From: Hiroshi Shimamoto <h-shimam...@ct.jp.nec.com>
/proc/stats shows invalid gtime when the thread is running in guest.
When vtime accounting is not enabled, we cannot get a valid delta.
The delta is calculated now - tsk->vtime_snap, but tsk->vtime_snap
is only updated when vtime accounting is enabled.
This patch makes task_gtime() just return gtime when vtime accounting
is not enabled.
The kernel config contains CONFIG_VIRT_CPU_ACCOUNTING_GEN=y and
CONFIG_NO_HZ_FULL_ALL=n and boot without nohz_full.
I ran and stop a busy loop in VM and see the gtime in host.
Dump the 43rd field which shows the gtime in every second.
# while :; do awk '{print $3" "$43}' /proc/3955/task/4014/stat; sleep 1; done
S 4348
R 7064566
R 7064766
R 7064967
R 7065168
S 4759
S 4759
During running busy loop, it returns large value.
After applying this patch, we can see right gtime.
# while :; do awk '{print $3" "$43}' /proc/10913/task/10956/stat; sleep 1; done
S 5338
R 5365
R 5465
R 5566
R 5666
S 5726
S 5726
Signed-off-by: Hiroshi Shimamoto <h-shimam...@ct.jp.nec.com>
---
kernel/sched/cputime.c | 3 +++
1 file changed, 3 insertions(+)
diff --git a/kernel/sched/cputime.c b/kernel/sched/cputime.c
index 8cbc3db..f614ee9 100644
--- a/kernel/sched/cputime.c
+++ b/kernel/sched/cputime.c
@@ -786,6 +786,9 @@ cputime_t task_gtime(struct task_struct *t)
unsigned int seq;
cputime_t gtime;
+ if (!vtime_accounting_enabled())
+ return t->gtime;
+
do {
seq = read_seqbegin(&t->vtime_seqlock);
--
1.8.3.1
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