Now that cpu serves the same files as cpuacct and using cpuacct
separately from cpu is deprecated, we can deprecate cpuacct. To avoid
disturbing userland which has been co-mounting cpu and cpuacct,
implement some hackery in cgroup core so that cpuacct co-mounting
still works even if cpuacct is disabled.
The goal of this patch is to accelerate disabling and removal of
cpuacct by decoupling kernel-side deprecation from userland changes.
Userland is recommended to do the following.
* If /proc/cgroups lists cpuacct, always co-mount it with cpu under
e.g. /sys/fs/cgroup/cpu.
* Optionally create symlinks for compatibility -
e.g. /sys/fs/cgroup/cpuacct and /sys/fs/cgroup/cpu,cpucct both
pointing to /sys/fs/cgroup/cpu - whether cpuacct exists or not.
This compatibility hack will eventually go away.
Signed-off-by: Tejun Heo <tj@xxxxxxxxxx>
Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
Cc: Glauber Costa <glommer@xxxxxxxxxxxxx>
Cc: Michal Hocko <mhocko@xxxxxxx>
Cc: Kay Sievers <kay.sievers@xxxxxxxx>
Cc: Lennart Poettering <mzxreary@xxxxxxxxxxx>
Cc: Dave Jones <davej@xxxxxxxxxx>
Cc: Ben Hutchings <ben@xxxxxxxxxxxxxxx>
Cc: Paul Turner <pjt@xxxxxxxxxx>
---
init/Kconfig | 11 ++++++++++-
kernel/cgroup.c | 41 +++++++++++++++++++++++++++++++++++++++--
kernel/sched/core.c | 2 ++
3 files changed, 51 insertions(+), 3 deletions(-)
diff --git a/init/Kconfig b/init/Kconfig
index af6c7f8..a13cf8f 100644
--- a/init/Kconfig
+++ b/init/Kconfig
@@ -675,11 +675,20 @@ config PROC_PID_CPUSET
default y
config CGROUP_CPUACCT
- bool "Simple CPU accounting cgroup subsystem"
+ bool "DEPRECATED: Simple CPU accounting cgroup subsystem"
+ default n
help
Provides a simple Resource Controller for monitoring the
total CPU consumed by the tasks in a cgroup.
+ This cgroup subsystem is deprecated. The CPU cgroup
+ subsystem serves the same accounting files and "cpuacct"
+ mount option is ignored if specified with "cpu". As long as
+ userland co-mounts cpu and cpuacct, disabling this
+ controller should be mostly unnoticeable - one notable
+ difference is that /proc/PID/cgroup won't list cpuacct
+ anymore.
+
config RESOURCE_COUNTERS
bool "Resource counters"
help
diff --git a/kernel/cgroup.c b/kernel/cgroup.c
index 01c11e3..a577f6c 100644
--- a/kernel/cgroup.c
+++ b/kernel/cgroup.c
@@ -1157,6 +1157,7 @@ static int parse_cgroupfs_options(char *data, struct cgroup_sb_opts *opts)
unsigned long mask = (unsigned long)-1;
int i;
bool module_pin_failed = false;
+ bool cpuacct_requested = false;
BUG_ON(!mutex_is_locked(&cgroup_mutex));
@@ -1242,8 +1243,13 @@ static int parse_cgroupfs_options(char *data, struct cgroup_sb_opts *opts)
break;
}
- if (i == CGROUP_SUBSYS_COUNT)
+ /* handle deprecated cpuacct specially, see below */
+ if (!strcmp(token, "cpuacct")) {
+ cpuacct_requested = true;
+ one_ss = true;
+ } else if (i == CGROUP_SUBSYS_COUNT) {
return -ENOENT;
+ }
}
/*
@@ -1270,8 +1276,25 @@ static int parse_cgroupfs_options(char *data, struct cgroup_sb_opts *opts)
* this creates some discrepancies in /proc/cgroups and
* /proc/PID/cgroup.
*
+ * Accept and ignore "cpuacct" option if comounted with "cpu" even
+ * when cpuacct itself is disabled to allow quick disabling and
+ * removal of cpuacct. This will be removed eventually.
+ *
* https://lkml.org/lkml/2012/9/13/542
*/
+ if (cpuacct_requested) {
+ bool comounted = false;
+
+#if IS_ENABLED(CONFIG_CGROUP_SCHED)
+ comounted = opts->subsys_bits & (1 << cpu_cgroup_subsys_id);
+#endif
+ if (!comounted) {
+ pr_warning("cgroup: mounting cpuacct separately from cpu is deprecated\n");
+#if !IS_ENABLED(CONFIG_CGROUP_CPUACCT)
+ return -EINVAL;
+#endif
+ }
+ }
#if IS_ENABLED(CONFIG_CGROUP_SCHED) && IS_ENABLED(CONFIG_CGROUP_CPUACCT)
if ((opts->subsys_bits & (1 << cpu_cgroup_subsys_id)) &&
(opts->subsys_bits & (1 << cpuacct_subsys_id)))
@@ -4678,6 +4701,7 @@ const struct file_operations proc_cgroup_operations = {
/* Display information about each subsystem and each hierarchy */
static int proc_cgroupstats_show(struct seq_file *m, void *v)
{
+ struct cgroup_subsys *ss;
int i;
seq_puts(m, "#subsys_name\thierarchy\tnum_cgroups\tenabled\n");
@@ -4688,7 +4712,7 @@ static int proc_cgroupstats_show(struct seq_file *m, void *v)
*/
mutex_lock(&cgroup_mutex);
for (i = 0; i < CGROUP_SUBSYS_COUNT; i++) {
- struct cgroup_subsys *ss = subsys[i];
+ ss = subsys[i];
if (ss == NULL)
continue;
seq_printf(m, "%s\t%d\t%d\t%d\n",
@@ -4696,6 +4720,19 @@ static int proc_cgroupstats_show(struct seq_file *m, void *v)
ss->root->number_of_cgroups, !ss->disabled);
}
mutex_unlock(&cgroup_mutex);
+
+ /*
+ * Fake /proc/cgroups entry for cpuacct to trick userland into
+ * cpu,cpuacct comounts. This is to allow quick disabling and
+ * removal of cpuacct and will be removed eventually.
+ */
+#if IS_ENABLED(CONFIG_CGROUP_SCHED) && !IS_ENABLED(CONFIG_CGROUP_CPUACCT)
+ ss = subsys[cpu_cgroup_subsys_id];
+ if (ss) {
+ seq_printf(m, "cpuacct\t%d\t%d\t%d\n", ss->root->hierarchy_id,
+ ss->root->number_of_cgroups, !ss->disabled);
+ }
+#endif
return 0;
}
diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index 9648671..10176a3 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -8569,6 +8569,8 @@ struct cgroup_subsys cpu_cgroup_subsys = {
#ifdef CONFIG_CGROUP_CPUACCT
+#warning CONFIG_CGROUP_CPUACCT is deprecated, read the Kconfig help message
+
/*
* CPU accounting code for task groups.
*
--
1.7.7.3
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