Currently, the root cgroup does not have a cpu.stat file. Add one which
is consistent with /proc/stat to capture global cpu statistics that
might not fall under cgroup accounting.
We haven't done this in the past because the data are already presented
in /proc/stat and we didn't want to add overhead from collecting root
cgroup stats when cgroups are configured, but no cgroups have been
created.
By keeping the data consistent with /proc/stat, I think we avoid the
first problem, while improving the usability of cgroups stats.
We avoid the second problem by computing the contents of cpu.stat from
existing data collected for /proc/stat anyway.
Signed-off-by: Boris Burkov <boris@xxxxxx>
Suggested-by: Tejun Heo <tj@xxxxxxxxxx>
---
kernel/cgroup/cgroup.c | 1 -
kernel/cgroup/rstat.c | 60 ++++++++++++++++++++++++++++++++++++------
2 files changed, 52 insertions(+), 9 deletions(-)
diff --git a/kernel/cgroup/cgroup.c b/kernel/cgroup/cgroup.c
index 557a9b9d2244..b8a75169c3e4 100644
--- a/kernel/cgroup/cgroup.c
+++ b/kernel/cgroup/cgroup.c
@@ -4881,7 +4881,6 @@ static struct cftype cgroup_base_files[] = {
},
{
.name = "cpu.stat",
- .flags = CFTYPE_NOT_ON_ROOT,
.seq_show = cpu_stat_show,
},
#ifdef CONFIG_PSI
diff --git a/kernel/cgroup/rstat.c b/kernel/cgroup/rstat.c
index 41ca996568df..b6397a186ce9 100644
--- a/kernel/cgroup/rstat.c
+++ b/kernel/cgroup/rstat.c
@@ -389,18 +389,62 @@ void __cgroup_account_cputime_field(struct cgroup *cgrp,
cgroup_base_stat_cputime_account_end(cgrp, rstatc);
}
+/*
+ * compute the cputime for the root cgroup by getting the per cpu data
+ * at a global level, then categorizing the fields in a manner consistent
+ * with how it is done by __cgroup_account_cputime_field for each bit of
+ * cpu time attributed to a cgroup.
+ */
+static void root_cgroup_cputime(struct task_cputime *cputime)
+{
+ int i;
+
+ cputime->stime = 0;
+ cputime->utime = 0;
+ cputime->sum_exec_runtime = 0;
+ for_each_possible_cpu(i) {
+ struct kernel_cpustat kcpustat;
+ u64 *cpustat = kcpustat.cpustat;
+ u64 user = 0;
+ u64 sys = 0;
+
+ kcpustat_cpu_fetch(&kcpustat, i);
+
+ user += cpustat[CPUTIME_USER];
+ user += cpustat[CPUTIME_NICE];
+ cputime->utime += user;
+
+ sys += cpustat[CPUTIME_SYSTEM];
+ sys += cpustat[CPUTIME_IRQ];
+ sys += cpustat[CPUTIME_SOFTIRQ];
+ cputime->stime += sys;
+
+ cputime->sum_exec_runtime += user;
+ cputime->sum_exec_runtime += sys;
+ cputime->sum_exec_runtime += cpustat[CPUTIME_STEAL];
+ cputime->sum_exec_runtime += cpustat[CPUTIME_GUEST];
+ cputime->sum_exec_runtime += cpustat[CPUTIME_GUEST_NICE];
+ }
+}
+
void cgroup_base_stat_cputime_show(struct seq_file *seq)
{
struct cgroup *cgrp = seq_css(seq)->cgroup;
u64 usage, utime, stime;
-
- if (!cgroup_parent(cgrp))
- return;
-
- cgroup_rstat_flush_hold(cgrp);
- usage = cgrp->bstat.cputime.sum_exec_runtime;
- cputime_adjust(&cgrp->bstat.cputime, &cgrp->prev_cputime, &utime, &stime);
- cgroup_rstat_flush_release();
+ struct task_cputime cputime;
+
+ if (cgroup_parent(cgrp)) {
+ cgroup_rstat_flush_hold(cgrp);
+ usage = cgrp->bstat.cputime.sum_exec_runtime;
+ cputime_adjust(&cgrp->bstat.cputime, &cgrp->prev_cputime,
+ &utime, &stime);
+ cgroup_rstat_flush_release();
+ } else {
+ root_cgroup_cputime(&cputime);
+ usage = cputime.sum_exec_runtime;
+ utime = cputime.utime;
+ stime = cputime.stime;
+ }
do_div(usage, NSEC_PER_USEC);
do_div(utime, NSEC_PER_USEC);
--
2.24.1
