Hello, On Fri, Feb 27, 2015 at 11:42:10AM -0500, Austin S Hemmelgarn wrote: > Kernel memory consumption isn't the only valid reason to want to limit the > number of processes in a cgroup. Limiting the number of processes is very > useful to ensure that a program is working correctly (for example, the NTP > daemon should (usually) have an _exact_ number of children if it is > functioning correctly, and rpcbind shouldn't (AFAIK) ever have _any_ > children), to prevent PID number exhaustion, to head off DoS attacks against > forking network servers before they get to the point of causing kmem > exhaustion, and to limit the number of processes in a cgroup that uses lots > of kernel memory very infrequently. All the use cases you're listing are extremely niche and can be trivially achieved without introducing another cgroup controller. Not only that, they're actually pretty silly. Let's say NTP daemon is misbehaving (or its code changed w/o you knowing or there are corner cases which trigger extremely infrequently). What do you exactly achieve by rejecting its fork call? It's just adding another variation to the misbehavior. It was misbehaving before and would now be continuing to misbehave after a failed fork. In general, I'm pretty strongly against adding controllers for things which aren't fundamental resources in the system. What's next? Open files? Pipe buffer? Number of flocks? Number of session leaders or program groups? If you want to prevent a certain class of jobs from exhausting a given resource, protecting that resource is the obvious thing to do. Thanks. -- tejun -- To unsubscribe from this list: send the line "unsubscribe cgroups" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
