On Wed, 15 Jun 2022, Sebastian Andrzej Siewior wrote:
> Assuming the current affinity mask of the task is 0x31 (CPUs 0, 4, 5).
> Starting cyclictest with '-S' option will fork the following threads:
> - monitor, mask 0x31
> - measure thread 1, mask 0x01
> - measure thread 2, mask 0x10
> - measure thread 3, mask 0x20
>
> works as expected. Using the options '-S --mainaffinity=0' leads to:
> - monitor, mask 0x01
> - measure thread 1, mask 0x01
> - measure thread 2, mask 0x01
> - measure thread 3, mask 0x01
>
> because the mask of the main thread has been reset early to 0x01 and
> does not allow a CPU mask outside of this mask while setting the
> affinity for the new threads.
>
> Delay setting the affinity of the main/ monitor thread after the
> measuring threads have been deployed. This leads to the following
> state:
> - monitor, mask 0x01
> - measure thread 1, mask 0x01
> - measure thread 2, mask 0x10
> - measure thread 3, mask 0x20
>
> Signed-off-by: Sebastian Andrzej Savior <bigeasy@xxxxxxxxxxxxx>
> ---
> src/cyclictest/cyclictest.c | 9 +++++----
> 1 file changed, 5 insertions(+), 4 deletions(-)
>
> diff --git a/src/cyclictest/cyclictest.c b/src/cyclictest/cyclictest.c
> index be8285a072b4e..cbf8d00293ec6 100644
> --- a/src/cyclictest/cyclictest.c
> +++ b/src/cyclictest/cyclictest.c
> @@ -1816,10 +1816,7 @@ int main(int argc, char **argv)
> printf("Online CPUs = %d\n", online_cpus);
> }
>
> - /* Restrict the main pid to the affinity specified by the user */
> - if (main_affinity_mask != NULL) {
> - set_main_thread_affinity(main_affinity_mask);
> - } else if (affinity_mask != NULL) {
> + if (affinity_mask != NULL) {
> set_main_thread_affinity(affinity_mask);
> if (verbose)
> printf("Using %u cpus.\n",
> @@ -2094,6 +2091,10 @@ int main(int argc, char **argv)
> fatal("failed to create thread %d: %s\n", i, strerror(status));
>
> }
> + /* Restrict the main pid to the affinity specified by the user */
> + if (main_affinity_mask != NULL)
> + set_main_thread_affinity(main_affinity_mask);
> +
> if (use_fifo) {
> status = pthread_create(&fifo_threadid, NULL, fifothread, NULL);
> if (status)
> --
> 2.36.1
>
>
Signed-off-by: John Kacur <jkacur@xxxxxxxxxx>
