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sched: Remove irq time from available CPU power

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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: Venkatesh Pallipadi <venki@google.com>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
LKML-Reference: <1286237003-12406-8-git-send-email-venki@google.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
This commit is contained in:
Venkatesh Pallipadi 2010-10-04 17:03:22 -07:00 committed by Ingo Molnar
parent 305e6835e0
commit aa48380851
3 changed files with 30 additions and 1 deletions
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18
kernel/sched.c
View file

@ -519,6 +519,10 @@ struct rq {
u64 avg_idle;
#endif
#ifdef CONFIG_IRQ_TIME_ACCOUNTING
u64 prev_irq_time;
#endif
/* calc_load related fields */
unsigned long calc_load_update;
long calc_load_active;
@ -643,6 +647,7 @@ static inline struct task_group *task_group(struct task_struct *p)
#endif /* CONFIG_CGROUP_SCHED */
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)
{
@ -654,6 +659,8 @@ inline void update_rq_clock(struct rq *rq)
irq_time = irq_time_cpu(cpu);
if (rq->clock - irq_time > rq->clock_task)
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);
}
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
static u64 irq_time_cpu(int cpu)
@ -1992,6 +2008,8 @@ static u64 irq_time_cpu(int cpu)
return 0;
}
static void sched_irq_time_avg_update(struct rq *rq, u64 curr_irq_time) { }
#endif
#include "sched_idletask.c"

8
kernel/sched_fair.c
View file

@ -2275,7 +2275,13 @@ unsigned long scale_rt_power(int cpu)
u64 total, available;
total = sched_avg_period() + (rq->clock - rq->age_stamp);
available = total - rq->rt_avg;
if (unlikely(total < rq->rt_avg)) {
/* Ensures that power won't end up being negative */
available = 0;
} else {
available = total - rq->rt_avg;
}
if (unlikely((s64)total < SCHED_LOAD_SCALE))
total = SCHED_LOAD_SCALE;

5
kernel/sched_features.h
View file

@ -61,3 +61,8 @@ SCHED_FEAT(ASYM_EFF_LOAD, 1)
* release the lock. Decreases scheduling overhead.
*/
SCHED_FEAT(OWNER_SPIN, 1)
/*
* Decrement CPU power based on irq activity
*/
SCHED_FEAT(NONIRQ_POWER, 1)