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

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Message-ID: <20200811081111.GA31614@oc3871087118.ibm.com>
Date:   Tue, 11 Aug 2020 10:11:11 +0200
From:   Alexander Gordeev <agordeev@...ux.ibm.com>
To:     Namhyung Kim <namhyung@...nel.org>
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

On Tue, Aug 11, 2020 at 04:26:50PM +0900, Namhyung Kim wrote:
> 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.

Well, the whole approach to memory allocation is rather relaxed
troughout the code. I.e cpumasks do not get deallocated (*),
strdup() return values are not checked etc.

If it worth fixing all that then it would be a separate effort,
as far as I am concerned.

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