Hello Sebastian, On 6/15/22 13:38, 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
Since starting the threads represents some work that can disturb the threads, shouldn't the main thread be migrated to the 'mainaffinity' mask early as it is right now ? I think it would be better to: 1. Save the initial mask of the main thread somewhere 2. Set the affinity of the main thread 3. Use the initial mask when setting the affinity of the threads Regards, Pierre
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)
