[PATCH v4 1/3] misc_cgroup: introduce misc.events to count failures

[PATCH v4 1/3] misc_cgroup: introduce misc.events to count failures

[brookxu]

From: Chunguang Xu <brookxu@tencent.com>

Introduce misc.events to make it easier for us to understand
the pressure of resources. Currently only the 'max' event is
implemented, which indicates the times the resource is about
to exceeds the max limit.

Signed-off-by: Chunguang Xu <brookxu@tencent.com>
Reviewed-by: Vipin Sharma <vipinsh@google.com>
Reviewed-by: Michal Koutný <mkoutny@suse.com>
---
v3: remove misc.events.local
v2: remove cgroup v1 files.

 include/linux/misc_cgroup.h |  5 +++++
 kernel/cgroup/misc.c        | 24 ++++++++++++++++++++++++
 2 files changed, 29 insertions(+)

diff --git a/include/linux/misc_cgroup.h b/include/linux/misc_cgroup.h
index da2367e..091f2d2 100644
--- a/include/linux/misc_cgroup.h
+++ b/include/linux/misc_cgroup.h
@@ -36,6 +36,7 @@ enum misc_res_type {
 struct misc_res {
 	unsigned long max;
 	atomic_long_t usage;
+	atomic_long_t events;
 	bool failed;
 };
 
@@ -46,6 +47,10 @@ struct misc_res {
  */
 struct misc_cg {
 	struct cgroup_subsys_state css;
+
+	/* misc.events */
+	struct cgroup_file events_file;
+
 	struct misc_res res[MISC_CG_RES_TYPES];
 };
 
diff --git a/kernel/cgroup/misc.c b/kernel/cgroup/misc.c
index ec02d96..4b2b492 100644
--- a/kernel/cgroup/misc.c
+++ b/kernel/cgroup/misc.c
@@ -171,6 +171,11 @@ int misc_cg_try_charge(enum misc_res_type type, struct misc_cg *cg,
 	return 0;
 
 err_charge:
+	for (j = i; j; j = parent_misc(j)) {
+		atomic_long_inc(&j->res[type].events);
+		cgroup_file_notify(&j->events_file);
+	}
+
 	for (j = cg; j != i; j = parent_misc(j))
 		misc_cg_cancel_charge(type, j, amount);
 	misc_cg_cancel_charge(type, i, amount);
@@ -335,6 +340,19 @@ static int misc_cg_capacity_show(struct seq_file *sf, void *v)
 	return 0;
 }
 
+static int misc_events_show(struct seq_file *sf, void *v)
+{
+	struct misc_cg *cg = css_misc(seq_css(sf));
+	unsigned long events, i;
+
+	for (i = 0; i < MISC_CG_RES_TYPES; i++) {
+		events = atomic_long_read(&cg->res[i].events);
+		if (READ_ONCE(misc_res_capacity[i]) || events)
+			seq_printf(sf, "%s.max %lu\n", misc_res_name[i], events);
+	}
+	return 0;
+}
+
 /* Misc cgroup interface files */
 static struct cftype misc_cg_files[] = {
 	{
@@ -353,6 +371,12 @@ static int misc_cg_capacity_show(struct seq_file *sf, void *v)
 		.seq_show = misc_cg_capacity_show,
 		.flags = CFTYPE_ONLY_ON_ROOT,
 	},
+	{
+		.name = "events",
+		.flags = CFTYPE_NOT_ON_ROOT,
+		.file_offset = offsetof(struct misc_cg, events_file),
+		.seq_show = misc_events_show,
+	},
 	{}
 };
 
-- 
1.8.3.1

[PATCH v4 1/3] misc_cgroup: introduce misc.events to count failures

[brookxu]

From: Chunguang Xu <brookxu-1Nz4purKYjRBDgjK7y7TUQ@public.gmane.org>

Introduce misc.events to make it easier for us to understand
the pressure of resources. Currently only the 'max' event is
implemented, which indicates the times the resource is about
to exceeds the max limit.

Signed-off-by: Chunguang Xu <brookxu-1Nz4purKYjRBDgjK7y7TUQ@public.gmane.org>
Reviewed-by: Vipin Sharma <vipinsh-hpIqsD4AKlfQT0dZR+AlfA@public.gmane.org>
Reviewed-by: Michal Koutn√Ω <mkoutny-IBi9RG/b67k@public.gmane.org>
---
v3: remove misc.events.local
v2: remove cgroup v1 files.

 include/linux/misc_cgroup.h |  5 +++++
 kernel/cgroup/misc.c        | 24 ++++++++++++++++++++++++
 2 files changed, 29 insertions(+)

diff --git a/include/linux/misc_cgroup.h b/include/linux/misc_cgroup.h
index da2367e..091f2d2 100644
--- a/include/linux/misc_cgroup.h
+++ b/include/linux/misc_cgroup.h
@@ -36,6 +36,7 @@ enum misc_res_type {
 struct misc_res {
 	unsigned long max;
 	atomic_long_t usage;
+	atomic_long_t events;
 	bool failed;
 };
 
