diff options
Diffstat (limited to 'kernel/sched/cputime.c')
| -rw-r--r-- | kernel/sched/cputime.c | 1102 |
1 files changed, 1102 insertions, 0 deletions
diff --git a/kernel/sched/cputime.c b/kernel/sched/cputime.c new file mode 100644 index 0000000000..af7952f12e --- /dev/null +++ b/kernel/sched/cputime.c @@ -0,0 +1,1102 @@ +// SPDX-License-Identifier: GPL-2.0-only +/* + * Simple CPU accounting cgroup controller + */ + +#ifdef CONFIG_VIRT_CPU_ACCOUNTING_NATIVE + #include <asm/cputime.h> +#endif + +#ifdef CONFIG_IRQ_TIME_ACCOUNTING + +/* + * There are no locks covering percpu hardirq/softirq time. + * They are only modified in vtime_account, on corresponding CPU + * with interrupts disabled. So, writes are safe. + * They are read and saved off onto struct rq in update_rq_clock(). + * This may result in other CPU reading this CPU's irq time and can + * race with irq/vtime_account on this CPU. We would either get old + * or new value with a side effect of accounting a slice of irq time to wrong + * task when irq is in progress while we read rq->clock. That is a worthy + * compromise in place of having locks on each irq in account_system_time. + */ +DEFINE_PER_CPU(struct irqtime, cpu_irqtime); + +static int sched_clock_irqtime; + +void enable_sched_clock_irqtime(void) +{ + sched_clock_irqtime = 1; +} + +void disable_sched_clock_irqtime(void) +{ + sched_clock_irqtime = 0; +} + +static void irqtime_account_delta(struct irqtime *irqtime, u64 delta, + enum cpu_usage_stat idx) +{ + u64 *cpustat = kcpustat_this_cpu->cpustat; + + u64_stats_update_begin(&irqtime->sync); + cpustat[idx] += delta; + irqtime->total += delta; + irqtime->tick_delta += delta; + u64_stats_update_end(&irqtime->sync); +} + +/* + * Called after incrementing preempt_count on {soft,}irq_enter + * and before decrementing preempt_count on {soft,}irq_exit. + */ +void irqtime_account_irq(struct task_struct *curr, unsigned int offset) +{ + struct irqtime *irqtime = this_cpu_ptr(&cpu_irqtime); + unsigned int pc; + s64 delta; + int cpu; + + if (!sched_clock_irqtime) + return; + + cpu = smp_processor_id(); + delta = sched_clock_cpu(cpu) - irqtime->irq_start_time; + irqtime->irq_start_time += delta; + pc = irq_count() - offset; + + /* + * We do not account for softirq time from ksoftirqd here. + * We want to continue accounting softirq time to ksoftirqd thread + * in that case, so as not to confuse scheduler with a special task + * that do not consume any time, but still wants to run. + */ + if (pc & HARDIRQ_MASK) + irqtime_account_delta(irqtime, delta, CPUTIME_IRQ); + else if ((pc & SOFTIRQ_OFFSET) && curr != this_cpu_ksoftirqd()) + irqtime_account_delta(irqtime, delta, CPUTIME_SOFTIRQ); +} + +static u64 irqtime_tick_accounted(u64 maxtime) +{ + struct irqtime *irqtime = this_cpu_ptr(&cpu_irqtime); + u64 delta; + + delta = min(irqtime->tick_delta, maxtime); + irqtime->tick_delta -= delta; + + return delta; +} + +#else /* CONFIG_IRQ_TIME_ACCOUNTING */ + +#define sched_clock_irqtime (0) + +static u64 irqtime_tick_accounted(u64 dummy) +{ + return 0; +} + +#endif /* !CONFIG_IRQ_TIME_ACCOUNTING */ + +static inline void task_group_account_field(struct task_struct *p, int index, + u64 tmp) +{ + /* + * Since all updates are sure to touch the root cgroup, we + * get ourselves ahead and touch it first. If the root cgroup + * is the only