* Mateusz Guzik <mjguzik@xxxxxxxxx> [250206 11:44]:
> I fixed fat-fingering and touchedup some commit messages. git diff
> between the old and new branch does not show any code changes.
Thanks for doing these changes.
Acked-by: Liam R. Howlett <Liam.Howlett@xxxxxxxxxx>
>
> hopefully we will be done here after this iteration 8->
>
> old cover letter:
>
> The clone side contends against exit side in a way which avoidably
> exacerbates the problem by the latter waiting on locks held by the
> former while holding the tasklist_lock.
>
> Whacking this for both add_device_randomness and pids allocation gives
> me a 15% speed up for thread creation/destruction in a 24-core vm.
>
> The random patch is worth about 4%.
>
> The new bottleneck is pidmap_lock itself, with the biggest problem being
> the allocation itself taking the lock *twice*.
>
> Bench (plop into will-it-scale):
> $ cat tests/threadspawn1.c
>
> char *testcase_description = "Thread creation and teardown";
>
> static void *worker(void *arg)
> {
> return (NULL);
> }
>
> void testcase(unsigned long long *iterations, unsigned long nr)
> {
> pthread_t thread;
> int error;
>
> while (1) {
> error = pthread_create(&thread, NULL, worker, NULL);
> assert(error == 0);
> error = pthread_join(thread, NULL);
> assert(error == 0);
> (*iterations)++;
> }
> }
>
> v6:
> - expand on the commit message in 3/5 pid: sprinkle tasklist_lock asserts
> - move fat-fingered free_pids call to the right patch
>
> v5:
> - whack scripts/selinux/genheaders/genheaders which accidentally got in
> - rebased on next-20250205
>
> v4:
> - justify moving get_pid in the commit message with a one-liner
> - drop the tty unref patch -- it is completely optional and Oleg has his
> own variant
> - add the ACK by Oleg
>
> v3:
> - keep procfs flush where it was, instead hoist get_pid outside of the
> lock
> - make detach_pid et al accept an array argument of pids to populate
> - sprinkle asserts
> - drop irq trips around pidmap_lock
> - move tty unref outside of tasklist_lock
>
>
>
> Mateusz Guzik (5):
> exit: perform add_device_randomness() without tasklist_lock
> exit: hoist get_pid() in release_task() outside of tasklist_lock
> pid: sprinkle tasklist_lock asserts
> pid: perform free_pid() calls outside of tasklist_lock
> pid: drop irq disablement around pidmap_lock
>
> include/linux/pid.h | 7 ++--
> kernel/exit.c | 36 +++++++++++++-------
> kernel/pid.c | 82 +++++++++++++++++++++++++--------------------
> kernel/sys.c | 14 +++++---
> 4 files changed, 82 insertions(+), 57 deletions(-)
>
> --
> 2.43.0
>
