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authorSiddha, Suresh B <suresh.b.siddha@intel.com>2007-05-08 00:32:48 -0700
committerLinus Torvalds <torvalds@woody.linux-foundation.org>2007-05-08 11:15:17 -0700
commitbdecea3a9282d529b54954f3f1e59877629baba1 (patch)
treec7330b1cec4b4a9bf18657bc99100276343efc38 /kernel/sched.c
parent2bd7e20e0d24325b0799544bc8105cc57cc8e2aa (diff)
downloadop-kernel-dev-bdecea3a9282d529b54954f3f1e59877629baba1.zip
op-kernel-dev-bdecea3a9282d529b54954f3f1e59877629baba1.tar.gz
sched: fix idle load balancing in softirqd context
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. [kernel@kolivas.org: Fix reverse idle at tick logic] Signed-off-by: Suresh Siddha <suresh.b.siddha@intel.com> Acked-by: Ingo Molnar <mingo@elte.hu> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: Nick Piggin <nickpiggin@yahoo.com.au> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'kernel/sched.c')
-rw-r--r--kernel/sched.c12
1 files changed, 5 insertions, 7 deletions
diff --git a/kernel/sched.c b/kernel/sched.c
index 5530ed2..ba053d8 100644
--- a/kernel/sched.c
+++ b/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;
@@ -2943,12 +2944,7 @@ static void run_rebalance_domains(struct softirq_action *h)
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;
@@ -3218,14 +3214,16 @@ 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_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
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