From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail172.messagelabs.com (mail172.messagelabs.com [216.82.254.3]) by kanga.kvack.org (Postfix) with ESMTP id B2DB68D0040 for ; Fri, 25 Mar 2011 00:05:54 -0400 (EDT) Received: by iyf13 with SMTP id 13so932160iyf.14 for ; Thu, 24 Mar 2011 21:05:50 -0700 (PDT) MIME-Version: 1.0 In-Reply-To: <20110325115453.82a9736d.kamezawa.hiroyu@jp.fujitsu.com> References: <20110324182240.5fe56de2.kamezawa.hiroyu@jp.fujitsu.com> <20110324105222.GA2625@barrios-desktop> <20110325090411.56c5e5b2.kamezawa.hiroyu@jp.fujitsu.com> <20110325115453.82a9736d.kamezawa.hiroyu@jp.fujitsu.com> Date: Fri, 25 Mar 2011 13:05:50 +0900 Message-ID: Subject: Re: [PATCH 0/4] forkbomb killer From: Minchan Kim Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: quoted-printable Sender: owner-linux-mm@kvack.org List-ID: To: KAMEZAWA Hiroyuki Cc: "linux-mm@kvack.org" , "linux-kernel@vger.kernel.org" , "rientjes@google.com" , Andrey Vagin , KOSAKI Motohiro , Hugh Dickins , Johannes Weiner , Rik van Riel On Fri, Mar 25, 2011 at 11:54 AM, KAMEZAWA Hiroyuki wrote: > On Fri, 25 Mar 2011 11:38:19 +0900 > Minchan Kim wrote: > >> On Fri, Mar 25, 2011 at 9:04 AM, KAMEZAWA Hiroyuki >> wrote: >> > On Thu, 24 Mar 2011 19:52:22 +0900 >> > Minchan Kim 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 reb= ooting 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 de= velopment 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 ridi= culous. >> >> 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 kil= l tasks > with it (and I guess TaskManager is always on memory...) Another one is > "guarantee" or "preserve XXXX for special apps." which clustering guys wa= nts for > quick server failover. > > If trouble happens, > =C2=A0- freeze all apps other than HA apps. > =C2=A0- open the gate for hidden preserved resources (of memory / disks) > =C2=A0- do safe failover to other server. > =C2=A0- do necessary jobs and reboot. > > So, you need to preserve some resources for recover...IOW, have to pay co= sts. > > BTW, Sysrq/TaskManager/Failover doesn't help me, using development system= via network. Okay. Each approach has a pros and cons and at least, now anyone doesn't provide any method and comments but I agree it is needed(ex, careless and lazy admin could need it strongly). Let us wait a little bit more. Maybe google guys or redhat/suse guys would have a opinion. Regardless of them, I will review series when I have rest time. Thanks, Kame. --=20 Kind regards, Minchan Kim -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. 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: email@kvack.org