Hello Oleg, On Sun, 2010-09-26 at 20:11 +0200, Oleg Nesterov wrote: > > I think one place was "khelper" (kmod.c). It is created with > > kernel_thread() and it exits without having accounted the times with > > sys_wait() to the parent's ctimes > > No. Well yes, it is not accounted, but this is not because it is > kthread. > > To simplify the discussion, lets talk about utime/cutime only, > and lets forget about the multithreading. > > It is very simple, currently linux accounts the exiting task's > utime and adds its to ->cutime _only_ if parent does do_wait(). > If parent ignores SIGCHLD, the child reaps itself and it is not > accounted. > > I do not know why it was done this way, but I'm afraid we can't > change this historical behaviour. Ok thanks, I didn't know this. So time can disappear, if the parent ignores SIGCHLD. I am a bit disappointed, because I thought by looking at all tasks of a system it should be possible to evaluate all consumed CPU time from now to the time where the system has been booted. That would have been a nice thing. > > Ok, the problem is that I did not consider exiting threads that are no > > thread group leaders. When they exit the ctime of the parent is not > > updated. Instead the time is accumulated in the signal struct. > > I think I am a bit confused, but see above. With or without threads > the whole process can exit without accounting. Sorry that I couldn't explain my thoughts clear enough, believe me, I tried my best :-) Michael -- To unsubscribe from this list: send the line "unsubscribe linux-s390" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
