On Mon 27-05-19 10:46:43, Shakeel Butt wrote: > The memory controller in cgroup v2 exposes memory.events file for each > memcg which shows the number of times events like low, high, max, oom > and oom_kill have happened for the whole tree rooted at that memcg. > Users can also poll or register notification to monitor the changes in > that file. Any event at any level of the tree rooted at memcg will > notify all the listeners along the path till root_mem_cgroup. There are > existing users which depend on this behavior. > > However there are users which are only interested in the events > happening at a specific level of the memcg tree and not in the events in > the underlying tree rooted at that memcg. One such use-case is a > centralized resource monitor which can dynamically adjust the limits of > the jobs running on a system. The jobs can create their sub-hierarchy > for their own sub-tasks. The centralized monitor is only interested in > the events at the top level memcgs of the jobs as it can then act and > adjust the limits of the jobs. Using the current memory.events for such > centralized monitor is very inconvenient. The monitor will keep > receiving events which it is not interested and to find if the received > event is interesting, it has to read memory.event files of the next > level and compare it with the top level one. So, let's introduce > memory.events.local to the memcg which shows and notify for the events > at the memcg level. > > Now, does memory.stat and memory.pressure need their local versions. > IMHO no due to the no internal process contraint of the cgroup v2. The > memory.stat file of the top level memcg of a job shows the stats and > vmevents of the whole tree. The local stats or vmevents of the top level > memcg will only change if there is a process running in that memcg but > v2 does not allow that. Similarly for memory.pressure there will not be > any process in the internal nodes and thus no chance of local pressure. > > Signed-off-by: Shakeel Butt <[email protected]> > Reviewed-by: Roman Gushchin <[email protected]> > Acked-by: Johannes Weiner <[email protected]>
As there seems to be a larger agreement that the default behavior of memory.events is going to be hierarchical then this addition makes a lot of sense. Acked-by: Michal Hocko <[email protected]> > --- > Changelog since v2: > - Added documentation. > > Changelog since v1: > - refactor memory_events_show to share between events and events.local > > Documentation/admin-guide/cgroup-v2.rst | 10 ++++++++ > include/linux/memcontrol.h | 7 ++++- > mm/memcontrol.c | 34 +++++++++++++++++-------- > 3 files changed, 40 insertions(+), 11 deletions(-) > > diff --git a/Documentation/admin-guide/cgroup-v2.rst > b/Documentation/admin-guide/cgroup-v2.rst > index 19c4e78666ff..0e961fc90cd9 100644 > --- a/Documentation/admin-guide/cgroup-v2.rst > +++ b/Documentation/admin-guide/cgroup-v2.rst > @@ -1119,6 +1119,11 @@ PAGE_SIZE multiple when read back. > otherwise, a value change in this file generates a file > modified event. > > + Note that all fields in this file are hierarchical and the > + file modified event can be generated due to an event down the > + hierarchy. For for the local events at the cgroup level see > + memory.events.local. > + > low > The number of times the cgroup is reclaimed due to > high memory pressure even though its usage is under > @@ -1158,6 +1163,11 @@ PAGE_SIZE multiple when read back. > The number of processes belonging to this cgroup > killed by any kind of OOM killer. > > + memory.events.local > + Similar to memory.events but the fields in the file are local > + to the cgroup i.e. not hierarchical. The file modified event > + generated on this file reflects only the local events. > + > memory.stat > A read-only flat-keyed file which exists on non-root cgroups. > > diff --git a/include/linux/memcontrol.h b/include/linux/memcontrol.h > index 36bdfe8e5965..de77405eec46 100644 > --- a/include/linux/memcontrol.h > +++ b/include/linux/memcontrol.h > @@ -239,8 +239,9 @@ struct mem_cgroup { > /* OOM-Killer disable */ > int oom_kill_disable; > > - /* memory.events */ > + /* memory.events and memory.events.local */ > struct cgroup_file events_file; > + struct cgroup_file events_local_file; > > /* handle for "memory.swap.events" */ > struct cgroup_file swap_events_file; > @@ -286,6 +287,7 @@ struct mem_cgroup { > atomic_long_t vmevents_local[NR_VM_EVENT_ITEMS]; > > atomic_long_t memory_events[MEMCG_NR_MEMORY_EVENTS]; > + atomic_long_t memory_events_local[MEMCG_NR_MEMORY_EVENTS]; > > unsigned long socket_pressure; > > @@ -761,6 +763,9 @@ static inline void count_memcg_event_mm(struct mm_struct > *mm, > static inline void memcg_memory_event(struct mem_cgroup *memcg, > enum memcg_memory_event event) > { > + atomic_long_inc(&memcg->memory_events_local[event]); > + cgroup_file_notify(&memcg->events_local_file); > + > do { > atomic_long_inc(&memcg->memory_events[event]); > cgroup_file_notify(&memcg->events_file); > diff --git a/mm/memcontrol.c b/mm/memcontrol.c > index 2713b45ec3f0..a57dfcc4c4a4 100644 > --- a/mm/memcontrol.c > +++ b/mm/memcontrol.c > @@ -5630,21 +5630,29 @@ static ssize_t memory_max_write(struct > kernfs_open_file *of, > return nbytes; > } > > +static void __memory_events_show(struct seq_file *m, atomic_long_t *events) > +{ > + seq_printf(m, "low %lu\n", atomic_long_read(&events[MEMCG_LOW])); > + seq_printf(m, "high %lu\n", atomic_long_read(&events[MEMCG_HIGH])); > + seq_printf(m, "max %lu\n", atomic_long_read(&events[MEMCG_MAX])); > + seq_printf(m, "oom %lu\n", atomic_long_read(&events[MEMCG_OOM])); > + seq_printf(m, "oom_kill %lu\n", > + atomic_long_read(&events[MEMCG_OOM_KILL])); > +} > + > static int memory_events_show(struct seq_file *m, void *v) > { > struct mem_cgroup *memcg = mem_cgroup_from_seq(m); > > - seq_printf(m, "low %lu\n", > - atomic_long_read(&memcg->memory_events[MEMCG_LOW])); > - seq_printf(m, "high %lu\n", > - atomic_long_read(&memcg->memory_events[MEMCG_HIGH])); > - seq_printf(m, "max %lu\n", > - atomic_long_read(&memcg->memory_events[MEMCG_MAX])); > - seq_printf(m, "oom %lu\n", > - atomic_long_read(&memcg->memory_events[MEMCG_OOM])); > - seq_printf(m, "oom_kill %lu\n", > - atomic_long_read(&memcg->memory_events[MEMCG_OOM_KILL])); > + __memory_events_show(m, memcg->memory_events); > + return 0; > +} > + > +static int memory_events_local_show(struct seq_file *m, void *v) > +{ > + struct mem_cgroup *memcg = mem_cgroup_from_seq(m); > > + __memory_events_show(m, memcg->memory_events_local); > return 0; > } > > @@ -5806,6 +5814,12 @@ static struct cftype memory_files[] = { > .file_offset = offsetof(struct mem_cgroup, events_file), > .seq_show = memory_events_show, > }, > + { > + .name = "events.local", > + .flags = CFTYPE_NOT_ON_ROOT, > + .file_offset = offsetof(struct mem_cgroup, events_local_file), > + .seq_show = memory_events_local_show, > + }, > { > .name = "stat", > .flags = CFTYPE_NOT_ON_ROOT, > -- > 2.22.0.rc1.257.g3120a18244-goog -- Michal Hocko SUSE Labs