cgroup, then nothing else should be necessary. + * + */ + __this_cpu_add(kernel_cpustat.cpustat[index], tmp); + + cgroup_account_cputime_field(p, index, tmp); +} + +/* + * Account user CPU time to a process. + * @p: the process that the CPU time gets accounted to + * @cputime: the CPU time spent in user space since the last update + */ +void account_user_time(struct task_struct *p, u64 cputime) +{ + int index; + + /* Add user time to process. */ + p->utime += cputime; + account_group_user_time(p, cputime); + + index = (task_nice(p) > 0) ? CPUTIME_NICE : CPUTIME_USER; + + /* Add user time to cpustat. */ + task_group_account_field(p, index, cputime); + + /* Account for user time used */ + acct_account_cputime(p); +} + +/* + * Account guest CPU time to a process. + * @p: the process that the CPU time gets accounted to + * @cputime: the CPU time spent in virtual machine since the last update + */ +void account_guest_time(struct task_struct *p, u64 cputime) +{ + u64 *cpustat = kcpustat_this_cpu->cpustat; + + /* Add guest time to process. */ + p->utime += cputime; + account_group_user_time(p, cputime); + p->gtime += cputime; + + /* Add guest time to cpustat. */ + if (task_nice(p) > 0) { + task_group_account_field(p, CPUTIME_NICE, cputime); + cpustat[CPUTIME_GUEST_NICE] += cputime; + } else { + task_group_account_field(p, CPUTIME_USER, cputime); + cpustat[CPUTIME_GUEST] += cputime; + } +} + +/* + * Account system CPU time to a process and desired cpustat field + * @p: the process that the CPU time gets accounted to + * @cputime: the CPU time spent in kernel space since the last update + * @index: pointer to cpustat field that has to be updated + */ +void account_system_index_time(struct task_struct *p, + u64 cputime, enum cpu_usage_stat index) +{ + /* Add system time to process. */ + p->stime += cputime; + account_group_system_time(p, cputime); + + /* Add system time to cpustat. */ + task_group_account_field(p, index, cputime); + + /* Account for system time used */ + acct_account_cputime(p); +} + +/* + * Account system CPU time to a process. + * @p: the process that the CPU time gets accounted to + * @hardirq_offset: the offset to subtract from hardirq_count() + * @cputime: the CPU time spent in kernel space since the last update + */ +void account_system_time(struct task_struct *p, int hardirq_offset, u64 cputime) +{ + int index; + + if ((p->flags & PF_VCPU) && (irq_count() - hardirq_offset == 0)) { + account_guest_time(p, cputime); + return; + } + + if (hardirq_count() - hardirq_offset) + index = CPUTIME_IRQ; + else if (in_serving_softirq()) + index = CPUTIME_SOFTIRQ; + else + index = CPUTIME_SYSTEM; + + account_system_index_time(p, cputime, index); +} + +/* + * Account for involuntary wait time. + * @cputime: the CPU time spent in involuntary wait + */ +void account_steal_time(u64 cputime) +{ + u64 *cpustat = kcpustat_this_cpu->cpustat; + + cpustat[CPUTIME_STEAL] += cputime; +} + +/* + * Account for idle time. + * @cputime: the CPU time spent in idle wait + */ +void account_idle_time(u64 cputime) +{ + u64 *cpustat = kcpustat_this_cpu->cpustat; + struct rq *rq = this_rq(); + + if (atomic_read(&rq->nr_iowait) > 0) + cpustat[CPUTIME_IOWAIT] += cputime; + else + cpustat[CPUTIME_IDLE] += cputime; +} + + +#ifdef CONFIG_SCHED_CORE +/* + * Account for forceidle time due to core