This is a note to let you know that I've just added the patch titled
sched: Remove irq time from available CPU power
to the 2.6.32-longterm tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/longterm/longterm-queue-2.6.32.git;a=summary
The filename of the patch is:
0020-sched-Remove-irq-time-from-available-CPU-power.patch
and it can be found in the queue-2.6.32 subdirectory.
If you, or anyone else, feels it should not be added to the 2.6.32 longterm
tree,
please let <[email protected]> know about it.
>From 7c2accd958cf88e35753cd3ac87eca28dfd101fa Mon Sep 17 00:00:00 2001
From: Venkatesh Pallipadi <[email protected]>
Date: Thu, 10 Feb 2011 10:23:27 +0100
Subject: sched: Remove irq time from available CPU power
Commit: aa483808516ca5cacfa0e5849691f64fec25828e upstream
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]>
Signed-off-by: Greg Kroah-Hartman <[email protected]>
---
kernel/sched.c | 26 +++++++++++++++++++++++++-
kernel/sched_features.h | 5 +++++
2 files changed, 30 insertions(+), 1 deletion(-)
--- a/kernel/sched.c
+++ b/kernel/sched.c
@@ -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 *r
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_st
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;
--- a/kernel/sched_features.h
+++ b/kernel/sched_features.h
@@ -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)
Patches currently in longterm-queue-2.6.32 which might be from [email protected]
are
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