linux-kernel - Re: [PATCH v2 1/3] perf bench numa: use numa_node_to

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Date:   Tue, 11 Aug 2020 16:26:50 +0900
From:   Namhyung Kim <namhyung@...nel.org>
To:     Alexander Gordeev <agordeev@...ux.ibm.com>
Cc:     linux-kernel <linux-kernel@...r.kernel.org>,
        Satheesh Rajendran <sathnaga@...ux.vnet.ibm.com>,
        Srikar Dronamraju <srikar@...ux.vnet.ibm.com>,
        "Naveen N. Rao" <naveen.n.rao@...ux.vnet.ibm.com>,
        Balamuruhan S <bala24@...ux.vnet.ibm.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Ingo Molnar <mingo@...hat.com>,
        Arnaldo Carvalho de Melo <acme@...nel.org>,
        Mark Rutland <mark.rutland@....com>,
        Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
        Jiri Olsa <jolsa@...hat.com>
Subject: Re: [PATCH v2 1/3] perf bench numa: use numa_node_to_cpus() to bind
 tasks to nodes

Hello,

On Mon, Aug 10, 2020 at 3:22 PM Alexander Gordeev
<agordeev@...ux.ibm.com> wrote:
>
> It is currently assumed that each node contains at most
> nr_cpus/nr_nodes CPUs and node CPU ranges do not overlap.
> That assumption is generally incorrect as there are archs
> where a CPU number does not depend on to its node number.
>
> This update removes the described assumption by simply calling
> numa_node_to_cpus() interface and using the returned mask for
> binding CPUs to nodes. It also tightens a cpumask allocation
> failure check a bit.
>
> Cc: Satheesh Rajendran <sathnaga@...ux.vnet.ibm.com>
> Cc: Srikar Dronamraju <srikar@...ux.vnet.ibm.com>
> Cc: Naveen N. Rao <naveen.n.rao@...ux.vnet.ibm.com>
> Cc: Balamuruhan S <bala24@...ux.vnet.ibm.com>
> Cc: Peter Zijlstra <peterz@...radead.org>
> Cc: Ingo Molnar <mingo@...hat.com>
> Cc: Arnaldo Carvalho de Melo <acme@...nel.org>
> Cc: Mark Rutland <mark.rutland@....com>
> Cc: Alexander Shishkin <alexander.shishkin@...ux.intel.com>
> Cc: Jiri Olsa <jolsa@...hat.com>
> Cc: Namhyung Kim <namhyung@...nel.org>
> Signed-off-by: Alexander Gordeev <agordeev@...ux.ibm.com>
> ---
>  tools/perf/bench/numa.c | 27 +++++++++++++--------------
>  1 file changed, 13 insertions(+), 14 deletions(-)
>
> diff --git a/tools/perf/bench/numa.c b/tools/perf/bench/numa.c
> index 5797253..23e224e 100644
> --- a/tools/perf/bench/numa.c
> +++ b/tools/perf/bench/numa.c
> @@ -247,12 +247,13 @@ static int is_node_present(int node)
>   */
>  static bool node_has_cpus(int node)
>  {
> -       struct bitmask *cpu = numa_allocate_cpumask();
> +       struct bitmask *cpumask = numa_allocate_cpumask();
>         unsigned int i;
>
> -       if (cpu && !numa_node_to_cpus(node, cpu)) {
> -               for (i = 0; i < cpu->size; i++) {
> -                       if (numa_bitmask_isbitset(cpu, i))
> +       BUG_ON(!cpumask);
> +       if (!numa_node_to_cpus(node, cpumask)) {
> +               for (i = 0; i < cpumask->size; i++) {
> +                       if (numa_bitmask_isbitset(cpumask, i))
>                                 return true;
>                 }
>         }
> @@ -288,14 +289,10 @@ static cpu_set_t bind_to_cpu(int target_cpu)
>
>  static cpu_set_t bind_to_node(int target_node)
>  {
> -       int cpus_per_node = g->p.nr_cpus / nr_numa_nodes();
>         cpu_set_t orig_mask, mask;
>         int cpu;
>         int ret;
>
> -       BUG_ON(cpus_per_node * nr_numa_nodes() != g->p.nr_cpus);
> -       BUG_ON(!cpus_per_node);
> -
>         ret = sched_getaffinity(0, sizeof(orig_mask), &orig_mask);
>         BUG_ON(ret);
>
> @@ -305,13 +302,15 @@ static cpu_set_t bind_to_node(int target_node)
>                 for (cpu = 0; cpu < g->p.nr_cpus; cpu++)
>                         CPU_SET(cpu, &mask);
>         } else {
> -               int cpu_start = (target_node + 0) * cpus_per_node;
> -               int cpu_stop  = (target_node + 1) * cpus_per_node;
> -
> -               BUG_ON(cpu_stop > g->p.nr_cpus);
> +               struct bitmask *cpumask = numa_allocate_cpumask();
>
> -               for (cpu = cpu_start; cpu < cpu_stop; cpu++)
> -                       CPU_SET(cpu, &mask);
> +               BUG_ON(!cpumask);
> +               if (!numa_node_to_cpus(target_node, cpumask)) {
> +                       for (cpu = 0; cpu < (int)cpumask->size; cpu++) {
> +                               if (numa_bitmask_isbitset(cpumask, cpu))
> +                                       CPU_SET(cpu, &mask);
> +                       }
> +               }

It seems you need to call numa_free_cpumask() for both functions.

Thanks
Namhyung

>         }
>
>         ret = sched_setaffinity(0, sizeof(mask), &mask);
> --
> 1.8.3.1
>