On Thu 16-05-19 13:56:55, Johannes Weiner wrote: > On Wed, Feb 13, 2019 at 01:47:29PM +0100, Michal Hocko wrote: > > On Tue 12-02-19 14:45:42, Andrew Morton wrote: > > [...] > > > From: Chris Down <chris@xxxxxxxxxxxxxx> > > > Subject: mm, memcg: consider subtrees in memory.events > > > > > > memory.stat and other files already consider subtrees in their output, and > > > we should too in order to not present an inconsistent interface. > > > > > > The current situation is fairly confusing, because people interacting with > > > cgroups expect hierarchical behaviour in the vein of memory.stat, > > > cgroup.events, and other files. For example, this causes confusion when > > > debugging reclaim events under low, as currently these always read "0" at > > > non-leaf memcg nodes, which frequently causes people to misdiagnose breach > > > behaviour. The same confusion applies to other counters in this file when > > > debugging issues. > > > > > > Aggregation is done at write time instead of at read-time since these > > > counters aren't hot (unlike memory.stat which is per-page, so it does it > > > at read time), and it makes sense to bundle this with the file > > > notifications. > > > > > > After this patch, events are propagated up the hierarchy: > > > > > > [root@ktst ~]# cat /sys/fs/cgroup/system.slice/memory.events > > > low 0 > > > high 0 > > > max 0 > > > oom 0 > > > oom_kill 0 > > > [root@ktst ~]# systemd-run -p MemoryMax=1 true > > > Running as unit: run-r251162a189fb4562b9dabfdc9b0422f5.service > > > [root@ktst ~]# cat /sys/fs/cgroup/system.slice/memory.events > > > low 0 > > > high 0 > > > max 7 > > > oom 1 > > > oom_kill 1 > > > > > > As this is a change in behaviour, this can be reverted to the old > > > behaviour by mounting with the `memory_localevents' flag set. However, we > > > use the new behaviour by default as there's a lack of evidence that there > > > are any current users of memory.events that would find this change > > > undesirable. > > > > > > Link: http://lkml.kernel.org/r/20190208224419.GA24772@xxxxxxxxxxxxxx > > > Signed-off-by: Chris Down <chris@xxxxxxxxxxxxxx> > > > Acked-by: Johannes Weiner <hannes@xxxxxxxxxxx> > > > Cc: Michal Hocko <mhocko@xxxxxxxxxx> > > > Cc: Tejun Heo <tj@xxxxxxxxxx> > > > Cc: Roman Gushchin <guro@xxxxxx> > > > Cc: Dennis Zhou <dennis@xxxxxxxxxx> > > > Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> > > > > FTR: As I've already said here [1] I can live with this change as long > > as there is a larger consensus among cgroup v2 users. So let's give this > > some more time before merging to see whether there is such a consensus. > > > > [1] http://lkml.kernel.org/r/20190201102515.GK11599@xxxxxxxxxxxxxx > > It's been three months without any objections. It's been three months without any _feedback_ from anybody. It might very well be true that people just do not read these emails or do not care one way or another. > Can we merge this for > v5.2 please? We still have users complaining about this inconsistent > behavior (the last one was yesterday) and we'd rather not carry any > out of tree patches. Could you point me to those complains or is this something internal? -- Michal Hocko SUSE Labs
