[PATCH v2 5/5] sched/cpuacct: Make user/system times in cpuacct.stat more precise

From: Andrey Ryabinin
Date: Fri Aug 20 2021 - 05:42:05 EST


From: Andrey Ryabinin <arb@xxxxxxxxxxxxxxx>

cpuacct.stat shows user time based on raw random precision tick
based counters. Use cputime_addjust() to scale these values against the
total runtime accounted by the scheduler, like we already do
for user/system times in /proc/<pid>/stat.

Signed-off-by: Andrey Ryabinin <arb@xxxxxxxxxxxxxxx>
---
Changes since v1:
- fix cputime.sum_exec_runtime calculation
---
kernel/sched/cpuacct.c | 25 +++++++++++++++----------
1 file changed, 15 insertions(+), 10 deletions(-)

diff --git a/kernel/sched/cpuacct.c b/kernel/sched/cpuacct.c
index 9de7dd51beb0..3d06c5e4220d 100644
--- a/kernel/sched/cpuacct.c
+++ b/kernel/sched/cpuacct.c
@@ -261,25 +261,30 @@ static int cpuacct_all_seq_show(struct seq_file *m, void *V)
static int cpuacct_stats_show(struct seq_file *sf, void *v)
{
struct cpuacct *ca = css_ca(seq_css(sf));
- s64 val[CPUACCT_STAT_NSTATS];
+ struct task_cputime cputime;
+ u64 val[CPUACCT_STAT_NSTATS];
int cpu;
int stat;

- memset(val, 0, sizeof(val));
+ memset(&cputime, 0, sizeof(cputime));
for_each_possible_cpu(cpu) {
u64 *cpustat = per_cpu_ptr(ca->cpustat, cpu)->cpustat;

- val[CPUACCT_STAT_USER] += cpustat[CPUTIME_USER];
- val[CPUACCT_STAT_USER] += cpustat[CPUTIME_NICE];
- val[CPUACCT_STAT_SYSTEM] += cpustat[CPUTIME_SYSTEM];
- val[CPUACCT_STAT_SYSTEM] += cpustat[CPUTIME_IRQ];
- val[CPUACCT_STAT_SYSTEM] += cpustat[CPUTIME_SOFTIRQ];
+ cputime.utime += cpustat[CPUTIME_USER];
+ cputime.utime += cpustat[CPUTIME_NICE];
+ cputime.stime += cpustat[CPUTIME_SYSTEM];
+ cputime.stime += cpustat[CPUTIME_IRQ];
+ cputime.stime += cpustat[CPUTIME_SOFTIRQ];
+
+ cputime.sum_exec_runtime += *per_cpu_ptr(ca->cpuusage, cpu);
}

+ cputime_adjust(&cputime, &seq_css(sf)->cgroup->prev_cputime,
+ &val[CPUACCT_STAT_USER], &val[CPUACCT_STAT_SYSTEM]);
+
for (stat = 0; stat < CPUACCT_STAT_NSTATS; stat++) {
- seq_printf(sf, "%s %lld\n",
- cpuacct_stat_desc[stat],
- (long long)nsec_to_clock_t(val[stat]));
+ seq_printf(sf, "%s %llu\n", cpuacct_stat_desc[stat],
+ nsec_to_clock_t(val[stat]));
}

return 0;
--
2.31.1