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selftests: ublk: set CPU affinity before thread initialization

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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 <ming.lei@redhat.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
This commit is contained in:
Ming Lei
2025-11-01 21:31:19 +08:00
committed by Jens Axboe
parent c28ba6b6c5
commit 0123bb91f4
1 changed files with 10 additions and 4 deletions
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14
tools/testing/selftests/ublk/kublk.c
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@@ -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",