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sched, nohz: Introduce nohz_flags in 'struct rq'

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Introduce nohz_flags in the struct rq, which will track these two flags
for now.

NOHZ_TICK_STOPPED keeps track of the tick stopped status that gets set when
the tick is stopped. It will be used to update the nohz idle load balancer data
structures during the first busy tick after the tick is restarted. At this
first busy tick after tickless idle, NOHZ_TICK_STOPPED flag will be reset.
This will minimize the nohz idle load balancer status updates that currently
happen for every tickless exit, making it more scalable when there
are many logical cpu's that enter and exit idle often.

NOHZ_BALANCE_KICK will track the need for nohz idle load balance
on this rq. This will replace the nohz_balance_kick in the rq, which was
not being updated atomically.

Signed-off-by: Suresh Siddha <suresh.b.siddha@intel.com>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: http://lkml.kernel.org/r/20111202010832.499438999@sbsiddha-desk.sc.intel.com
Signed-off-by: Ingo Molnar <mingo@elte.hu>
This commit is contained in:
Suresh Siddha
2011-12-01 17:07:32 -08:00
committed by Ingo Molnar
parent 5b680fd613
commit 1c792db7f7
3 changed files with 40 additions and 24 deletions
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5
kernel/sched/core.c
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@@ -575,7 +575,8 @@ void wake_up_idle_cpu(int cpu)
static inline bool got_nohz_idle_kick(void)
{
return idle_cpu(smp_processor_id()) && this_rq()->nohz_balance_kick;
int cpu = smp_processor_id();
return idle_cpu(cpu) && test_bit(NOHZ_BALANCE_KICK, nohz_flags(cpu));
}
#else /* CONFIG_NO_HZ */
@@ -6840,7 +6841,7 @@ void __init sched_init(void)
rq->avg_idle = 2*sysctl_sched_migration_cost;
rq_attach_root(rq, &def_root_domain);
#ifdef CONFIG_NO_HZ
rq->nohz_balance_kick = 0;
rq->nohz_flags = 0;
#endif
#endif
init_rq_hrtick(rq);