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cgroup: add cpu.stat file to root cgroup

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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@bur.io>
Suggested-by: Tejun Heo <tj@kernel.org>
Signed-off-by: Tejun Heo <tj@kernel.org>
This commit is contained in:
Boris Burkov
2020-05-27 14:43:19 -07:00
committed by Tejun Heo
parent 6b6ebb3474
commit 936f2a70f2
3 changed files with 53 additions and 12 deletions
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58
kernel/cgroup/rstat.c
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@@ -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;
struct task_cputime cputime;
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();
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);