Merge branch 'sched-fixes-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/linux-2.6-tip
* 'sched-fixes-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/linux-2.6-tip: sched: Fix the irqtime code for 32bit sched: Fix the irqtime code to deal with u64 wraps nohz: Fix get_next_timer_interrupt() vs cpu hotplug Sched: fix skip_clock_update optimization sched: Cure more NO_HZ load average woes
This commit is contained in:
Linus Torvalds
Коммит
21228e4557
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@ -143,7 +143,7 @@ extern unsigned long nr_iowait_cpu(int cpu);
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extern unsigned long this_cpu_load(void);
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extern void calc_global_load(void);
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extern void calc_global_load(unsigned long ticks);
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extern unsigned long get_parent_ip(unsigned long addr);
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@ -273,6 +273,7 @@ static struct task_struct *dup_task_struct(struct task_struct *orig)
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setup_thread_stack(tsk, orig);
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clear_user_return_notifier(tsk);
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clear_tsk_need_resched(tsk);
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stackend = end_of_stack(tsk);
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*stackend = STACK_END_MAGIC; /* for overflow detection */
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292
kernel/sched.c
292
kernel/sched.c
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@ -636,22 +636,18 @@ static inline struct task_group *task_group(struct task_struct *p)
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#endif /* CONFIG_CGROUP_SCHED */
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static u64 irq_time_cpu(int cpu);
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static void sched_irq_time_avg_update(struct rq *rq, u64 irq_time);
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static void update_rq_clock_task(struct rq *rq, s64 delta);
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inline void update_rq_clock(struct rq *rq)
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static void update_rq_clock(struct rq *rq)
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{
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if (!rq->skip_clock_update) {
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int cpu = cpu_of(rq);
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u64 irq_time;
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s64 delta;
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rq->clock = sched_clock_cpu(cpu);
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irq_time = irq_time_cpu(cpu);
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if (rq->clock - irq_time > rq->clock_task)
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rq->clock_task = rq->clock - irq_time;
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if (rq->skip_clock_update)
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return;
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sched_irq_time_avg_update(rq, irq_time);
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}
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delta = sched_clock_cpu(cpu_of(rq)) - rq->clock;
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rq->clock += delta;
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update_rq_clock_task(rq, delta);
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}
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/*
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@ -1924,10 +1920,9 @@ static void deactivate_task(struct rq *rq, struct task_struct *p, int flags)
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* They are read and saved off onto struct rq in update_rq_clock().
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* This may result in other CPU reading this CPU's irq time and can
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* race with irq/account_system_vtime on this CPU. We would either get old
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* or new value (or semi updated value on 32 bit) with a side effect of
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* accounting a slice of irq time to wrong task when irq is in progress
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* while we read rq->clock. That is a worthy compromise in place of having
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* locks on each irq in account_system_time.
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* or new value with a side effect of accounting a slice of irq time to wrong
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* task when irq is in progress while we read rq->clock. That is a worthy
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* compromise in place of having locks on each irq in account_system_time.
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*/
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static DEFINE_PER_CPU(u64, cpu_hardirq_time);
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static DEFINE_PER_CPU(u64, cpu_softirq_time);
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@ -1945,19 +1940,58 @@ void disable_sched_clock_irqtime(void)
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sched_clock_irqtime = 0;
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}
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static u64 irq_time_cpu(int cpu)
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{
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if (!sched_clock_irqtime)
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return 0;
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#ifndef CONFIG_64BIT
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static DEFINE_PER_CPU(seqcount_t, irq_time_seq);
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return per_cpu(cpu_softirq_time, cpu) + per_cpu(cpu_hardirq_time, cpu);
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static inline void irq_time_write_begin(void)
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{
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__this_cpu_inc(irq_time_seq.sequence);
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smp_wmb();
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}
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static inline void irq_time_write_end(void)
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{
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smp_wmb();
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__this_cpu_inc(irq_time_seq.sequence);
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}
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static inline u64 irq_time_read(int cpu)
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{
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u64 irq_time;
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unsigned seq;
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do {
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seq = read_seqcount_begin(&per_cpu(irq_time_seq, cpu));
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irq_time = per_cpu(cpu_softirq_time, cpu) +
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per_cpu(cpu_hardirq_time, cpu);
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} while (read_seqcount_retry(&per_cpu(irq_time_seq, cpu), seq));
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return irq_time;
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}
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#else /* CONFIG_64BIT */
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static inline void irq_time_write_begin(void)
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{
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}
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static inline void irq_time_write_end(void)
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{
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}
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static inline u64 irq_time_read(int cpu)
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{
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return per_cpu(cpu_softirq_time, cpu) + per_cpu(cpu_hardirq_time, cpu);
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}
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#endif /* CONFIG_64BIT */
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/*
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* Called before incrementing preempt_count on {soft,}irq_enter
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* and before decrementing preempt_count on {soft,}irq_exit.