scheduling. + * + * REQUIRES: schedstat is enabled. + */ +void __account_forceidle_time(struct task_struct *p, u64 delta) +{ + __schedstat_add(p->stats.core_forceidle_sum, delta); + + task_group_account_field(p, CPUTIME_FORCEIDLE, delta); +} +#endif + +/* + * 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 u64 steal_account_process_time(u64 maxtime) +{ +#ifdef CONFIG_PARAVIRT + if (static_key_false(¶virt_steal_enabled)) { + u64 steal; + + steal = paravirt_steal_clock(smp_processor_id()); + steal -= this_rq()->prev_steal_time; + steal = min(steal, maxtime); + account_steal_time(steal); + this_rq()->prev_steal_time += steal; + + return steal; + } +#endif + return 0; +} + +/* + * Account how much elapsed time was spent in steal, irq, or softirq time. + */ +static inline u64 account_other_time(u64 max) +{ + u64 accounted; + + lockdep_assert_irqs_disabled(); + + accounted = steal_account_process_time(max); + + if (accounted < max) + accounted += irqtime_tick_accounted(max - accounted); + + return accounted; +} + +#ifdef CONFIG_64BIT +static inline u64 read_sum_exec_runtime(struct task_struct *t) +{ + return t->se.sum_exec_runtime; +} +#else +static u64 read_sum_exec_runtime(struct task_struct *t) +{ + u64 ns; + struct rq_flags rf; + struct rq *rq; + + rq = task_rq_lock(t, &rf); + ns = t->se.sum_exec_runtime; + task_rq_unlock(rq, t, &rf); + + return ns; +} +#endif + +/* + * Accumulate raw cputime values of dead tasks (sig->[us]time) and live + * tasks (sum on group iteration) belonging to @tsk's group. + */ +void thread_group_cputime(struct task_struct *tsk, struct task_cputime *times) +{ + struct signal_struct *sig = tsk->signal; + u64 utime, stime; + struct task_struct *t; + unsigned int seq, nextseq; + unsigned long flags; + + /* + * Update current task runtime to account pending time since last + * scheduler action or thread_group_cputime() call. This thread group + * might have other running tasks on different CPUs, but updating + * their runtime can affect syscall performance, so we skip account + * those pending times and rely only on values updated on tick or + * other scheduler action. + */ + if (same_thread_group(current, tsk)) + (void) task_sched_runtime(current); + + rcu_read_lock(); + /* Attempt a lockless read on the first round. */ + nextseq = 0; + do { + seq = nextseq; + flags = read_seqbegin_or_lock_irqsave(&sig->stats_lock, &seq); + times->utime = sig->utime; + times->stime = sig->stime; + times->sum_exec_runtime = sig->sum_sched_runtime; + + for_each_thread(tsk, t) { + task_cputime(t, &utime, &stime); + times->utime += utime; + times->stime += stime; + times->sum_exec_runtime += read_sum_exec_runtime(t); + } + /* If lockless access failed, take the lock. */ + nextseq = 1; + } while (need_seqretry(&sig->stats_lock, seq)); + done_seqretry_irqrestore(&sig->stats_lock, seq, flags); + rcu_read_unlock(); +} + +#ifdef CONFIG_IRQ_TIME_ACCOUNTING +/* + * Account a tick to a process and cpustat + * @p: the process that the CPU time gets accounted to + * @user_tick: is the tick from userspace + * @rq: the pointer to rq + * + * Tick demultiplexing follows the order + * - pending hardirq update + * - pending softirq update + * - user_time + * - idle_time + * - system time + * - check for guest_time + * - else account as system_time + * + * Check for hardirq is done both for system and