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%.
nothing blew up with lockdep, lightly tested so far
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)++;
}
}
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 (6):
exit: perform add_device_randomness() without tasklist_lock
exit: hoist get_pid() in release_task() outside of tasklist_lock
exit: postpone tty_kref_put() until after tasklist_lock is dropped
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 | 45 +++++++++++++++----------
kernel/pid.c | 82 +++++++++++++++++++++++++--------------------
kernel/sys.c | 14 +++++---
4 files changed, 86 insertions(+), 62 deletions(-)
--
2.43.0
