Re: [RFC] Patch: dynticks: idle load balancing

From: Ingo Molnar
Date: Wed Dec 13 2006 - 17:46:13 EST



* Siddha, Suresh B <suresh.b.siddha@xxxxxxxxx> wrote:

> Appended patch attempts to fix the process idle load balancing in the
> presence of dynticks. cpus for which ticks are stopped will sleep till
> the next event wakes it up. Potentially these sleeps can be for large
> durations and during which today, there is no idle load balancing
> being done. There was some discussion happened(last year) on this
> topic on lkml, where two main approaches were gettting debated. One is
> to back off the idle load balancing for bigger intervals and the
> second is a watchdog mechanism where the busy cpu will trigger the
> load balance on an idle cpu. Both of these mechanisms have its
> drawbacks.

nice work! I have added your patch to -rt. Btw., it needs the patch
below to work on 64-bit.

Ingo

Index: linux/kernel/sched.c
===================================================================
--- linux.orig/kernel/sched.c
+++ linux/kernel/sched.c
@@ -1170,7 +1170,7 @@ static void resched_task(struct task_str
static void resched_cpu(int cpu)
{
struct rq *rq = cpu_rq(cpu);
- unsigned int flags;
+ unsigned long flags;

spin_lock_irqsave(&rq->lock, flags);
resched_task(cpu_curr(cpu));
-
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