The dyntick-idle steal time is currently accounted when the tick restarts but the stolen idle time is not substracted from the idle time that was already accounted. This is to avoid observing the idle time going backward as the dyntick-idle cputime accessors can't reliably know in advance the stolen idle time.
In order to maintain a forward progressing idle cputime while substracting idle steal time from it, keep track of the previously accounted idle stolen time and substract it from _later_ idle cputime accounting. Signed-off-by: Frederic Weisbecker <[email protected]> --- include/linux/kernel_stat.h | 1 + kernel/sched/cputime.c | 9 ++++++++- 2 files changed, 9 insertions(+), 1 deletion(-) diff --git a/include/linux/kernel_stat.h b/include/linux/kernel_stat.h index e59916477075..a5b5a25c3cc1 100644 --- a/include/linux/kernel_stat.h +++ b/include/linux/kernel_stat.h @@ -39,6 +39,7 @@ struct kernel_cpustat { bool idle_elapse; seqcount_t idle_sleeptime_seq; ktime_t idle_entrytime; + u64 idle_steal; #endif u64 cpustat[NR_STATS]; }; diff --git a/kernel/sched/cputime.c b/kernel/sched/cputime.c index 3dadfaa92b27..749a6ed4d2fa 100644 --- a/kernel/sched/cputime.c +++ b/kernel/sched/cputime.c @@ -424,18 +424,25 @@ static void kcpustat_idle_stop(struct kernel_cpustat *kc, ktime_t now) { u64 *cpustat = kc->cpustat; ktime_t delta; + u64 steal, steal_delta; if (!kc->idle_elapse) return; delta = ktime_sub(now, kc->idle_entrytime); + steal = steal_account_process_time(delta); write_seqcount_begin(&kc->idle_sleeptime_seq); + steal_delta = min_t(u64, kc->idle_steal, delta); + delta -= steal_delta; + kc->idle_steal -= steal_delta; + if (nr_iowait_cpu(smp_processor_id()) > 0) cpustat[CPUTIME_IOWAIT] = ktime_add(cpustat[CPUTIME_IOWAIT], delta); else cpustat[CPUTIME_IDLE] = ktime_add(cpustat[CPUTIME_IDLE], delta); + kc->idle_steal += steal; kc->idle_entrytime = now; kc->idle_elapse = false; write_seqcount_end(&kc->idle_sleeptime_seq); @@ -459,7 +466,6 @@ void kcpustat_dyntick_stop(ktime_t now) kc->idle_dyntick = false; irqtime_dyntick_stop(); vtime_dyntick_stop(); - steal_account_process_time(ULONG_MAX); } } @@ -507,6 +513,7 @@ static u64 kcpustat_field_dyntick(int cpu, enum cpu_usage_stat idx, if (kc->idle_elapse && compute_delta) { ktime_t delta = ktime_sub(now, kc->idle_entrytime); + delta -= min_t(u64, kc->idle_steal, (u64)delta); idle = ktime_add(cpustat[idx], delta); } else { idle = cpustat[idx]; -- 2.51.1
