Commit 5a1c9558 authored by Frederic Weisbecker's avatar Frederic Weisbecker Committed by Ingo Molnar
Browse files

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: default avatarFrederic Weisbecker <frederic@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Wanpeng Li <wanpengli@tencent.com>
Cc: Yauheni Kaliuta <yauheni.kaliuta@redhat.com>
Link: https://lkml.kernel.org/r/20191121024430.19938-2-frederic@kernel.org


Signed-off-by: default avatarIngo Molnar <mingo@kernel.org>
parent bef69dd8

kernel/sched/cputime.c

+43 −11
Original line number Diff line number Diff line
@@ -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];



		/*

		 * 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)

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