From: Ming Lei Date: Sat, 1 Nov 2025 13:31:19 +0000 (+0800) Subject: selftests: ublk: set CPU affinity before thread initialization X-Git-Tag: v6.19-rc1~168^2~85 X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=0123bb91f464487cc1bbdcc515757dc723496a39;p=thirdparty%2Fkernel%2Flinux.git selftests: ublk: set CPU affinity before thread initialization Move ublk_thread_set_sched_affinity() call before ublk_thread_init() to ensure memory allocations during thread initialization occur on the correct NUMA node. This leverages Linux's first-touch memory policy for better NUMA locality. Also convert ublk_thread_set_sched_affinity() to use pthread_setaffinity_np() instead of sched_setaffinity(), as the pthread API is the proper interface for setting thread affinity in multithreaded programs. Signed-off-by: Ming Lei Signed-off-by: Jens Axboe --- diff --git a/tools/testing/selftests/ublk/kublk.c b/tools/testing/selftests/ublk/kublk.c index 6b8123c12a7ae..062537ab89764 100644 --- a/tools/testing/selftests/ublk/kublk.c +++ b/tools/testing/selftests/ublk/kublk.c @@ -839,7 +839,7 @@ static int ublk_process_io(struct ublk_thread *t) static void ublk_thread_set_sched_affinity(const struct ublk_thread *t, cpu_set_t *cpuset) { - if (sched_setaffinity(0, sizeof(*cpuset), cpuset) < 0) + if (pthread_setaffinity_np(pthread_self(), sizeof(*cpuset), cpuset) < 0) ublk_err("ublk dev %u thread %u set affinity failed", t->dev->dev_info.dev_id, t->idx); } @@ -862,15 +862,21 @@ static void *ublk_io_handler_fn(void *data) t->dev = info->dev; t->idx = info->idx; + /* + * IO perf is sensitive with queue pthread affinity on NUMA machine + * + * Set sched_affinity at beginning, so following allocated memory/pages + * could be CPU/NUMA aware. + */ + if (info->affinity) + ublk_thread_set_sched_affinity(t, info->affinity); + ret = ublk_thread_init(t, info->extra_flags); if (ret) { ublk_err("ublk dev %d thread %u init failed\n", dev_id, t->idx); return NULL; } - /* IO perf is sensitive with queue pthread affinity on NUMA machine*/ - if (info->affinity) - ublk_thread_set_sched_affinity(t, info->affinity); sem_post(info->ready); ublk_dbg(UBLK_DBG_THREAD, "tid %d: ublk dev %d thread %u started\n",