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Diffstat (limited to 'kernel')
-rw-r--r--kernel/sched/cputime.c18
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);