The patch titled
sched: fix idle load balancing in softirqd context
has been added to the -mm tree. Its filename is
sched-fix-idle-load-balancing-in-softirqd-context.patch
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See http://www.zip.com.au/~akpm/linux/patches/stuff/added-to-mm.txt to find
out what to do about this
------------------------------------------------------
Subject: sched: fix idle load balancing in softirqd context
From: "Siddha, Suresh B" <suresh.b.siddha@xxxxxxxxx>
Periodic load balancing in recent kernels happen in the softirq. In
certain -rt configurations, these softirqs are handled in softirqd context.
And hence the check for idle processor was always returning busy (as
nr_running > 1).
This patch captures the idle information at the tick and passes this info
to softirq context through an element 'idle_at_tick' in rq.
Signed-off-by: Suresh Siddha <suresh.b.siddha@xxxxxxxxx>
Cc: Ingo Molnar <mingo@xxxxxxx>
Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Cc: Nick Piggin <nickpiggin@xxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
kernel/sched.c | 12 +++++-------
1 files changed, 5 insertions(+), 7 deletions(-)
diff -puN kernel/sched.c~sched-fix-idle-load-balancing-in-softirqd-context kernel/sched.c
--- a/kernel/sched.c~sched-fix-idle-load-balancing-in-softirqd-context
+++ a/kernel/sched.c
@@ -223,6 +223,7 @@ struct rq {
unsigned long raw_weighted_load;
#ifdef CONFIG_SMP
unsigned long cpu_load[3];
+ unsigned char idle_at_tick;
#endif
unsigned long long nr_switches;
@@ -2944,12 +2945,7 @@ static void run_rebalance_domains(struct
struct rq *this_rq = cpu_rq(this_cpu);
unsigned long interval;
struct sched_domain *sd;
- /*
- * We are idle if there are no processes running. This
- * is valid even if we are the idle process (SMT).
- */
- enum idle_type idle = !this_rq->nr_running ?
- SCHED_IDLE : NOT_IDLE;
+ enum idle_type idle = this_rq->idle_at_tick ? SCHED_IDLE : NOT_IDLE;
/* Earliest time when we have to call run_rebalance_domains again */
unsigned long next_balance = jiffies + 60*HZ;
@@ -3236,17 +3232,19 @@ void scheduler_tick(void)
unsigned long long now = sched_clock();
struct task_struct *p = current;
int cpu = smp_processor_id();
+ int idle_at_tick = idle_cpu(cpu);
struct rq *rq = cpu_rq(cpu);
update_cpu_clock(p, rq, now);
- if (p == rq->idle)
+ if (idle_at_tick)
/* Task on the idle queue */
wake_priority_sleeper(rq);
else
task_running_tick(rq, p);
#ifdef CONFIG_SMP
update_load(rq);
+ rq->idle_at_tick = idle_at_tick;
if (time_after_eq(jiffies, rq->next_balance))
raise_softirq(SCHED_SOFTIRQ);
#endif
_
Patches currently in -mm which might be from suresh.b.siddha@xxxxxxxxx are
sched-fix-idle-load-balancing-in-softirqd-context.patch
sched-dynticks-idle-load-balancing-v2.patch
mm-only-sched-add-a-few-scheduler-event-counters.patch
-
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