On Tue, Jul 25, 2023 at 7:07 AM Michal Koutný <mkoutny@xxxxxxxx> wrote: > > Hello. > > On Mon, Jul 10, 2023 at 02:21:10PM -0700, Ivan Babrou <ivan@xxxxxxxxxxxxxx> wrote: > > I want to monitor cgroup changes, so that I can have an up to date map > > of inode -> cgroup path, so that I can resolve the value returned from > > bpf_get_current_cgroup_id() into something that a human can easily > > grasp (think system.slice/nginx.service). > > Have you considered cgroup_path_from_kernfs_id()? * It's not available from bpf from what I see (should I send a patch?) * It turns short numeric keys into large string keys (you mention this below) * It's a lot more work upfront for every event under a spinlock > > Currently I do a full sweep to build a map, which doesn't work if a > > cgroup is short lived, as it just disappears before I can resolve it. > > Unfortunately, systemd recycles cgroups on restart, changing inode > > number, so this is a very real issue. > > So, a historical map of cgroup id -> path is also useful for you, right? > (IOW, cgroup_path_from_kernfs_id() is possible but it'd inflate log > buffer size if full paths were stored instead of ids.) For the most part the historical map would not be necessary if we had cgroup paths (except for the points I mentioned above). > (I think a similar map would be beneficial for SCM_CGROUP [1] idea too.) Yes, it seems like it. > > There's also this old wiki page from systemd: > > > > * https://freedesktop.org/wiki/Software/systemd/Optimizations > > The page also states: > > > Last edited Sat 18 May 2013 08:20:38 AM UTC > > Emptiness notifications via release_agent are so 2016 :-), unified > hiearchy has more convenient API [2], this is FTR. Sure, but these aren't arguments against having fanotify for cgroup filesystem.
