On Thu, 24 Mar 2011 19:52:22 +0900 Minchan Kim <minchan.kim@xxxxxxxxx> wrote: > Hi Kame, > Hi. > On Thu, Mar 24, 2011 at 06:22:40PM +0900, KAMEZAWA Hiroyuki wrote: > > > > I tested with several forkbomb cases and this patch seems work fine. > > > > Maybe some more 'heuristics' can be added....but I think this simple > > one works enough. Any comments are welcome. > > Sorry for the late review. Recently I dont' have enough time to review patches. > Even I didn't start to review this series but I want to review this series. > It's one of my interest features. :) > > But before digging in code, I would like to make a consensus to others to > need this feature. Let's Cc others. > > What I think is that about "cost(frequent case) VS effectiveness(very rare case)" > as you expected. :) > > 1. At least, I don't meet any fork-bomb case for a few years. My primary linux usage > is just desktop and developement enviroment, NOT server. Only thing I have seen is > just ltp or intentional fork-bomb test like hackbench. AFAIR, ltp case was fixed > a few years ago. Although it happens suddenly, reboot in desktop isn't critical > as much as server's one. > Personally, I've met forkbombs several times by typing "make -j" .....by mistake. I met a forkbomb on production system by buggy script, once. That happens because 1. $PATH includes "." 2. a programmer write a scirpt "date" and call "date" in the script. Maybe this is a one of typical case of forkbomb. I needed to dig crashdump to find fragile of page-caches and see what happens...But, I guess, if appearent forkbomb happens, the issue will not be sent to my team because we're 2nd line support team and 1st line should block it ;). So, I'm not sure how many forkbombs happens in server world in a year. But I guess forkbomb still happens in many development systems because there is no guard against it. > 2. I don't know server enviroment but I think applications executing on server > are selected by admin carefully. So virus program like fork-bomb is unlikely in there. > (Maybe I am wrong. You know than me). > If some normal program becomes fork-bomb unexpectedly, it's critical. > Admin should select application with much testing very carefully. But I don't know > the reality. :( > Yes, admin selects applications carefully. There is no 100% protection by human's hand. > Of course, although he did such efforts, he could meet OOM hang situation. > In the case, he can't avoid rebooting. Sad. But for helping him, should we pay cost > in normal situation?(Again said, I didn't start looking at your code so > I can't expect the cost but at least it's more than as-is). > It could help developing many virus program and to make careless admins. > > It's just my private opinion. > I don't have enough experience so I hope listen other's opinions > about generic fork-bomb killer, not memcg. > > I don't intend to ignore your effort but justify your and my effort rightly. > 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. 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>