From: Shakeel Butt <shakeelb@xxxxxxxxxx> Subject: mm, memcg: introduce memory.events.local 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. Link: http://lkml.kernel.org/r/20190527174643.209172-1-shakeelb@xxxxxxxxxx Signed-off-by: Shakeel Butt <shakeelb@xxxxxxxxxx> Reviewed-by: Roman Gushchin <guro@xxxxxx> Acked-by: Johannes Weiner <hannes@xxxxxxxxxxx> Acked-by: Michal Hocko <mhocko@xxxxxxxx> Cc: Vladimir Davydov <vdavydov.dev@xxxxxxxxx> Cc: Chris Down <chris@xxxxxxxxxxxxxx> Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> --- Documentation/admin-guide/cgroup-v2.rst | 10 ++++++ include/linux/memcontrol.h | 7 +++- mm/memcontrol.c | 34 +++++++++++++++------- 3 files changed, 40 insertions(+), 11 deletions(-) --- a/Documentation/admin-guide/cgroup-v2.rst~mm-memcg-introduce-memoryeventslocal +++ a/Documentation/admin-guide/cgroup-v2.rst @@ -1146,6 +1146,11 @@ 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 @@ -1185,6 +1190,11 @@ 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. --- a/include/linux/memcontrol.h~mm-memcg-introduce-memoryeventslocal +++ a/include/linux/memcontrol.h @@ -232,8 +232,9 @@ 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; @@ -280,6 +281,7 @@ struct mem_cgroup { /* memory.events */ atomic_long_t memory_events[MEMCG_NR_MEMORY_EVENTS]; + atomic_long_t memory_events_local[MEMCG_NR_MEMORY_EVENTS]; unsigned long socket_pressure; @@ -746,6 +748,9 @@ static inline void count_memcg_event_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); --- a/mm/memcontrol.c~mm-memcg-introduce-memoryeventslocal +++ a/mm/memcontrol.c @@ -5617,21 +5617,29 @@ static ssize_t memory_max_write(struct k 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; } @@ -5794,6 +5802,12 @@ static struct cftype memory_files[] = { .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, .seq_show = memory_stat_show, _
