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Commit 0bcdcf28 authored by Christian Ehrhardt's avatar Christian Ehrhardt Committed by Ingo Molnar
Browse files

sched: Fix missing sched tunable recalculation on cpu add/remove 



Based on Peter Zijlstras patch suggestion this enables recalculation of
the scheduler tunables in response of a change in the number of cpus. It
also adds a max of eight cpus that are considered in that scaling.

Signed-off-by: default avatarChristian Ehrhardt <ehrhardt@linux.vnet.ibm.com>
Signed-off-by: default avatarPeter Zijlstra <a.p.zijlstra@chello.nl>
LKML-Reference: <1259579808-11357-2-git-send-email-ehrhardt@linux.vnet.ibm.com>
Signed-off-by: default avatarIngo Molnar <mingo@elte.hu>
parent 57785df5

kernel/sched.c

+16 −13
Original line number Diff line number Diff line
@@ -814,6 +814,7 @@ const_debug unsigned int sysctl_sched_nr_migrate = 32; 
 * default: 0.25ms

 */

unsigned int sysctl_sched_shares_ratelimit = 250000;

unsigned int normalized_sysctl_sched_shares_ratelimit = 250000;



/*

 * Inject some fuzzyness into changing the per-cpu group shares
@@ -1814,6 +1815,7 @@ static void cfs_rq_set_shares(struct cfs_rq *cfs_rq, unsigned long shares) 
#endif



static void calc_load_account_active(struct rq *this_rq);

static void update_sysctl(void);



static inline void __set_task_cpu(struct task_struct *p, unsigned int cpu)

{
@@ -7028,22 +7030,23 @@ cpumask_var_t nohz_cpu_mask; 
 *

 * This idea comes from the SD scheduler of Con Kolivas:

 */

static inline void sched_init_granularity(void)

static void update_sysctl(void)

{

	unsigned int factor = 1 + ilog2(num_online_cpus());

	const unsigned long limit = 200000000;



	sysctl_sched_min_granularity *= factor;

	if (sysctl_sched_min_granularity > limit)

		sysctl_sched_min_granularity = limit;



	sysctl_sched_latency *= factor;

	if (sysctl_sched_latency > limit)

		sysctl_sched_latency = limit;

	unsigned int cpus = min(num_online_cpus(), 8U);

	unsigned int factor = 1 + ilog2(cpus);



	sysctl_sched_wakeup_granularity *= factor;

#define SET_SYSCTL(name) \

	(sysctl_##name = (factor) * normalized_sysctl_##name)

	SET_SYSCTL(sched_min_granularity);

	SET_SYSCTL(sched_latency);

	SET_SYSCTL(sched_wakeup_granularity);

	SET_SYSCTL(sched_shares_ratelimit);

#undef SET_SYSCTL

}



	sysctl_sched_shares_ratelimit *= factor;

static inline void sched_init_granularity(void)

{

	update_sysctl();

}



#ifdef CONFIG_SMP

kernel/sched_fair.c

+16 −0
Original line number Diff line number Diff line
@@ -35,12 +35,14 @@ 
 *  run vmstat and monitor the context-switches (cs) field)

 */

unsigned int sysctl_sched_latency = 5000000ULL;

unsigned int normalized_sysctl_sched_latency = 5000000ULL;



/*

 * Minimal preemption granularity for CPU-bound tasks:

 * (default: 1 msec * (1 + ilog(ncpus)), units: nanoseconds)

 */

unsigned int sysctl_sched_min_granularity = 1000000ULL;

unsigned int normalized_sysctl_sched_min_granularity = 1000000ULL;



/*

 * is kept at sysctl_sched_latency / sysctl_sched_min_granularity
@@ -70,6 +72,7 @@ unsigned int __read_mostly sysctl_sched_compat_yield; 
 * have immediate wakeup/sleep latencies.

 */

unsigned int sysctl_sched_wakeup_granularity = 1000000UL;

unsigned int normalized_sysctl_sched_wakeup_granularity = 1000000UL;



const_debug unsigned int sysctl_sched_migration_cost = 500000UL;
@@ -1890,6 +1893,17 @@ move_one_task_fair(struct rq *this_rq, int this_cpu, struct rq *busiest, 


	return 0;

}



static void rq_online_fair(struct rq *rq)

{

	update_sysctl();

}



static void rq_offline_fair(struct rq *rq)

{

	update_sysctl();

}



#endif /* CONFIG_SMP */



/*
@@ -2035,6 +2049,8 @@ static const struct sched_class fair_sched_class = { 


	.load_balance		= load_balance_fair,

	.move_one_task		= move_one_task_fair,

	.rq_online		= rq_online_fair,

	.rq_offline		= rq_offline_fair,

#endif



	.set_curr_task          = set_curr_task_fair,