From 9cd80bbb07fcd6d4d037fad4297496d3b132ac6b Mon Sep 17 00:00:00 2001 From: Oleg Nesterov Date: Thu, 17 Dec 2009 15:27:15 -0800 Subject: do_wait() optimization: do not place sub-threads on task_struct->children list Thanks to Roland who pointed out de_thread() issues. Currently we add sub-threads to ->real_parent->children list. This buys nothing but slows down do_wait(). With this patch ->children contains only main threads (group leaders). The only complication is that forget_original_parent() should iterate over sub-threads by hand, and de_thread() needs another list_replace() when it changes ->group_leader. Henceforth do_wait_thread() can never see task_detached() && !EXIT_DEAD tasks, we can remove this check (and we can unify do_wait_thread() and ptrace_do_wait()). This change can confuse the optimistic search in mm_update_next_owner(), but this is fixable and minor. Perhaps badness() and oom_kill_process() should be updated, but they should be fixed in any case. Signed-off-by: Oleg Nesterov Cc: Roland McGrath Cc: Ingo Molnar Cc: Ratan Nalumasu Cc: Vitaly Mayatskikh Cc: David Rientjes Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- fs/exec.c | 2 ++ 1 file changed, 2 insertions(+) (limited to 'fs') diff --git a/fs/exec.c b/fs/exec.c index 623a5cc3076..77db9a97a77 100644 --- a/fs/exec.c +++ b/fs/exec.c @@ -826,7 +826,9 @@ static int de_thread(struct task_struct *tsk) attach_pid(tsk, PIDTYPE_PID, task_pid(leader)); transfer_pid(leader, tsk, PIDTYPE_PGID); transfer_pid(leader, tsk, PIDTYPE_SID); + list_replace_rcu(&leader->tasks, &tsk->tasks); + list_replace_init(&leader->sibling, &tsk->sibling); tsk->group_leader = tsk; leader->group_leader = tsk; -- cgit v1.2.3