user time as there is + * no timer going off while we are on hardirq and hence we may never get an + * opportunity to update it solely in system time. + * p->stime and friends are only updated on system time and not on irq + * softirq as those do not count in task exec_runtime any more. + */ +static void irqtime_account_process_tick(struct task_struct *p, int user_tick, + int ticks) +{ + u64 other, cputime = TICK_NSEC * ticks; + + /* + * When returning from idle, many ticks can get accounted at + * once, including some ticks of steal, irq, and softirq time. + * Subtract those ticks from the amount of time accounted to + * idle, or potentially user or system time. Due to rounding, + * other time can exceed ticks occasionally. + */ + other = account_other_time(ULONG_MAX); + if (other >= cputime) + return; + + cputime -= other; + + if (this_cpu_ksoftirqd() == p) { + /* + * ksoftirqd time do not get accounted in cpu_softirq_time. + * So, we have to handle it separately here. + * Also, p->stime needs to be updated for ksoftirqd. + */ + account_system_index_time(p, cputime, CPUTIME_SOFTIRQ); + } else if (user_tick) { + account_user_time(p, cputime); + } else if (p == this_rq()->idle) { + account_idle_time(cputime); + } else if (p->flags & PF_VCPU) { /* System time or guest time */ + account_guest_time(p, cputime); + } else { + account_system_index_time(p, cputime, CPUTIME_SYSTEM); + } +} + +static void irqtime_account_idle_ticks(int ticks) +{ + irqtime_account_process_tick(current, 0, ticks); +} +#else /* CONFIG_IRQ_TIME_ACCOUNTING */ +static inline void irqtime_account_idle_ticks(int ticks) { } +static inline void irqtime_account_process_tick(struct task_struct *p, int user_tick, + int nr_ticks) { } +#endif /* CONFIG_IRQ_TIME_ACCOUNTING */ + +/* + * Use precise platform statistics if available: + */ +#ifdef CONFIG_VIRT_CPU_ACCOUNTING_NATIVE + +# ifndef __ARCH_HAS_VTIME_TASK_SWITCH +void vtime_task_switch(struct task_struct *prev) +{ + if (is_idle_task(prev)) + vtime_account_idle(prev); + else + vtime_account_kernel(prev); + + vtime_flush(prev); + arch_vtime_task_switch(prev); +} +# endif + +void vtime_account_irq(struct task_struct *tsk, unsigned int offset) +{ + unsigned int pc = irq_count() - offset; + + if (pc & HARDIRQ_OFFSET) { + vtime_account_hardirq(tsk); + } else if (pc & SOFTIRQ_OFFSET) { + vtime_account_softirq(tsk); + } else if (!IS_ENABLED(CONFIG_HAVE_VIRT_CPU_ACCOUNTING_IDLE) && + is_idle_task(tsk)) { + vtime_account_idle(tsk); + } else { + vtime_account_kernel(tsk); + } +} + +void cputime_adjust(struct task_cputime *curr, struct prev_cputime *prev, + u64 *ut, u64 *st) +{ + *ut = curr->utime; + *st = curr->stime; +} + +void task_cputime_adjusted(struct task_struct *p, u64 *ut, u64 *st) +{ + *ut = p->utime; + *st = p->stime; +} +EXPORT_SYMBOL_GPL(task_cputime_adjusted); + +void thread_group_cputime_adjusted(struct task_struct *p, u64 *ut, u64 *st) +{ + struct task_cputime cputime; + + thread_group_cputime(p, &cputime); + + *ut = cputime.utime; + *st = cputime.stime; +} + +#else /* !CONFIG_VIRT_CPU_ACCOUNTING_NATIVE: */ + +/* + * Account a single tick of CPU time. + * @p: the process that the CPU time gets accounted to + * @user_tick: indicates if the tick is a user or a system tick + */ +void account_process_tick(struct task_struct *p, int user_tick) +{ + u64 