@@ -46,6 +47,10 @@ struct misc_res {
  */
 struct misc_cg {
 	struct cgroup_subsys_state css;
+
+	/* misc.events */
+	struct cgroup_file events_file;
+
 	struct misc_res res[MISC_CG_RES_TYPES];
 };
 
diff --git a/kernel/cgroup/misc.c b/kernel/cgroup/misc.c
index ec02d96..4b2b492 100644
--- a/kernel/cgroup/misc.c
+++ b/kernel/cgroup/misc.c
@@ -171,6 +171,11 @@ int misc_cg_try_charge(enum misc_res_type type, struct misc_cg *cg,
 	return 0;
 
 err_charge:
+	for (j = i; j; j = parent_misc(j)) {
+		atomic_long_inc(&j->res[type].events);
+		cgroup_file_notify(&j->events_file);
+	}
+
 	for (j = cg; j != i; j = parent_misc(j))
 		misc_cg_cancel_charge(type, j, amount);
 	misc_cg_cancel_charge(type, i, amount);
@@ -335,6 +340,19 @@ static int misc_cg_capacity_show(struct seq_file *sf, void *v)
 	return 0;
 }
 
+static int misc_events_show(struct seq_file *sf, void *v)
+{
+	struct misc_cg *cg = css_misc(seq_css(sf));
+	unsigned long events, i;
+
+	for (i = 0; i < MISC_CG_RES_TYPES; i++) {
+		events = atomic_long_read(&cg->res[i].events);
+		if (READ_ONCE(misc_res_capacity[i]) || events)
+			seq_printf(sf, "%s.max %lu\n", misc_res_name[i], events);
+	}
+	return 0;
+}
+
 /* Misc cgroup interface files */
 static struct cftype misc_cg_files[] = {
 	{
@@ -353,6 +371,12 @@ static int misc_cg_capacity_show(struct seq_file *sf, void *v)
 		.seq_show = misc_cg_capacity_show,
 		.flags = CFTYPE_ONLY_ON_ROOT,
 	},
+	{
+		.name = "events",
+		.flags = CFTYPE_NOT_ON_ROOT,
+		.file_offset = offsetof(struct misc_cg, events_file),
+		.seq_show = misc_events_show,
+	},
 	{}
 };
 
-- 
1.8.3.1

[PATCH v4 2/3] misc_cgroup: remove error log to avoid log flood

[brookxu]

From: Chunguang Xu <brookxu@tencent.com>

In scenarios where containers are frequently created and deleted,
a large number of error logs maybe generated. The logs only show
which node is about to go over the max limit, not the node which
resource request failed. As misc.events has provided relevant
information, maybe we can remove this log.

Signed-off-by: Chunguang Xu <brookxu@tencent.com>
Reviewed-by: Michal Koutný <mkoutny@suse.com>
---
v4: update commit message.

 include/linux/misc_cgroup.h | 1 -
 kernel/cgroup/misc.c        | 7 -------
 2 files changed, 8 deletions(-)

diff --git a/include/linux/misc_cgroup.h b/include/linux/misc_cgroup.h
index 091f2d2..c238207 100644
--- a/include/linux/misc_cgroup.h
+++ b/include/linux/misc_cgroup.h
@@ -37,7 +37,6 @@ struct misc_res {
 	unsigned long max;
 	atomic_long_t usage;
 	atomic_long_t events;
-	bool failed;
 };
 
 /**
diff --git a/kernel/cgroup/misc.c b/kernel/cgroup/misc.c
index 4b2b492..fe3e8a0 100644
--- a/kernel/cgroup/misc.c
+++ b/kernel/cgroup/misc.c
@@ -157,13 +157,6 @@ int misc_cg_try_charge(enum misc_res_type type, struct misc_cg *cg,
 		new_usage = atomic_long_add_return(amount, &res->usage);
 		if (new_usage > READ_ONCE(res->max) ||
 		    new_usage > READ_ONCE(misc_res_capacity[type])) {
-			if (!res->failed) {
-				pr_info("cgroup: charge rejected by the misc controller for %s resource in ",
-					misc_res_name[type]);
-				pr_cont_cgroup_path(i->css.cgroup);
-				pr_cont("\n");
-				res->failed = true;
-			}
 			ret = -EBUSY;
 			goto err_charge;
 		}
-- 
1.8.3.1

[PATCH v4 2/3] misc_cgroup: remove error log to avoid log flood

[brookxu]

From: Chunguang Xu <brookxu-1Nz4purKYjRBDgjK7y7TUQ@public.gmane.org>

In scenarios where containers are frequently created and deleted,
a large number of error logs maybe generated. The logs only show
which node is about to go over the max limit, not the node which
resource request failed. As misc.events has provided relevant
information, maybe we can remove this log.

