On Mon, Jun 14, 2021 at 04:43:28PM -0400, Tejun Heo wrote: > Hello, > > On Mon, Jun 14, 2021 at 11:23:02AM -0400, Waiman Long wrote: > > The current container management system is able to create the illusion > > that applications running within a container have limited resources and > > devices available for their use. However, one thing that is hard to hide > > is the number of CPUs available in the system. In fact, the container > > developers are asking for the kernel to provide such capability. > > > > There are two places where cpu information are available for the > > applications to see - /proc/cpuinfo and /sys/devices/system/cpu sysfs > > directory. > > > > This patchset introduces a new sysctl parameter cpuset_bound_cpuinfo > > which, when set, will limit the amount of information disclosed by > > /proc/cpuinfo and /sys/devices/system/cpu. > > The goal of cgroup has never been masquerading system information so that > applications can pretend that they own the whole system and the proposed > solution requires application changes anyway. The information being provided > is useful but please do so within the usual cgroup interface - e.g. > cpuset.stat. The applications (or libraries) that want to determine its > confined CPU availability can locate the file through /proc/self/cgroup. Fyi, there's another concurrent push going on to provide a new file /proc/self/meminfo that is a subset of /proc/meminfo (cf. [1]) and virtualizes based on cgroups as well. But there it's a new file not virtualizing exisiting files and directories so there things seem to be out of sync between these groups at the same company. In any case I would like to point out that this has a complete solution in userspace. We have had this problem of providing virtualized information to containers since they started existing. So we created LXCFS in 2014 (cf. [2]) a tiny fuse fileystem to provide a virtualized view based on cgroups and other information for containers. The two patchsets seems like they're on the way trying to move 1:1 what we're already doing in userspace into the kernel. LXCFS is quite well known and widely used so it's suprising to not see it mentioned at all. And the container people will want more then just the cpu and meminfo stuff sooner or later. Just look at what we currently virtualize: /proc/cpuinfo /proc/diskstats /proc/meminfo /proc/stat /proc/swaps /proc/uptime /proc/slabinfo /sys/devices/system/cpu ## So for example /proc/cpuinfo #### Host brauner@wittgenstein|~ > grep ^processor /proc/cpuinfo processor : 0 processor : 1 processor : 2 processor : 3 processor : 4 processor : 5 processor : 6 processor : 7 #### Container brauner@wittgenstein|~ > lxc exec f1 -- grep ^processor /proc/cpuinfo processor : 0 processor : 1 ## and for /sys/devices/system/cpu #### Host brauner@wittgenstein|~ > ls -al /sys/devices/system/cpu/ | grep cpu[[:digit:]] drwxr-xr-x 10 root root 0 Jun 14 21:22 cpu0 drwxr-xr-x 10 root root 0 Jun 14 21:22 cpu1 drwxr-xr-x 10 root root 0 Jun 14 21:22 cpu2 drwxr-xr-x 10 root root 0 Jun 14 21:22 cpu3 drwxr-xr-x 10 root root 0 Jun 14 21:22 cpu4 drwxr-xr-x 10 root root 0 Jun 14 21:22 cpu5 drwxr-xr-x 10 root root 0 Jun 14 21:22 cpu6 drwxr-xr-x 10 root root 0 Jun 14 21:22 cpu7 #### Container brauner@wittgenstein|~ > lxc exec f1 -- ls -al /sys/devices/system/cpu/ | grep cpu[[:digit:]] drwxr-xr-x 2 nobody nogroup 0 Jun 15 09:07 cpu3 drwxr-xr-x 2 nobody nogroup 0 Jun 15 09:07 cpu4 We have a wide variety of users from various distros. [1]: https://lore.kernel.org/containers/f62b652c-3f6f-31ba-be0f-5f97b304599f@xxxxxxxxx [2]: https://github.com/lxc/lxcfs
