Andrey Ryabinin [off-list ref] writes:

 static int cpuacct_stats_show(struct seq_file *sf, void *v)
 {

        ...

 	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.sum_exec_runtime += *per_cpu_ptr(ca->cpuusage, cpu);

Or the stats can all be 0...