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*/
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void account_system_vtime(struct task_struct *curr)
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{
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unsigned long flags;
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s64 delta;
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int cpu;
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u64 now, delta;
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if (!sched_clock_irqtime)
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return;
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@ -1965,9 +1999,10 @@ void account_system_vtime(struct task_struct *curr)
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local_irq_save(flags);
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cpu = smp_processor_id();
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now = sched_clock_cpu(cpu);
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delta = now - per_cpu(irq_start_time, cpu);
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per_cpu(irq_start_time, cpu) = now;
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delta = sched_clock_cpu(cpu) - __this_cpu_read(irq_start_time);
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__this_cpu_add(irq_start_time, delta);
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irq_time_write_begin();
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/*
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* We do not account for softirq time from ksoftirqd here.
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* We want to continue accounting softirq time to ksoftirqd thread
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@ -1975,33 +2010,55 @@ void account_system_vtime(struct task_struct *curr)
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* that do not consume any time, but still wants to run.
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*/
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if (hardirq_count())
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per_cpu(cpu_hardirq_time, cpu) += delta;
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__this_cpu_add(cpu_hardirq_time, delta);
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else if (in_serving_softirq() && !(curr->flags & PF_KSOFTIRQD))
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per_cpu(cpu_softirq_time, cpu) += delta;
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__this_cpu_add(cpu_softirq_time, delta);
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irq_time_write_end();
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local_irq_restore(flags);
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}
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EXPORT_SYMBOL_GPL(account_system_vtime);
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static void sched_irq_time_avg_update(struct rq *rq, u64 curr_irq_time)
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static void update_rq_clock_task(struct rq *rq, s64 delta)
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{
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if (sched_clock_irqtime && sched_feat(NONIRQ_POWER)) {
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u64 delta_irq = curr_irq_time - rq->prev_irq_time;
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rq->prev_irq_time = curr_irq_time;
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sched_rt_avg_update(rq, delta_irq);
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}
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s64 irq_delta;
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irq_delta = irq_time_read(cpu_of(rq)) - rq->prev_irq_time;
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/*
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* Since irq_time is only updated on {soft,}irq_exit, we might run into
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* this case when a previous update_rq_clock() happened inside a
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* {soft,}irq region.
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*
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* When this happens, we stop ->clock_task and only update the
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* prev_irq_time stamp to account for the part that fit, so that a next
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* update will consume the rest. This ensures ->clock_task is
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* monotonic.
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*
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* It does however cause some slight miss-attribution of {soft,}irq
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* time, a more accurate solution would be to update the irq_time using
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* the current rq->clock timestamp, except that would require using
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* atomic ops.
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*/
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if (irq_delta > delta)
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irq_delta = delta;
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rq->prev_irq_time += irq_delta;
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delta -= irq_delta;
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rq->clock_task += delta;
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if (irq_delta && sched_feat(NONIRQ_POWER))
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sched_rt_avg_update(rq, irq_delta);
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}
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#else
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#else /* CONFIG_IRQ_TIME_ACCOUNTING */
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static u64 irq_time_cpu(int cpu)
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static void update_rq_clock_task(struct rq *rq, s64 delta)
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{
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return 0;
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rq->clock_task += delta;
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}
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static void sched_irq_time_avg_update(struct rq *rq, u64 curr_irq_time) { }
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#endif
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#endif /* CONFIG_IRQ_TIME_ACCOUNTING */
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#include "sched_idletask.c"
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#include "sched_fair.c"
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@ -2129,7 +2186,7 @@ static void check_preempt_curr(struct rq *rq, struct task_struct *p, int flags)
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* A queue event has occurred, and we're going to schedule. In
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* this case, we can save a useless back to back clock update.
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*/
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if (test_tsk_need_resched(rq->curr))
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if (rq->curr->se.on_rq && test_tsk_need_resched(rq->curr))
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rq->skip_clock_update = 1;
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}
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@ -3119,6 +3176,15 @@ static long calc_load_fold_active(struct rq *this_rq)
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return delta;
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}
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static unsigned long
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calc_load(unsigned long load, unsigned long exp, unsigned long active)
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{
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load *= exp;
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load += active * (FIXED_1 - exp);
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load += 1UL << (FSHIFT - 1);
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return load >> FSHIFT;
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}
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#ifdef CONFIG_NO_HZ
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/*
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* For NO_HZ we delay the active fold to the next LOAD_FREQ update.
