diff options
| -rw-r--r-- | kernel/sched/cputime.c | 18 |
1 files changed, 15 insertions, 3 deletions
diff --git a/kernel/sched/cputime.c b/kernel/sched/cputime.c index 2ee83b200504..a846cf89eb96 100644 --- a/kernel/sched/cputime.c +++ b/kernel/sched/cputime.c @@ -263,6 +263,11 @@ void account_idle_time(cputime_t cputime) cpustat[CPUTIME_IDLE] += (__force u64) cputime; } +/* + * When a guest is interrupted for a longer amount of time, missed clock + * ticks are not redelivered later. Due to that, this function may on + * occasion account more time than the calling functions think elapsed. + */ static __always_inline cputime_t steal_account_process_time(cputime_t maxtime) { #ifdef CONFIG_PARAVIRT @@ -371,7 +376,7 @@ static void irqtime_account_process_tick(struct task_struct *p, int user_tick, * idle, or potentially user or system time. Due to rounding, * other time can exceed ticks occasionally. */ - other = account_other_time(cputime); + other = account_other_time(ULONG_MAX); if (other >= cputime) return; cputime -= other; @@ -486,7 +491,7 @@ void account_process_tick(struct task_struct *p, int user_tick) } cputime = cputime_one_jiffy; - steal = steal_account_process_time(cputime); + steal = steal_account_process_time(ULONG_MAX); if (steal >= cputime) return; @@ -516,7 +521,7 @@ void account_idle_ticks(unsigned long ticks) } cputime = jiffies_to_cputime(ticks); - steal = steal_account_process_time(cputime); + steal = steal_account_process_time(ULONG_MAX); if (steal >= cputime) return; @@ -699,6 +704,13 @@ static cputime_t get_vtime_delta(struct task_struct *tsk) unsigned long now = READ_ONCE(jiffies); cputime_t delta, other; + /* + * Unlike tick based timing, vtime based timing never has lost + * ticks, and no need for steal time accounting to make up for + * lost ticks. Vtime accounts a rounded version of actual + * elapsed time. Limit account_other_time to prevent rounding + * errors from causing elapsed vtime to go negative. + */ delta = jiffies_to_cputime(now - tsk->vtime_snap); other = account_other_time(delta); WARN_ON_ONCE(tsk->vtime_snap_whence == VTIME_INACTIVE); |