Signed-off-by: Chunguang Xu <brookxu-1Nz4purKYjRBDgjK7y7TUQ@public.gmane.org>
Reviewed-by: Michal Koutn√Ω <mkoutny-IBi9RG/b67k@public.gmane.org>
---
v4: update commit message.

 include/linux/misc_cgroup.h | 1 -
 kernel/cgroup/misc.c        | 7 -------
 2 files changed, 8 deletions(-)

diff --git a/include/linux/misc_cgroup.h b/include/linux/misc_cgroup.h
index 091f2d2..c238207 100644
--- a/include/linux/misc_cgroup.h
+++ b/include/linux/misc_cgroup.h
@@ -37,7 +37,6 @@ struct misc_res {
 	unsigned long max;
 	atomic_long_t usage;
 	atomic_long_t events;
-	bool failed;
 };
 
 /**
diff --git a/kernel/cgroup/misc.c b/kernel/cgroup/misc.c
index 4b2b492..fe3e8a0 100644
--- a/kernel/cgroup/misc.c
+++ b/kernel/cgroup/misc.c
@@ -157,13 +157,6 @@ int misc_cg_try_charge(enum misc_res_type type, struct misc_cg *cg,
 		new_usage = atomic_long_add_return(amount, &res->usage);
 		if (new_usage > READ_ONCE(res->max) ||
 		    new_usage > READ_ONCE(misc_res_capacity[type])) {
-			if (!res->failed) {
-				pr_info("cgroup: charge rejected by the misc controller for %s resource in ",
-					misc_res_name[type]);
-				pr_cont_cgroup_path(i->css.cgroup);
-				pr_cont("\n");
-				res->failed = true;
-			}
 			ret = -EBUSY;
 			goto err_charge;
 		}
-- 
1.8.3.1

[PATCH v4 3/3] docs/cgroup: add entry for misc.events

[brookxu]

From: Chunguang Xu <brookxu@tencent.com>

Added descriptions of misc.events.

Signed-off-by: Chunguang Xu <brookxu@tencent.com>
Reviewed-by: Michal Koutný <mkoutny@suse.com>
---
 Documentation/admin-guide/cgroup-v2.rst | 10 ++++++++++
 1 file changed, 10 insertions(+)

diff --git a/Documentation/admin-guide/cgroup-v2.rst b/Documentation/admin-guide/cgroup-v2.rst
index babbe04..e7acc55 100644
--- a/Documentation/admin-guide/cgroup-v2.rst
+++ b/Documentation/admin-guide/cgroup-v2.rst
@@ -2310,6 +2310,16 @@ Miscellaneous controller provides 3 interface files. If two misc resources (res_
         Limits can be set higher than the capacity value in the misc.capacity
         file.
 
+  misc.events
+	A read-only flat-keyed file which exists on non-root cgroups. The
+	following entries are defined. Unless specified otherwise, a value
+	change in this file generates a file modified event. All fields in
+	this file are hierarchical.
+
+	  max
+		The number of times the cgroup's resource usage was
+		about to go over the max boundary.
+
 Migration and Ownership
 ~~~~~~~~~~~~~~~~~~~~~~~
 
-- 
1.8.3.1

[PATCH v4 3/3] docs/cgroup: add entry for misc.events

[brookxu]

From: Chunguang Xu <brookxu@tencent.com>

Added descriptions of misc.events.

Signed-off-by: Chunguang Xu <brookxu@tencent.com>
Reviewed-by: Michal Koutn√Ω <mkoutny@suse.com>
---
 Documentation/admin-guide/cgroup-v2.rst | 10 ++++++++++
 1 file changed, 10 insertions(+)

diff --git a/Documentation/admin-guide/cgroup-v2.rst b/Documentation/admin-guide/cgroup-v2.rst
index babbe04..e7acc55 100644
--- a/Documentation/admin-guide/cgroup-v2.rst
+++ b/Documentation/admin-guide/cgroup-v2.rst
@@ -2310,6 +2310,16 @@ Miscellaneous controller provides 3 interface files. If two misc resources (res_
         Limits can be set higher than the capacity value in the misc.capacity
         file.
 
+  misc.events
+	A read-only flat-keyed file which exists on non-root cgroups. The
+	following entries are defined. Unless specified otherwise, a value
+	change in this file generates a file modified event. All fields in
+	this file are hierarchical.
+
+	  max
+		The number of times the cgroup's resource usage was
+		about to go over the max boundary.
+
 Migration and Ownership
 ~~~~~~~~~~~~~~~~~~~~~~~
 
-- 
1.8.3.1

Re: [PATCH v4 1/3] misc_cgroup: introduce misc.events to count failures

[Tejun Heo]

On Fri, Sep 17, 2021 at 08:44:14PM +0800, brookxu wrote:
> From: Chunguang Xu <brookxu@tencent.com>
> 
> Introduce misc.events to make it easier for us to understand
> the pressure of resources. Currently only the 'max' event is
> implemented, which indicates the times the resource is about
> to exceeds the max limit.
> 
> Signed-off-by: Chunguang Xu <brookxu@tencent.com>
> Reviewed-by: Vipin Sharma <vipinsh@google.com>
> Reviewed-by: Michal Koutný <mkoutny@suse.com>

Applied 1-3 to cgroup/for-5.16.

Thanks.

-- 
tejun