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@ -3148,6 +3214,128 @@ static long calc_load_fold_idle(void)
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return delta;
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}
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/**
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* fixed_power_int - compute: x^n, in O(log n) time
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*
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* @x: base of the power
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* @frac_bits: fractional bits of @x
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* @n: power to raise @x to.
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*
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* By exploiting the relation between the definition of the natural power
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* function: x^n := x*x*...*x (x multiplied by itself for n times), and
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* the binary encoding of numbers used by computers: n := \Sum n_i * 2^i,
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* (where: n_i \elem {0, 1}, the binary vector representing n),
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* we find: x^n := x^(\Sum n_i * 2^i) := \Prod x^(n_i * 2^i), which is
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* of course trivially computable in O(log_2 n), the length of our binary
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* vector.
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*/
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static unsigned long
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fixed_power_int(unsigned long x, unsigned int frac_bits, unsigned int n)
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{
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unsigned long result = 1UL << frac_bits;
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if (n) for (;;) {
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if (n & 1) {
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result *= x;
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result += 1UL << (frac_bits - 1);
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result >>= frac_bits;
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}
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n >>= 1;
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if (!n)
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break;
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x *= x;
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x += 1UL << (frac_bits - 1);
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x >>= frac_bits;
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}
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return result;
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}
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/*
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* a1 = a0 * e + a * (1 - e)
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*
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* a2 = a1 * e + a * (1 - e)
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* = (a0 * e + a * (1 - e)) * e + a * (1 - e)
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* = a0 * e^2 + a * (1 - e) * (1 + e)
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*
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* a3 = a2 * e + a * (1 - e)
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* = (a0 * e^2 + a * (1 - e) * (1 + e)) * e + a * (1 - e)
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* = a0 * e^3 + a * (1 - e) * (1 + e + e^2)
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*
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* ...
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*
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* an = a0 * e^n + a * (1 - e) * (1 + e + ... + e^n-1) [1]
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* = a0 * e^n + a * (1 - e) * (1 - e^n)/(1 - e)
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* = a0 * e^n + a * (1 - e^n)
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*
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* [1] application of the geometric series:
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*
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* n 1 - x^(n+1)
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* S_n := \Sum x^i = -------------
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* i=0 1 - x
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*/
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static unsigned long
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calc_load_n(unsigned long load, unsigned long exp,
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unsigned long active, unsigned int n)
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{
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return calc_load(load, fixed_power_int(exp, FSHIFT, n), active);
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}
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/*
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* NO_HZ can leave us missing all per-cpu ticks calling
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* calc_load_account_active(), but since an idle CPU folds its delta into
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* calc_load_tasks_idle per calc_load_account_idle(), all we need to do is fold
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* in the pending idle delta if our idle period crossed a load cycle boundary.
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*
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* Once we've updated the global active value, we need to apply the exponential
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* weights adjusted to the number of cycles missed.
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*/
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static void calc_global_nohz(unsigned long ticks)
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{
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long delta, active, n;
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if (time_before(jiffies, calc_load_update))
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return;
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|
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/*
|
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* If we crossed a calc_load_update boundary, make sure to fold
|
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* any pending idle changes, the respective CPUs might have
|
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* missed the tick driven calc_load_account_active() update
|
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* due to NO_HZ.
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*/
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delta = calc_load_fold_idle();
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if (delta)
|
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atomic_long_add(delta, &calc_load_tasks);
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|
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/*
|
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* If we were idle for multiple load cycles, apply them.
|
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*/
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if (ticks >= LOAD_FREQ) {
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n = ticks / LOAD_FREQ;
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|
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active = atomic_long_read(&calc_load_tasks);
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active = active > 0 ? active * FIXED_1 : 0;
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avenrun[0] = calc_load_n(avenrun[0], EXP_1, active, n);
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avenrun[1] = calc_load_n(avenrun[1], EXP_5, active, n);
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avenrun[2] = calc_load_n(avenrun[2], EXP_15, active, n);
|
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|
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calc_load_update += n * LOAD_FREQ;
|
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}
|
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|
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/*
|
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* Its possible the remainder of the above division also crosses
|
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* a LOAD_FREQ period, the regular check in calc_global_load()
|
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* which comes after this will take care of that.
|
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*
|
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* Consider us being 11 ticks before a cycle completion, and us
|
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* sleeping for 4*LOAD_FREQ + 22 ticks, then the above code will
|
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* age us 4 cycles, and the test in calc_global_load() will
|
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* pick up the final one.
