[PATCH 4/4] sched/cpuacct: Make user/system times in cpuacct.stat more precise

[Andrey Ryabinin]

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 <a...@yandex-team.com>
---
 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 7eff79faab0d..36347f2810c0 100644
--- a/kernel/sched/cpuacct.c
+++ b/kernel/sched/cpuacct.c
@@ -266,25 +266,30 @@ 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 += this_cpu_read(*ca->cpuusage);
        }
 
+       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;
-- 
2.26.2