On Sun, Dec 20, 2020 at 7:56 PM Shakeel Butt <shakeelb@xxxxxxxxxx> wrote: > > On Sun, Dec 20, 2020 at 3:31 AM Amir Goldstein <amir73il@xxxxxxxxx> wrote: > > > > On Sun, Dec 20, 2020 at 6:24 AM Shakeel Butt <shakeelb@xxxxxxxxxx> wrote: > > > > > > On Sat, Dec 19, 2020 at 8:25 AM Amir Goldstein <amir73il@xxxxxxxxx> wrote: > > > > > > > > On Sat, Dec 19, 2020 at 4:31 PM Shakeel Butt <shakeelb@xxxxxxxxxx> wrote: > > > > > > > > > > On Sat, Dec 19, 2020 at 1:48 AM Amir Goldstein <amir73il@xxxxxxxxx> wrote: > > > > > > > > > > > > On Sat, Dec 19, 2020 at 12:11 AM Shakeel Butt <shakeelb@xxxxxxxxxx> wrote: > > > > > > > > > > > > > > Currently the fs sysctl inotify/max_user_instances is used to limit the > > > > > > > number of inotify instances on the system. For systems running multiple > > > > > > > workloads, the per-user namespace sysctl max_inotify_instances can be > > > > > > > used to further partition inotify instances. However there is no easy > > > > > > > way to set a sensible system level max limit on inotify instances and > > > > > > > further partition it between the workloads. It is much easier to charge > > > > > > > the underlying resource (i.e. memory) behind the inotify instances to > > > > > > > the memcg of the workload and let their memory limits limit the number > > > > > > > of inotify instances they can create. > > > > > > > > > > > > Not that I have a problem with this patch, but what problem does it try to > > > > > > solve? > > > > > > > > > > I am aiming for the simplicity to not set another limit which can > > > > > indirectly be limited by memcg limits. I just want to set the memcg > > > > > limit on our production environment which runs multiple workloads on a > > > > > system and not think about setting a sensible value to > > > > > max_user_instances in production. I would prefer to set > > > > > max_user_instances to max int and let the memcg limits of the > > > > > workloads limit their inotify usage. > > > > > > > > > > > > > understood. > > > > and I guess the multiple workloads cannot run each in their own userns? > > > > because then you wouldn't need to change max_user_instances limit. > > > > > > > > > > No workloads can run in their own user namespace but please note that > > > max_user_instances is shared between all the user namespaces. > > > > /proc/sys/fs/inotify/max_user_instances is shared between all the user > > namespaces, but it only controls the init_user_ns limits. > > /proc/sys/user/max_inotify_instances is per user ns and it is the one that > > actually controls the inotify limits in non init_user_ns. > > > > That said, I see that it is always initialized to MAX_INT on non init user ns, > > which is exactly the setup that you are aiming at: > > > > $ unshare -U > > $ cat /proc/sys/user/max_inotify_instances > > 2147483647 > > $ cat /proc/sys/fs/inotify/max_user_instances > > 128 > > From what I understand, namespace-based limits are enforced > hierarchically. More specifically in the example above, the > application running in a user namespace with > /proc/sys/user/max_inotify_instances = 2147483647 and > /proc/sys/fs/inotify/max_user_instances = 128 will not be able to > create more than 128 inotify instances. I actually tested this with a > simple program which calls inotify_init() in a loop and it starts > failing before the 128th iteration. Right, it is. Thanks for the clarification. Thanks, Amir.
