The following commit has been merged into the sched/core branch of tip:
Commit-ID: 5a1c95580f1d89c8a736bb02ecd82a8858388b8a
Gitweb: https://git.kernel.org/tip/5a1c95580f1d89c8a736bb02ecd82a8858388b8a
Author: Frederic Weisbecker <frederic@xxxxxxxxxx>
AuthorDate: Thu, 21 Nov 2019 03:44:25 +01:00
Committer: Ingo Molnar <mingo@xxxxxxxxxx>
CommitterDate: Thu, 21 Nov 2019 07:33:23 +01:00
sched/cputime: Support other fields on kcpustat_field()
Provide support for user, nice, guest and guest_nice fields through
kcpustat_field().
Whether we account the delta to a nice or not nice field is decided on
top of the nice value snapshot taken at the time we call kcpustat_field().
If the nice value of the task has been changed since the last vtime
update, we may have inacurrate distribution of the nice VS unnice
cputime.
However this is considered as a minor issue compared to the proper fix
that would involve interrupting the target on nice updates, which is
undesired on nohz_full CPUs.
Signed-off-by: Frederic Weisbecker <frederic@xxxxxxxxxx>
Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
Cc: Wanpeng Li <wanpengli@xxxxxxxxxxx>
Cc: Yauheni Kaliuta <yauheni.kaliuta@xxxxxxxxxx>
Link: https://lkml.kernel.org/r/20191121024430.19938-2-frederic@xxxxxxxxxx
Signed-off-by: Ingo Molnar <mingo@xxxxxxxxxx>
---
kernel/sched/cputime.c | 54 ++++++++++++++++++++++++++++++++---------
1 file changed, 43 insertions(+), 11 deletions(-)
diff --git a/kernel/sched/cputime.c b/kernel/sched/cputime.c
index e0cd206..27b5406 100644
--- a/kernel/sched/cputime.c
+++ b/kernel/sched/cputime.c
@@ -912,11 +912,21 @@ void task_cputime(struct task_struct *t, u64 *utime, u64 *stime)
} while (read_seqcount_retry(&vtime->seqcount, seq));
}
+static u64 kcpustat_user_vtime(struct vtime *vtime)
+{
+ if (vtime->state == VTIME_USER)
+ return vtime->utime + vtime_delta(vtime);
+ else if (vtime->state == VTIME_GUEST)
+ return vtime->gtime + vtime_delta(vtime);
+ return 0;
+}
+
static int kcpustat_field_vtime(u64 *cpustat,
- struct vtime *vtime,
+ struct task_struct *tsk,
enum cpu_usage_stat usage,
int cpu, u64 *val)
{
+ struct vtime *vtime = &tsk->vtime;
unsigned int seq;
int err;
@@ -946,9 +956,37 @@ static int kcpustat_field_vtime(u64 *cpustat,
*val = cpustat[usage];
- if (vtime->state == VTIME_SYS)
- *val += vtime->stime + vtime_delta(vtime);
-
+ /*
+ * Nice VS unnice cputime accounting may be inaccurate if
+ * the nice value has changed since the last vtime update.
+ * But proper fix would involve interrupting target on nice
+ * updates which is a no go on nohz_full (although the scheduler
+ * may still interrupt the target if rescheduling is needed...)
+ */
+ switch (usage) {
+ case CPUTIME_SYSTEM:
+ if (vtime->state == VTIME_SYS)
+ *val += vtime->stime + vtime_delta(vtime);
+ break;
+ case CPUTIME_USER:
+ if (task_nice(tsk) <= 0)
+ *val += kcpustat_user_vtime(vtime);
+ break;
+ case CPUTIME_NICE:
+ if (task_nice(tsk) > 0)
+ *val += kcpustat_user_vtime(vtime);
+ break;
+ case CPUTIME_GUEST:
+ if (vtime->state == VTIME_GUEST && task_nice(tsk) <= 0)
+ *val += vtime->gtime + vtime_delta(vtime);
+ break;
+ case CPUTIME_GUEST_NICE:
+ if (vtime->state == VTIME_GUEST && task_nice(tsk) > 0)
+ *val += vtime->gtime + vtime_delta(vtime);
+ break;
+ default:
+ break;
+ }
} while (read_seqcount_retry(&vtime->seqcount, seq));
return 0;
@@ -965,15 +1003,10 @@ u64 kcpustat_field(struct kernel_cpustat *kcpustat,
if (!vtime_accounting_enabled_cpu(cpu))
return cpustat[usage];
- /* Only support sys vtime for now */
- if (usage != CPUTIME_SYSTEM)
- return cpustat[usage];
-
rq = cpu_rq(cpu);
for (;;) {
struct task_struct *curr;
- struct vtime *vtime;
rcu_read_lock();
curr = rcu_dereference(rq->curr);
@@ -982,8 +1015,7 @@ u64 kcpustat_field(struct kernel_cpustat *kcpustat,
return cpustat[usage];
}
- vtime = &curr->vtime;
- err = kcpustat_field_vtime(cpustat, vtime, usage, cpu, &val);
+ err = kcpustat_field_vtime(cpustat, curr, usage, cpu, &val);
rcu_read_unlock();
if (!err)
|