Skip to contentSkip to conversation

sched: Remove irq time from available CPU power

PATCH New stable-bot for Venkatesh Pallipadi 1 participant 1 message Feb 10, 2011

lore
Share & tools
lore

stable-bot for Venkatesh Pallipadi

author
#0 lore raw

PATCH 20/28 sched: Remove irq time from available CPU power

Commit: aa483808516ca5cacfa0e5849691f64fec25828e upstream
Author: Venkatesh Pallipadi <[email protected]>
AuthorDate: Mon Oct 4 17:03:22 2010 -0700

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 <[email protected]>
Signed-off-by Peter Zijlstra <[email protected]>

LKML-Reference: <[email protected]>

Signed-off-by Ingo Molnar <[email protected]>
Signed-off-by Mike Galbraith <[email protected]>
Acked-by Peter Zijlstra <[email protected]>
---
 kernel/sched.c          |   26 +++++++++++++++++++++++++-
 kernel/sched_features.h |    5 +++++
 2 files changed, 30 insertions(+), 1 deletions(-)
kernel/sched.c +25 -1
index 5761f09..4f86094 100644
@@ -553,6 +553,10 @@ 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;

@@ -622,6 +626,7 @@ static inline int cpu_of(struct rq *rq)
 #define raw_rq()		(&__raw_get_cpu_var(runqueues))
 
 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)
 {

@@ -632,6 +637,8 @@ 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);
 }
 
 /*

@@ -1883,6 +1890,15 @@ 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)

@@ -1890,6 +1906,8 @@ 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_stats.h"

@@ -3755,7 +3773,13 @@ 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;
kernel/sched_features.h +5 -0
index 0d94083..f8df3ee 100644
@@ -121,3 +121,8 @@ 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)
Signature · 1 line
1.7.4