On Thu, 12 Jan 2023, Sebastian Andrzej Siewior wrote:
> numa_num_task_cpus() returns here > 100 CPUs while the system has only
> 32 populated. The BIOS assumes that I can probably use larger CPUs (with
> more cores) on the socket so the number of "configured CPUs" is rather
> high.
> For default configuration, only with the -S option, it makes sense to
> use the current affinity instead looking at the number of possible CPUs
> which could be brought online. It still depends on the affinity of the
> created threads if the additional CPUs can be used. In a container setup
> this may not be the case.
>
> Use sched_getaffinity() to figure out the number of possible CPUs.
>
> Signed-off-by: Sebastian Andrzej Siewior <bigeasy@xxxxxxxxxxxxx>
> ---
> src/lib/rt-numa.c | 11 ++++++++++-
> 1 file changed, 10 insertions(+), 1 deletion(-)
>
> diff --git a/src/lib/rt-numa.c b/src/lib/rt-numa.c
> index 3eead80c3b2b3..1b09cff8d9485 100644
> --- a/src/lib/rt-numa.c
> +++ b/src/lib/rt-numa.c
> @@ -35,10 +35,19 @@ int numa_initialize(void)
>
> int get_available_cpus(struct bitmask *cpumask)
> {
> + cpu_set_t cpuset;
> + int ret;
> +
> if (cpumask)
> return numa_bitmask_weight(cpumask);
>
> - return numa_num_task_cpus();
> + CPU_ZERO(&cpuset);
> +
> + ret = sched_getaffinity(0, sizeof(cpu_set_t), &cpuset);
> + if (ret < 0)
> + fatal("sched_getaffinity failed: %m\n");
> +
> + return CPU_COUNT(&cpuset);
> }
>
> int cpu_for_thread_sp(int thread_num, int max_cpus, struct bitmask *cpumask)
> --
> 2.39.0
>
In cyclictest we have
if (num_threads == -1)
num_threads = get_available_cpus(affinity_mask);
But the num_threads can be set to -1 in OPT_THREADS too,
not just for OPT_SMP
John Kacur
