On Tue, 1 Jun 2010, David Rientjes wrote: > On Tue, 1 Jun 2010, KOSAKI Motohiro wrote: > > > > Add a forkbomb penalty for processes that fork an excessively large > > > number of children to penalize that group of tasks and not others. A > > > threshold is configurable from userspace to determine how many first- > > > generation execve children (those with their own address spaces) a task > > > may have before it is considered a forkbomb. This can be tuned by > > > altering the value in /proc/sys/vm/oom_forkbomb_thres, which defaults to > > > 1000. > > > > > > When a task has more than 1000 first-generation children with different > > > address spaces than itself, a penalty of > > > > > > (average rss of children) * (# of 1st generation execve children) > > > ----------------------------------------------------------------- > > > oom_forkbomb_thres > > > > > > is assessed. So, for example, using the default oom_forkbomb_thres of > > > 1000, the penalty is twice the average rss of all its execve children if > > > there are 2000 such tasks. A task is considered to count toward the > > > threshold if its total runtime is less than one second; for 1000 of such > > > tasks to exist, the parent process must be forking at an extremely high > > > rate either erroneously or maliciously. > > > > > > Even though a particular task may be designated a forkbomb and selected as > > > the victim, the oom killer will still kill the 1st generation execve child > > > with the highest badness() score in its place. The avoids killing > > > important servers or system daemons. When a web server forks a very large > > > number of threads for client connections, for example, it is much better > > > to kill one of those threads than to kill the server and make it > > > unresponsive. > > > > > > [oleg@xxxxxxxxxx: optimize task_lock when iterating children] > > > Signed-off-by: David Rientjes <rientjes@xxxxxxxxxx> > > > > nack > > > > Why? > Still waiting for an answer to this, KOSAKI. -- 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/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>