On Thu, Dec 12, 2013 at 04:35:09PM -0500, Dwight Engen wrote: > Hello, > > I've seen that some sort of fork/task limiter has been proposed and > discussed several times before. Despite the existance of kmem in memcg, a > fork limiter is still often asked for by container users. Perhaps this is > due to current granularity in kmem (ie. stack/struct task not split out from > other slab allocations) but I believe it is just more natural for users to > express a limit in terms of tasks. > > So what I've done is updated Frederic Weisbecker's task counter patchset and > tried to address the concerns that I saw people had raised. This involved > the following changes: > > - merged into cpuacct controller, as it seems there is a desire not to add > new controllers, this controller is already heirarchical, and I feel > limiting number of tasks/forks fits best here > - included a fork_limit similar to the one Max Kellermann posted > (https://lkml.org/lkml/2011/2/17/116) which is a use case not addressable > with memcg > - ala memcg kmem, for performance reasons don't account unless limit is set > - ala memcg, allow usage to roll up to root (prevents warnings on > uncharge), but still don't allow setting limits in root > - changed the interface at fork()/exit(), adding > can_fork()/cancel_can_fork() modeled on can_attach(). cgroup_fork() > can now return failure to fork(). > - ran Frederics selftests, and added a couple more > > I also wrote a small fork micro benchmark to see how this change affected > performance. I did 20 runs of 100000 fork/exit/waitpid, and took the > average. Times are in seconds, base is without the change, cpuacct1 is with > the change but no accounting be done (ie. no limit set), and cpuacct2 is > with the test being in a cgroup 1 level deep. > > base cpuacct1 cpuaac2 > 5.59 5.59 5.64 > > So I believe this change has minimal performance impact, especially when no > limit is set. Sorry for the late answer on this. I'm adding cgroup mailing list and a few cgroups/kmem people in Cc. This patchset was eventually abandoned because kmem became the prefered way to limit the number of tasks that can be forked. Have you tried it? Thanks. -- 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
