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sched/isolation: Handle the nohz_full= parameter

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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: Frederic Weisbecker <frederic@kernel.org>
Acked-by: Thomas 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: Ingo Molnar <mingo@kernel.org>
This commit is contained in:
Frederic Weisbecker 2017-10-27 04:42:36 +02:00 committed by Ingo Molnar
parent de201559df
commit 6f1982fedd
5 changed files with 37 additions and 24 deletions
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1
include/linux/sched/isolation.h
View File

@ -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

2
include/linux/tick.h
View File

@ -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)

1
init/Kconfig
View File

@ -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...

44
kernel/sched/isolation.c
View File

@ -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;
}
cpumask_andnot(housekeeping_mask,
cpu_possible_mask, tick_nohz_full_mask);
housekeeping_flags = HK_FLAG_TIMER | HK_FLAG_RCU | HK_FLAG_MISC;
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;
}
alloc_bootmem_cpumask_var(&housekeeping_mask);
cpumask_andnot(housekeeping_mask, cpu_possible_mask, non_housekeeping_mask);
if (cpumask_empty(housekeeping_mask))
cpumask_set_cpu(smp_processor_id(), housekeeping_mask);
housekeeping_flags = HK_FLAG_TICK | HK_FLAG_TIMER |
HK_FLAG_RCU | HK_FLAG_MISC;
tick_nohz_full_setup(non_housekeeping_mask);
free_bootmem_cpumask_var(non_housekeeping_mask);
return 1;
}
__setup("nohz_full=", housekeeping_nohz_full_setup);
#endif

13
kernel/time/tick-sched.c
View File

@ -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)
{