|
||||
*/
|
||||
}
|
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#else
|
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static void calc_load_account_idle(struct rq *this_rq)
|
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{
|
||||
|
|
@ -3157,6 +3345,10 @@ static inline long calc_load_fold_idle(void)
|
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{
|
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return 0;
|
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}
|
||||
|
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static void calc_global_nohz(unsigned long ticks)
|
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{
|
||||
}
|
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#endif
|
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|
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/**
|
||||
|
|
@ -3174,24 +3366,17 @@ void get_avenrun(unsigned long *loads, unsigned long offset, int shift)
|
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loads[2] = (avenrun[2] + offset) << shift;
|
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}
|
||||
|
||||
static unsigned long
|
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calc_load(unsigned long load, unsigned long exp, unsigned long active)
|
||||
{
|
||||
load *= exp;
|
||||
load += active * (FIXED_1 - exp);
|
||||
return load >> FSHIFT;
|
||||
}
|
||||
|
||||
/*
|
||||
* calc_load - update the avenrun load estimates 10 ticks after the
|
||||
* CPUs have updated calc_load_tasks.
|
||||
*/
|
||||
void calc_global_load(void)
|
||||
void calc_global_load(unsigned long ticks)
|
||||
{
|
||||
unsigned long upd = calc_load_update + 10;
|
||||
long active;
|
||||
|
||||
if (time_before(jiffies, upd))
|
||||
calc_global_nohz(ticks);
|
||||
|
||||
if (time_before(jiffies, calc_load_update + 10))
|
||||
return;
|
||||
|
||||
active = atomic_long_read(&calc_load_tasks);
|
||||
|
|
@ -3845,7 +4030,6 @@ static void put_prev_task(struct rq *rq, struct task_struct *prev)
|
|||
{
|
||||
if (prev->se.on_rq)
|
||||
update_rq_clock(rq);
|
||||
rq->skip_clock_update = 0;
|
||||
prev->sched_class->put_prev_task(rq, prev);
|
||||
}
|
||||
|
||||
|
|
@ -3903,7 +4087,6 @@ need_resched_nonpreemptible:
|
|||
hrtick_clear(rq);
|
||||
|
||||
raw_spin_lock_irq(&rq->lock);
|
||||
clear_tsk_need_resched(prev);
|
||||
|
||||
switch_count = &prev->nivcsw;
|
||||
if (prev->state && !(preempt_count() & PREEMPT_ACTIVE)) {
|
||||
|
|
@ -3935,6 +4118,8 @@ need_resched_nonpreemptible:
|
|||
|
||||
put_prev_task(rq, prev);
|
||||
next = pick_next_task(rq);
|
||||
clear_tsk_need_resched(prev);
|
||||
rq->skip_clock_update = 0;
|
||||
|
||||
if (likely(prev != next)) {
|
||||
sched_info_switch(prev, next);
|
||||
|
|
@ -3943,6 +4128,7 @@ need_resched_nonpreemptible:
|
|||
rq->nr_switches++;
|
||||
rq->curr = next;
|
||||
++*switch_count;
|
||||
WARN_ON_ONCE(test_tsk_need_resched(next));
|
||||
|
||||
context_switch(rq, prev, next); /* unlocks the rq */
|
||||
/*
|
||||
|
|
|
|||
|
|
@ -1252,6 +1252,12 @@ unsigned long get_next_timer_interrupt(unsigned long now)
|
|||
struct tvec_base *base = __get_cpu_var(tvec_bases);
|
||||
unsigned long expires;
|
||||
|
||||
/*
|
||||
* Pretend that there is no timer pending if the cpu is offline.
|
||||
* Possible pending timers will be migrated later to an active cpu.
|
||||
*/
|
||||
if (cpu_is_offline(smp_processor_id()))
|
||||
return now + NEXT_TIMER_MAX_DELTA;
|
||||
spin_lock(&base->lock);
|
||||
if (time_before_eq(base->next_timer, base->timer_jiffies))
|
||||
base->next_timer = __next_timer_interrupt(base);
|
||||
|
|
@ -1319,7 +1325,7 @@ void do_timer(unsigned long ticks)
|
|||
{
|
||||
jiffies_64 += ticks;
|
||||
update_wall_time();
|
||||
calc_global_load();
|
||||
calc_global_load(ticks);
|
||||
}
|
||||
|
||||
#ifdef __ARCH_WANT_SYS_ALARM
|
||||
|
|
|
|||
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