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authorChris Down <chris@chrisdown.name>2019-05-31 22:30:22 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2019-06-01 15:51:31 -0700
commit9852ae3fe5293264f01c49f2571ef7688f7823ce (patch)
tree6e9847c13762ce77ab3eb1e7a604be7b9cf6c09a
parentbc81426f5beef7da863d3365bc9d45e820448745 (diff)
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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. akpm: this is a behaviour change, so Cc:stable. THis is so that forthcoming distros which use cgroup v2 are more likely to pick up the revised behaviour. Link: http://lkml.kernel.org/r/20190208224419.GA24772@chrisdown.name Signed-off-by: Chris Down <chris@chrisdown.name> Acked-by: Johannes Weiner <hannes@cmpxchg.org> Reviewed-by: Shakeel Butt <shakeelb@google.com> Cc: Michal Hocko <mhocko@kernel.org> Cc: Tejun Heo <tj@kernel.org> Cc: Roman Gushchin <guro@fb.com> Cc: Dennis Zhou <dennis@kernel.org> Cc: Suren Baghdasaryan <surenb@google.com> Cc: <stable@vger.kernel.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
-rw-r--r--Documentation/admin-guide/cgroup-v2.rst9
-rw-r--r--include/linux/cgroup-defs.h5
-rw-r--r--include/linux/memcontrol.h10
-rw-r--r--kernel/cgroup/cgroup.c16
4 files changed, 36 insertions, 4 deletions
diff --git a/Documentation/admin-guide/cgroup-v2.rst b/Documentation/admin-guide/cgroup-v2.rst
index 88e746074252..cf88c1f98270 100644
--- a/Documentation/admin-guide/cgroup-v2.rst
+++ b/Documentation/admin-guide/cgroup-v2.rst
@@ -177,6 +177,15 @@ cgroup v2 currently supports the following mount options.
ignored on non-init namespace mounts. Please refer to the
Delegation section for details.
+ memory_localevents
+
+ Only populate memory.events with data for the current cgroup,
+ and not any subtrees. This is legacy behaviour, the default
+ behaviour without this option is to include subtree counts.
+ This option is system wide and can only be set on mount or
+ modified through remount from the init namespace. The mount
+ option is ignored on non-init namespace mounts.
+
Organizing Processes and Threads
--------------------------------
diff --git a/include/linux/cgroup-defs.h b/include/linux/cgroup-defs.h
index 77258d276f93..11e215d7937e 100644
--- a/include/linux/cgroup-defs.h
+++ b/include/linux/cgroup-defs.h
@@ -89,6 +89,11 @@ enum {
* Enable cpuset controller in v1 cgroup to use v2 behavior.
*/
CGRP_ROOT_CPUSET_V2_MODE = (1 << 4),
+
+ /*
+ * Enable legacy local memory.events.
+ */
+ CGRP_ROOT_MEMORY_LOCAL_EVENTS = (1 << 5),
};
/* cftype->flags */
diff --git a/include/linux/memcontrol.h b/include/linux/memcontrol.h
index 73fe0a700911..edf9e8f32d70 100644
--- a/include/linux/memcontrol.h
+++ b/include/linux/memcontrol.h
@@ -737,8 +737,14 @@ 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[event]);
- cgroup_file_notify(&memcg->events_file);
+ do {
+ atomic_long_inc(&memcg->memory_events[event]);
+ cgroup_file_notify(&memcg->events_file);
+
+ if (cgrp_dfl_root.flags & CGRP_ROOT_MEMORY_LOCAL_EVENTS)
+ break;
+ } while ((memcg = parent_mem_cgroup(memcg)) &&
+ !mem_cgroup_is_root(memcg));
}
static inline void memcg_memory_event_mm(struct mm_struct *mm,
diff --git a/kernel/cgroup/cgroup.c b/kernel/cgroup/cgroup.c
index 217cec4e22c6..426a0026225c 100644
--- a/kernel/cgroup/cgroup.c
+++ b/kernel/cgroup/cgroup.c
@@ -1810,11 +1810,13 @@ int cgroup_show_path(struct seq_file *sf, struct kernfs_node *kf_node,
enum cgroup2_param {
Opt_nsdelegate,
+ Opt_memory_localevents,
nr__cgroup2_params
};
static const struct fs_parameter_spec cgroup2_param_specs[] = {
- fsparam_flag ("nsdelegate", Opt_nsdelegate),
+ fsparam_flag("nsdelegate", Opt_nsdelegate),
+ fsparam_flag("memory_localevents", Opt_memory_localevents),
{}
};
@@ -1837,6 +1839,9 @@ static int cgroup2_parse_param(struct fs_context *fc, struct fs_parameter *param
case Opt_nsdelegate:
ctx->flags |= CGRP_ROOT_NS_DELEGATE;
return 0;
+ case Opt_memory_localevents:
+ ctx->flags |= CGRP_ROOT_MEMORY_LOCAL_EVENTS;
+ return 0;
}
return -EINVAL;
}
@@ -1848,6 +1853,11 @@ static void apply_cgroup_root_flags(unsigned int root_flags)
cgrp_dfl_root.flags |= CGRP_ROOT_NS_DELEGATE;
else
cgrp_dfl_root.flags &= ~CGRP_ROOT_NS_DELEGATE;
+
+ if (root_flags & CGRP_ROOT_MEMORY_LOCAL_EVENTS)
+ cgrp_dfl_root.flags |= CGRP_ROOT_MEMORY_LOCAL_EVENTS;
+ else
+ cgrp_dfl_root.flags &= ~CGRP_ROOT_MEMORY_LOCAL_EVENTS;
}
}
@@ -1855,6 +1865,8 @@ static int cgroup_show_options(struct seq_file *seq, struct kernfs_root *kf_root
{
if (cgrp_dfl_root.flags & CGRP_ROOT_NS_DELEGATE)
seq_puts(seq, ",nsdelegate");
+ if (cgrp_dfl_root.flags & CGRP_ROOT_MEMORY_LOCAL_EVENTS)
+ seq_puts(seq, ",memory_localevents");
return 0;
}
@@ -6325,7 +6337,7 @@ static struct kobj_attribute cgroup_delegate_attr = __ATTR_RO(delegate);
static ssize_t features_show(struct kobject *kobj, struct kobj_attribute *attr,
char *buf)
{
- return snprintf(buf, PAGE_SIZE, "nsdelegate\n");
+ return snprintf(buf, PAGE_SIZE, "nsdelegate\nmemory_localevents\n");
}
static struct kobj_attribute cgroup_features_attr = __ATTR_RO(features);