On Wed, 22 Dec 2010 01:21:01 -0800 (PST) David Rientjes <rientjes@xxxxxxxxxx> wrote: > On Wed, 22 Dec 2010, KAMEZAWA Hiroyuki wrote: > > > For example. oom_check_deadlockd can work as > > > > 1. disable oom by memory.oom_disable=1 > > 2. check memory.oom_notify and wait it by poll() > > 3. At oom, it wakes up. > > 4. wait for 60 secs. > > 5. If the cgroup is still in OOM, set oom_disalble=0 > > > > This daemon will not use much memory and can run in /roog memory cgroup. > > > > Yes, this is almost the same as the "simple and perfect implementation" > that I eluded to in my response to Andrew (and I think KOSAKI-san > suggested something similiar), although it doesn't quite work because all > threads in the cgroup are sitting on the waitqueue and don't get woken up > to see oom_control == 0 unless memory is freed, a task is moved, or the > limit is resized so this daemon will need to trigger that as step #6. > > That certainly works if it is indeed perfect and guaranteed to always be > running. In the interest of a robust resource isolation model, I don't > think we can ever make that conclusion, though, so this discussion is > really only about how fault tolerant the kernel is because the end result > is if this daemon fails, the kernel livelocks. > > I'd personally prefer not to allow a buggy or imperfect userspace to allow > the kernel to livelock; we control the kernel so I think it would be best > to ensure that it cannot livelock no matter what userspace happens to do > despite its best effort. If you or Andrew come to the conclusion that > it's overkill and at the end of the day we have to trust userspace, I > really can't argue that philosophy though :) > It's not livelock. A user can create a new thread in a cgroup not under OOM. IMHO, oom-kill itself is totally of-no-use and panic_at_oom or the system stop is always good. We can do cluster keep alive. If I was you, I'll add a "pool of memory for emergency cgroup" and run watchdog tasks in it. Thanks, -Kame -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxxx For more info on Linux MM, see: http://www.linux-mm.org/ . Fight unfair telecom policy in Canada: sign http://dissolvethecrtc.ca/ Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>