cputime, steal; + + if (vtime_accounting_enabled_this_cpu()) + return; + + if (sched_clock_irqtime) { + irqtime_account_process_tick(p, user_tick, 1); + return; + } + + cputime = TICK_NSEC; + steal = steal_account_process_time(ULONG_MAX); + + if (steal >= cputime) + return; + + cputime -= steal; + + if (user_tick) + account_user_time(p, cputime); + else if ((p != this_rq()->idle) || (irq_count() != HARDIRQ_OFFSET)) + account_system_time(p, HARDIRQ_OFFSET, cputime); + else + account_idle_time(cputime); +} + +/* + * Account multiple ticks of idle time. + * @ticks: number of stolen ticks + */ +void account_idle_ticks(unsigned long ticks) +{ + u64 cputime, steal; + + if (sched_clock_irqtime) { + irqtime_account_idle_ticks(ticks); + return; + } + + cputime = ticks * TICK_NSEC; + steal = steal_account_process_time(ULONG_MAX); + + if (steal >= cputime) + return; + + cputime -= steal; + account_idle_time(cputime); +} + +/* + * Adjust tick based cputime random precision against scheduler runtime + * accounting. + * + * Tick based cputime accounting depend on random scheduling timeslices of a + * task to be interrupted or not by the timer. Depending on these + * circumstances, the number of these interrupts may be over or + * under-optimistic, matching the real user and system cputime with a variable + * precision. + * + * Fix this by scaling these tick based values against the total runtime + * accounted by the CFS scheduler. + * + * This code provides the following guarantees: + * + * stime + utime == rtime + * stime_i+1 >= stime_i, utime_i+1 >= utime_i + * + * Assuming that rtime_i+1 >= rtime_i. + */ +void cputime_adjust(struct task_cputime *curr, struct prev_cputime *prev, + u64 *ut, u64 *st) +{ + u64 rtime, stime, utime; + unsigned long flags; + + /* Serialize concurrent callers such that we can honour our guarantees */ + raw_spin_lock_irqsave(&prev->lock, flags); + rtime = curr->sum_exec_runtime; + + /* + * This is possible under two circumstances: + * - rtime isn't monotonic after all (a bug); + * - we got reordered by the lock. + * + * In both cases this acts as a filter such that the rest of the code + * can assume it is monotonic regardless of anything else. + */ + if (prev->stime + prev->utime >= rtime) + goto out; + + stime = curr->stime; + utime = curr->utime; + + /* + * If either stime or utime are 0, assume all runtime is userspace. + * Once a task gets some ticks, the monotonicity code at 'update:' + * will ensure things converge to the observed ratio. + */ + if (stime == 0) { + utime = rtime; + goto update; + } + + if (utime == 0) { + stime = rtime; + goto update; + } + + stime = mul_u64_u64_div_u64(stime, rtime, stime + utime); + +update: + /* + * Make sure stime doesn't go backwards; this preserves monotonicity + * for utime because rtime is monotonic. + * + * utime_i+1 = rtime_i+1 - stime_i + * = rtime_i+1 - (rtime_i - utime_i) + * = (rtime_i+1 - rtime_i) + utime_i + * >= utime_i + */ + if (stime < prev->stime) + stime = prev->stime; + utime = rtime - stime; + + /* + * Make sure utime doesn't go backwards; this still preserves + * monotonicity for stime, analogous argument to above. + */ + if (utime < prev->utime) { + utime = prev->utime; + stime = rtime - utime; + } + + prev->stime = stime; + prev->utime = utime; +out: + *ut = prev->utime; + *st = prev->stime; + raw_spin_unlock_irqrestore(&prev->lock, flags); +} + +void task_cputime_adjusted(struct task_struct *p, u64 *ut, u64 *st) +{ + struct task_cputime cputime = { + .sum_exec_runtime = p->se.sum_exec_runtime, + }; + + if (task_cputime(p, &cputime.utime, &cputime.stime)) + cputime.sum_exec_runtime = task_sched_runtime(p); + cputime_adjust(&cputime, &p->prev_cputime, ut, st); +} +EXPORT_SYMBOL_GPL(task_cputime_adjusted); + +void thread_group_cputime_adjusted(struct task_struct *p, u64 *ut, u64 *st) +{ + struct task_cputime cputime; + + thread_group_cputime(p, &cputime); + cputime_adjust(&cputime, &p->signal->prev_cputime, ut, st); +} +#endif /* !CONFIG_VIRT_CPU_ACCOUNTING_NATIVE */ + +#ifdef CONFIG_VIRT_CPU_ACCOUNTING_GEN +static u64 vtime_delta(struct vtime *vtime) +{ + unsigned long long clock; + + clock = sched_clock(); + if (clock < vtime->starttime) + return 0; + + return clock - vtime->starttime; +} + +static u64 get_vtime_delta(struct vtime *vtime) +{ + u64 delta = vtime_delta(vtime); + u64 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. + */ + other = account_other_time(delta); + WARN_ON_ONCE(vtime->state == VTIME_INACTIVE); + vtime->starttime += delta; + + return delta - other; +} + +static void vtime_account_system(struct task_struct *tsk, + struct vtime *vtime) +{ + vtime->stime += get_vtime_delta(vtime); + if (vtime->stime >= TICK_NSEC) { + account_system_time(tsk, irq_count(), vtime->stime); + vtime->stime = 0; + } +} + +static void vtime_account_guest(struct task_struct *tsk, + struct vtime *vtime) +{ + vtime->gtime += get_vtime_delta(vtime); + if (vtime->gtime >= TICK_NSEC) { + account_guest_time(tsk, vtime->gtime); + vtime->gtime = 0; + } +} + +static void __vtime_account_kernel(struct task_struct *tsk, + struct vtime *vtime) +{ + /* We might have scheduled out from guest path */ + if (vtime->state == VTIME_GUEST) + vtime_account_guest(tsk, vtime); + else + vtime_account_system(tsk, vtime); +} + +void vtime_account_kernel(struct task_struct *tsk) +{ + struct vtime *vtime = &tsk->vtime; + + if (!vtime_delta(vtime)) + return; + + write_seqcount_begin(&vtime->seqcount); + __vtime_account_kernel(tsk, vtime); + write_seqcount_end(&vtime->seqcount); +} + +void vtime_user_enter(struct task_struct *tsk) +{ + struct vtime *vtime = &tsk->vtime; + + write_seqcount_begin(&vtime->seqcount); + vtime_account_system(tsk, vtime); + vtime->state = VTIME_USER; + write_seqcount_end(&vtime->seqcount); +} + +void vtime_user_exit(struct task_struct *tsk) +{ + struct vtime *vtime = &tsk->vtime; + + write_seqcount_begin(&vtime->seqcount); + vtime->utime += get_vtime_delta(vtime); + if (vtime->utime >= TICK_NSEC) { + account_user_time(tsk, vtime->utime); + vtime->utime = 0; + } + vtime->state = VTIME_SYS; + write_seqcount_end(&vtime->seqcount); +} + +void vtime_guest_enter(struct task_struct *tsk) +{ + struct vtime *vtime = &tsk->vtime; + /* + * The flags must be updated under the lock with + * the vtime_starttime flush and update. + * That enforces a right ordering and update sequence + * synchronization against the reader (task_gtime()) + * that can thus safely catch up with a tickless delta. + */ + write_seqcount_begin(&vtime->seqcount); + vtime_account_system(tsk, vtime); + tsk->flags |= PF_VCPU; + vtime->state = VTIME_GUEST; + write_seqcount_end(&vtime->seqcount); +} +EXPORT_SYMBOL_GPL(vtime_guest_enter); + +void