Messages in this thread | | | From | Al Boldi <> | Subject | Re: Resource limits | Date | Tue, 27 Sep 2005 16:42:07 +0300 |
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Neil Horman wrote: > On Tue, Sep 27, 2005 at 08:08:21AM +0300, Al Boldi wrote: > > Neil Horman wrote: > > > On Mon, Sep 26, 2005 at 11:26:10PM +0300, Al Boldi wrote: > > > > Neil Horman wrote: > > > > > On Mon, Sep 26, 2005 at 08:32:14PM +0300, Al Boldi wrote: > > > > > > Neil Horman wrote: > > > > > > > On Mon, Sep 26, 2005 at 05:18:17PM +0300, Al Boldi wrote: > > > > > > > > Rik van Riel wrote: > > > > > > > > > On Sun, 25 Sep 2005, Al Boldi wrote: > > > > > > > > > > Too many process forks and your system may crash. > > > > > > > > > > This can be capped with threads-max, but may lead you > > > > > > > > > > into a lock-out. > > > > > > > > > > > > > > > > > > > > What is needed is a soft, hard, and a special emergency > > > > > > > > > > limit that would allow you to use the resource for a > > > > > > > > > > limited time to circumvent a lock-out. > > > > > > > > > > > > > > > > > > How would you reclaim the resource after that limited time > > > > > > > > > is over ? Kill processes? > > > > > > > > > > > > > > > > That's one way, but really, the issue needs some deep > > > > > > > > thought. Leaving Linux exposed to a lock-out is rather > > > > > > > > frightening. > > > > > > > > > > > > > > What exactly is it that you're worried about here? > > > > > > > > > > > > Think about a DoS attack. > > > > > > > > > > Be more specific. Are you talking about a fork bomb, a ICMP > > > > > flood, what? > > > > Consider this dilemma: > > Runaway proc/s hit the limit. > > Try to kill some and you are denied due to the resource limit. > > Use some previously running app like top, hope it hasn't been killed by > > some OOM situation, try killing some procs and another one takes it's > > place because of the runaway situation. > > Raise the limit, and it gets filled by the runaways. > > You are pretty much stuck. > > Not really, this is the sort of thing ulimit is meant for. To keep > processes from any one user from running away. It lets you limit the > damage it can do, until such time as you can control it and fix the > runaway application.
threads-max = 1024 ulimit = 100 forks 11 runaway procs hitting the threads-max limit
This example is extreme, but it's possible, and there should be a safe and easy way out.
What do you think?
Thanks! -- Al
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