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Commit aa483808 authored by Venkatesh Pallipadi's avatar Venkatesh Pallipadi Committed by Ingo Molnar
Browse files

sched: Remove irq time from available CPU power 

The idea was suggested by Peter Zijlstra here:

  http://marc.info/?l=linux-kernel&m=127476934517534&w=2



irq time is technically not available to the tasks running on the CPU.
This patch removes irq time from CPU power piggybacking on
sched_rt_avg_update().

Tested this by keeping CPU X busy with a network intensive task having 75%
oa a single CPU irq processing (hard+soft) on a 4-way system. And start seven
cycle soakers on the system. Without this change, there will be two tasks on
each CPU. With this change, there is a single task on irq busy CPU X and
remaining 7 tasks are spread around among other 3 CPUs.

Signed-off-by: default avatarVenkatesh Pallipadi <venki@google.com>
Signed-off-by: default avatarPeter Zijlstra <a.p.zijlstra@chello.nl>
LKML-Reference: <1286237003-12406-8-git-send-email-venki@google.com>
Signed-off-by: default avatarIngo Molnar <mingo@elte.hu>
parent 305e6835

kernel/sched.c

+18 −0
Original line number Original line Diff line number Diff line
@@ -519,6 +519,10 @@ struct rq { 
	u64 avg_idle;

	u64 avg_idle;

#endif

#endif





#ifdef CONFIG_IRQ_TIME_ACCOUNTING

	u64 prev_irq_time;

#endif



	/* calc_load related fields */

	/* calc_load related fields */

	unsigned long calc_load_update;

	unsigned long calc_load_update;

	long calc_load_active;

	long calc_load_active;
@@ -643,6 +647,7 @@ static inline struct task_group *task_group(struct task_struct *p) 
#endif /* CONFIG_CGROUP_SCHED */

#endif /* CONFIG_CGROUP_SCHED */





static u64 irq_time_cpu(int cpu);

static u64 irq_time_cpu(int cpu);

static void sched_irq_time_avg_update(struct rq *rq, u64 irq_time);





inline void update_rq_clock(struct rq *rq)

inline void update_rq_clock(struct rq *rq)

{

{
@@ -654,6 +659,8 @@ inline void update_rq_clock(struct rq *rq) 
		irq_time = irq_time_cpu(cpu);

		irq_time = irq_time_cpu(cpu);

		if (rq->clock - irq_time > rq->clock_task)

		if (rq->clock - irq_time > rq->clock_task)

			rq->clock_task = rq->clock - irq_time;

			rq->clock_task = rq->clock - irq_time;



		sched_irq_time_avg_update(rq, irq_time);

	}

	}

}

}
@@ -1985,6 +1992,15 @@ void account_system_vtime(struct task_struct *curr) 
	local_irq_restore(flags);

	local_irq_restore(flags);

}

}





static void sched_irq_time_avg_update(struct rq *rq, u64 curr_irq_time)

{

	if (sched_clock_irqtime && sched_feat(NONIRQ_POWER)) {

		u64 delta_irq = curr_irq_time - rq->prev_irq_time;

		rq->prev_irq_time = curr_irq_time;

		sched_rt_avg_update(rq, delta_irq);

	}

}



#else

#else





static u64 irq_time_cpu(int cpu)

static u64 irq_time_cpu(int cpu)
@@ -1992,6 +2008,8 @@ static u64 irq_time_cpu(int cpu) 
	return 0;

	return 0;

}

}





static void sched_irq_time_avg_update(struct rq *rq, u64 curr_irq_time) { }



#endif

#endif





#include "sched_idletask.c"

#include "sched_idletask.c"

kernel/sched_fair.c

+7 −1
Original line number Original line Diff line number Diff line
@@ -2275,7 +2275,13 @@ unsigned long scale_rt_power(int cpu) 
	u64 total, available;

	u64 total, available;





	total = sched_avg_period() + (rq->clock - rq->age_stamp);

	total = sched_avg_period() + (rq->clock - rq->age_stamp);



	if (unlikely(total < rq->rt_avg)) {

		/* Ensures that power won't end up being negative */

		available = 0;

	} else {

		available = total - rq->rt_avg;

		available = total - rq->rt_avg;

	}





	if (unlikely((s64)total < SCHED_LOAD_SCALE))

	if (unlikely((s64)total < SCHED_LOAD_SCALE))

		total = SCHED_LOAD_SCALE;

		total = SCHED_LOAD_SCALE;

kernel/sched_features.h

+5 −0
Original line number Original line Diff line number Diff line
@@ -61,3 +61,8 @@ SCHED_FEAT(ASYM_EFF_LOAD, 1) 
 * release the lock. Decreases scheduling overhead.

 * release the lock. Decreases scheduling overhead.

 */

 */

SCHED_FEAT(OWNER_SPIN, 1)

SCHED_FEAT(OWNER_SPIN, 1)



/*

 * Decrement CPU power based on irq activity

 */

SCHED_FEAT(NONIRQ_POWER, 1)