vtime_guest_exit(struct task_struct *tsk) +{ + struct vtime *vtime = &tsk->vtime; + + write_seqcount_begin(&vtime->seqcount); + vtime_account_guest(tsk, vtime); + tsk->flags &= ~PF_VCPU; + vtime->state = VTIME_SYS; + write_seqcount_end(&vtime->seqcount); +} +EXPORT_SYMBOL_GPL(vtime_guest_exit); + +void vtime_account_idle(struct task_struct *tsk) +{ + account_idle_time(get_vtime_delta(&tsk->vtime)); +} + +void vtime_task_switch_generic(struct task_struct *prev) +{ + struct vtime *vtime = &prev->vtime; + + write_seqcount_begin(&vtime->seqcount); + if (vtime->state == VTIME_IDLE) + vtime_account_idle(prev); + else + __vtime_account_kernel(prev, vtime); + vtime->state = VTIME_INACTIVE; + vtime->cpu = -1; + write_seqcount_end(&vtime->seqcount); + + vtime = ¤t->vtime; + + write_seqcount_begin(&vtime->seqcount); + if (is_idle_task(current)) + vtime->state = VTIME_IDLE; + else if (current->flags & PF_VCPU) + vtime->state = VTIME_GUEST; + else + vtime->state = VTIME_SYS; + vtime->starttime = sched_clock(); + vtime->cpu = smp_processor_id(); + write_seqcount_end(&vtime->seqcount); +} + +void vtime_init_idle(struct task_struct *t, int cpu) +{ + struct vtime *vtime = &t->vtime; + unsigned long flags; + + local_irq_save(flags); + write_seqcount_begin(&vtime->seqcount); + vtime->state = VTIME_IDLE; + vtime->starttime = sched_clock(); + vtime->cpu = cpu; + write_seqcount_end(&vtime->seqcount); + local_irq_restore(flags); +} + +u64 task_gtime(struct task_struct *t) +{ + struct vtime *vtime = &t->vtime; + unsigned int seq; + u64 gtime; + + if (!vtime_accounting_enabled()) + return t->gtime; + + do { + seq = read_seqcount_begin(&vtime->seqcount); + + gtime = t->gtime; + if (vtime->state == VTIME_GUEST) + gtime += vtime->gtime + vtime_delta(vtime); + + } while (read_seqcount_retry(&vtime->seqcount, seq)); + + return gtime; +} + +/* + * Fetch cputime raw values from fields of task_struct and + * add up the pending nohz execution time since the last + * cputime snapshot. + */ +bool task_cputime(struct task_struct *t, u64 *utime, u64 *stime) +{ + struct vtime *vtime = &t->vtime; + unsigned int seq; + u64 delta; + int ret; + + if (!vtime_accounting_enabled()) { + *utime = t->utime; + *stime = t->stime; + return false; + } + + do { + ret = false; + seq = read_seqcount_begin(&vtime->seqcount); + + *utime = t->utime; + *stime = t->stime; + + /* Task is sleeping or idle, nothing to add */ + if (vtime->state < VTIME_SYS) + continue; + + ret = true; + delta = vtime_delta(vtime); + + /* + * Task runs either in user (including guest) or kernel space, + * add pending nohz time to the right place. + */ + if (vtime->state == VTIME_SYS) + *stime += vtime->stime + delta; + else + *utime += vtime->utime + delta; + } while (read_seqcount_retry(&vtime->seqcount, seq)); + + return ret; +} + +static int vtime_state_fetch(struct vtime *vtime, int cpu) +{ + int state = READ_ONCE(vtime->state); + + /* + * We raced against a context switch, fetch the + * kcpustat task again. + */ + if (vtime->cpu != cpu && vtime->cpu != -1) + return -EAGAIN; + + /* + * Two possible things here: + * 1) We are seeing the scheduling out task (prev) or any past one. + * 2) We are seeing the scheduling in task (next) but it hasn't + * passed though vtime_task_switch() yet so the pending + * cputime of the prev task may not be