On Fri, 25 Mar 2011 11:38:19 +0900 Minchan Kim <minchan.kim@xxxxxxxxx> wrote: > On Fri, Mar 25, 2011 at 9:04 AM, KAMEZAWA Hiroyuki > <kamezawa.hiroyu@xxxxxxxxxxxxxx> wrote: > > On Thu, 24 Mar 2011 19:52:22 +0900 > > Minchan Kim <minchan.kim@xxxxxxxxx> wrote: > > To me, the fact "the system _can_ be broken by a normal user program" is the most > > terrible thing. With Andrey's case or make -j, a user doesn't need to be an admin. > > I believe it's worth to pay costs. > > (and I made this function configurable and can be turned off by sysfs.) > > > > And while testing Andrey's case, I used KVM finaly becasue cost of rebooting was small. > > My development server is on other building and I need to push server's button > > to reboot it when forkbomb happens ;) > > In some environement, cost of rebooting is not small even if it's a development system. > > > > Forkbomb is very rare case in normal situation but if it happens, the > cost like reboot would be big. So we need the such facility. I agree. > (But I don't know why others don't have a interest if it is important > task. Maybe they are so busy due to rc1) > Just a concern is cost. me, too. > The approach is we can enhance your approach to minimize the cost but > apparently it would have a limitation. > agreed. "tracking" always costs. > Other approach is we can provide new rescue facility. > What I have thought is new sysrq about killing fork-bomb. > Mine works fine with Sysrq+f. But, I need to go to other building for pushing Sysrq..... > If we execute the new sysrq, the kernel freezes all tasks so forkbomb > can't execute any more and kernel ready to receive the command to show > the system state. Admin can investigate which is fork-bomb and then he > kill the tasks. At last, admin restarts all processes with new sysrq > and processes which received SIGKILL start to die. > > This approach offloads kernel's heuristic forkbomb detection to admin > and avoid runtime cost in normal situation. > I don't have any code to implement above the concept so it might be ridiculous. > > What do you think about it? > For usual user, forkbmob killer works better, rather than special console for fatal system. I can think of 2 similar works. One is Windows's TaskManager. You can kill tasks with it (and I guess TaskManager is always on memory...) Another one is "guarantee" or "preserve XXXX for special apps." which clustering guys wants for quick server failover. If trouble happens, - freeze all apps other than HA apps. - open the gate for hidden preserved resources (of memory / disks) - do safe failover to other server. - do necessary jobs and reboot. So, you need to preserve some resources for recover...IOW, have to pay costs. BTW, Sysrq/TaskManager/Failover doesn't help me, using development system via network. 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 internet charges in Canada: sign http://stopthemeter.ca/ Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>