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Commit 6f1982fe authored by Frederic Weisbecker's avatar Frederic Weisbecker Committed by Ingo Molnar
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sched/isolation: Handle the nohz_full= parameter 



We want to centralize the isolation management, done by the housekeeping
subsystem. Therefore we need to handle the nohz_full= parameter from
there.

Since nohz_full= so far has involved unbound timers, watchdog, RCU
and tilegx NAPI isolation, we keep that default behaviour.

nohz_full= will be deprecated in the future. We want to control
the isolation features from the isolcpus= parameter.

Signed-off-by: default avatarFrederic Weisbecker <frederic@kernel.org>
Acked-by: default avatarThomas Gleixner <tglx@linutronix.de>
Cc: Chris Metcalf <cmetcalf@mellanox.com>
Cc: Christoph Lameter <cl@linux.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Luiz Capitulino <lcapitulino@redhat.com>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Rik van Riel <riel@redhat.com>
Cc: Wanpeng Li <kernellwp@gmail.com>
Link: http://lkml.kernel.org/r/1509072159-31808-10-git-send-email-frederic@kernel.org


Signed-off-by: default avatarIngo Molnar <mingo@kernel.org>
parent de201559

include/linux/sched/isolation.h

+1 −0
Original line number Diff line number Diff line
@@ -10,6 +10,7 @@ enum hk_flags { 
	HK_FLAG_RCU		= (1 << 1),

	HK_FLAG_MISC		= (1 << 2),

	HK_FLAG_SCHED		= (1 << 3),

	HK_FLAG_TICK		= (1 << 4),

};



#ifdef CONFIG_CPU_ISOLATION

include/linux/tick.h

+2 −0
Original line number Diff line number Diff line
@@ -228,6 +228,7 @@ static inline void tick_dep_clear_signal(struct signal_struct *signal, 


extern void tick_nohz_full_kick_cpu(int cpu);

extern void __tick_nohz_task_switch(void);

extern void __init tick_nohz_full_setup(cpumask_var_t cpumask);

#else

static inline bool tick_nohz_full_enabled(void) { return false; }

static inline bool tick_nohz_full_cpu(int cpu) { return false; }
@@ -248,6 +249,7 @@ static inline void tick_dep_clear_signal(struct signal_struct *signal, 


static inline void tick_nohz_full_kick_cpu(int cpu) { }

static inline void __tick_nohz_task_switch(void) { }

static inline void tick_nohz_full_setup(cpumask_var_t cpumask) { }

#endif



static inline void tick_nohz_task_switch(void)

init/Kconfig

+0 −1
Original line number Diff line number Diff line
@@ -474,7 +474,6 @@ endmenu # "CPU/Task time and stats accounting" 


config CPU_ISOLATION

	bool "CPU isolation"

	depends on NO_HZ_FULL

	help

	  Make sure that CPUs running critical tasks are not disturbed by

	  any source of "noise" such as unbound workqueues, timers, kthreads...

kernel/sched/isolation.c

+30 −12
Original line number Diff line number Diff line
@@ -54,23 +54,41 @@ EXPORT_SYMBOL_GPL(housekeeping_test_cpu); 


void __init housekeeping_init(void)

{

	if (!tick_nohz_full_enabled())

	if (!housekeeping_flags)

		return;



	if (!alloc_cpumask_var(&housekeeping_mask, GFP_KERNEL)) {

		WARN(1, "NO_HZ: Can't allocate not-full dynticks cpumask\n");

		cpumask_clear(tick_nohz_full_mask);

		tick_nohz_full_running = false;

		return;

	static_branch_enable(&housekeeping_overriden);



	/* We need at least one CPU to handle housekeeping work */

	WARN_ON_ONCE(cpumask_empty(housekeeping_mask));

}



#ifdef CONFIG_NO_HZ_FULL

static int __init housekeeping_nohz_full_setup(char *str)

{

	cpumask_var_t non_housekeeping_mask;



	alloc_bootmem_cpumask_var(&non_housekeeping_mask);

	if (cpulist_parse(str, non_housekeeping_mask) < 0) {

		pr_warn("Housekeeping: Incorrect nohz_full cpumask\n");

		free_bootmem_cpumask_var(non_housekeeping_mask);

		return 0;

	}



	cpumask_andnot(housekeeping_mask,

		       cpu_possible_mask, tick_nohz_full_mask);

	alloc_bootmem_cpumask_var(&housekeeping_mask);

	cpumask_andnot(housekeeping_mask, cpu_possible_mask, non_housekeeping_mask);



	housekeeping_flags = HK_FLAG_TIMER | HK_FLAG_RCU | HK_FLAG_MISC;

	if (cpumask_empty(housekeeping_mask))

		cpumask_set_cpu(smp_processor_id(), housekeeping_mask);



	static_branch_enable(&housekeeping_overriden);

	housekeeping_flags = HK_FLAG_TICK | HK_FLAG_TIMER |

				HK_FLAG_RCU | HK_FLAG_MISC;



	/* We need at least one CPU to handle housekeeping work */

	WARN_ON_ONCE(cpumask_empty(housekeeping_mask));

	tick_nohz_full_setup(non_housekeeping_mask);



	free_bootmem_cpumask_var(non_housekeeping_mask);



	return 1;

}

__setup("nohz_full=", housekeeping_nohz_full_setup);

#endif

kernel/time/tick-sched.c

+3 −10
Original line number Diff line number Diff line
@@ -385,20 +385,13 @@ void __tick_nohz_task_switch(void) 
	local_irq_restore(flags);

}



/* Parse the boot-time nohz CPU list from the kernel parameters. */

static int __init tick_nohz_full_setup(char *str)

/* Get the boot-time nohz CPU list from the kernel parameters. */

void __init tick_nohz_full_setup(cpumask_var_t cpumask)

{

	alloc_bootmem_cpumask_var(&tick_nohz_full_mask);

	if (cpulist_parse(str, tick_nohz_full_mask) < 0) {

		pr_warn("NO_HZ: Incorrect nohz_full cpumask\n");

		free_bootmem_cpumask_var(tick_nohz_full_mask);

		return 1;

	}

	cpumask_copy(tick_nohz_full_mask, cpumask);

	tick_nohz_full_running = true;



	return 1;

}

__setup("nohz_full=", tick_nohz_full_setup);



static int tick_nohz_cpu_down(unsigned int cpu)

{