flushed yet. + * + * Case 1) is ok but 2) is not. So wait for a safe VTIME state. + */ + if (state == VTIME_INACTIVE) + return -EAGAIN; + + return state; +} + +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 task_struct *tsk, + enum cpu_usage_stat usage, + int cpu, u64 *val) +{ + struct vtime *vtime = &tsk->vtime; + unsigned int seq; + + do { + int state; + + seq = read_seqcount_begin(&vtime->seqcount); + + state = vtime_state_fetch(vtime, cpu); + if (state < 0) + return state; + + *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 (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 (state == VTIME_GUEST && task_nice(tsk) <= 0) + *val += vtime->gtime + vtime_delta(vtime); + break; + case CPUTIME_GUEST_NICE: + if (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; +} + +u64 kcpustat_field(struct kernel_cpustat *kcpustat, + enum cpu_usage_stat usage, int cpu) +{ + u64 *cpustat = kcpustat->cpustat; + u64 val = cpustat[usage]; + struct rq *rq; + int err; + + if (!vtime_accounting_enabled_cpu(cpu)) + return val; + + rq = cpu_rq(cpu); + + for (;;) { + struct task_struct *curr; + + rcu_read_lock(); + curr = rcu_dereference(rq->curr); + if (WARN_ON_ONCE(!curr)) { + rcu_read_unlock(); + return cpustat[usage]; + } + + err = kcpustat_field_vtime(cpustat, curr, usage, cpu, &val); + rcu_read_unlock(); + + if (!err) + return val; + + cpu_relax(); + } +} +EXPORT_SYMBOL_GPL(kcpustat_field); + +static int kcpustat_cpu_fetch_vtime(struct kernel_cpustat *dst, + const struct kernel_cpustat *src, + struct task_struct *tsk, int cpu) +{ + struct vtime *vtime = &tsk->vtime; + unsigned int seq; + + do { + u64 *cpustat; + u64 delta; + int state; + + seq = read_seqcount_begin(&vtime->seqcount); + + state = vtime_state_fetch(vtime, cpu); + if (state < 0) + return state; + + *dst = *src; + cpustat = dst->cpustat; + + /* Task is sleeping, dead or idle, nothing to add */ + if (state < VTIME_SYS) + continue; + + delta = vtime_delta(vtime); + + /* + * Task runs either in user (including guest) or kernel space, + * add pending nohz time to the right place. + */ + if (state == VTIME_SYS) { + cpustat[CPUTIME_SYSTEM] += vtime->stime + delta; + } else if (state == VTIME_USER) { + if (task_nice(tsk) > 0) + cpustat[CPUTIME_NICE] += vtime->utime + delta; + else + cpustat[CPUTIME_USER] += vtime->utime + delta; + } else { + WARN_ON_ONCE(state != VTIME_GUEST); + if (task_nice(tsk) > 0) { + cpustat[CPUTIME_GUEST_NICE] += vtime->gtime + delta; + cpustat[CPUTIME_NICE] += vtime->gtime + delta; + } else { + cpustat[CPUTIME_GUEST] += vtime->gtime + delta; + cpustat[CPUTIME_USER] += vtime->gtime + delta; + } + } + } while (read_seqcount_retry(&vtime->seqcount, seq)); + + return 0; +} + +void kcpustat_cpu_fetch(struct kernel_cpustat *dst, int cpu) +{ + const struct kernel_cpustat *src = &kcpustat_cpu(cpu); + struct rq *rq; + int err; + + if (!vtime_accounting_enabled_cpu(cpu)) { + *dst = *src; + return; + } + + rq = cpu_rq(cpu); + + for (;;) { + struct task_struct *curr; + + rcu_read_lock(); + curr = rcu_dereference(rq->curr); + if (WARN_ON_ONCE(!curr)) { + rcu_read_unlock(); + *dst = *src; + return; + } + + err = kcpustat_cpu_fetch_vtime(dst, src, curr, cpu); + rcu_read_unlock(); + + if (!err) + return; + + cpu_relax(); + } +} +EXPORT_SYMBOL_GPL(kcpustat_cpu_fetch); + +#endif /* CONFIG_VIRT_CPU_ACCOUNTING_GEN */ |