 100644
--- a/kernel/sched/sched.h
+++ b/kernel/sched/sched.h
@@ -1225,13 +1225,17 @@ enum numa_topology_type {
 extern void sched_init_numa(void);
 extern void sched_domains_numa_masks_set(unsigned int cpu);
 extern void sched_domains_numa_masks_clear(unsigned int cpu);
+extern int sched_numa_find_closest(const struct cpumask *cpus, int cpu);
 #else
 static inline void sched_init_numa(void) { }
 static inline void sched_domains_numa_masks_set(unsigned int cpu) { }
 static inline void sched_domains_numa_masks_clear(unsigned int cpu) { }
+static inline int sched_numa_find_closest(const struct cpumask *cpus, int cpu)
+{
+    return nr_cpu_ids;
+}
 #endif

-extern int sched_numa_find_closest(const struct cpumask *cpus, int cpu);

 #ifdef CONFIG_NUMA_BALANCING
 /* The regions in numa_faults array from task_struct */
diff --git a/kernel/sched/topology.c b/kernel/sched/topology.c
index 72731ed..9372c18 100644
--- a/kernel/sched/topology.c
+++ b/kernel/sched/topology.c
@@ -1734,19 +1734,16 @@ void sched_domains_numa_masks_clear(unsigned int cpu)
     }
 }

-#endif /* CONFIG_NUMA */
-
 /*
  * sched_numa_find_closest() - given the NUMA topology, find the cpu
  *                             closest to @cpu from @cpumask.
  * cpumask: cpumask to find a cpu from
  * cpu: cpu to be close to
  *
- * returns: cpu, or >= nr_cpu_ids when nothing found (or !NUMA).
+ * returns: cpu, or nr_cpu_ids when nothing found.
  */
 int sched_numa_find_closest(const struct cpumask *cpus, int cpu)
 {
-#ifdef CONFIG_NUMA
     int i, j = cpu_to_node(cpu);

     for (i = 0; i < sched_domains_numa_levels; i++) {
@@ -1754,10 +1751,11 @@ int sched_numa_find_closest(const struct
cpumask *cpus, int cpu)
         if (cpu < nr_cpu_ids)
             return cpu;
     }
-#endif
     return nr_cpu_ids;
 }

+#endif /* CONFIG_NUMA */
+
 static int __sdt_alloc(const struct cpumask *cpu_map)
 {
     struct sched_domain_topology_level *tl;