• Oleg Nesterov's avatar
    do_wait() optimization: do not place sub-threads on task_struct->children list · 9cd80bbb
    Oleg Nesterov authored
    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: default avatarOleg Nesterov <oleg@redhat.com>
    Cc: Roland McGrath <roland@redhat.com>
    Cc: Ingo Molnar <mingo@elte.hu>
    Cc: Ratan Nalumasu <rnalumasu@gmail.com>
    Cc: Vitaly Mayatskikh <vmayatsk@redhat.com>
    Cc: David Rientjes <rientjes@google.com>
    Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
    Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
    9cd80bbb
exec.c 44.5 KB