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Subject[tip:sched/core] sched/isolation: Handle the nohz_full= parameter
Commit-ID:  6f1982fedd59856bcc42a9b521be4c3ffd2f60a7
Gitweb: https://git.kernel.org/tip/6f1982fedd59856bcc42a9b521be4c3ffd2f60a7
Author: Frederic Weisbecker <frederic@kernel.org>
AuthorDate: Fri, 27 Oct 2017 04:42:36 +0200
Committer: Ingo Molnar <mingo@kernel.org>
CommitDate: Fri, 27 Oct 2017 09:55:30 +0200

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: 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>
---
include/linux/sched/isolation.h | 1 +
include/linux/tick.h | 2 ++
init/Kconfig | 1 -
kernel/sched/isolation.c | 42 +++++++++++++++++++++++++++++------------
kernel/time/tick-sched.c | 13 +++----------
5 files changed, 36 insertions(+), 23 deletions(-)

diff --git a/include/linux/sched/isolation.h b/include/linux/sched/isolation.h
index 9bb753e..e53cfa9 100644
--- a/include/linux/sched/isolation.h
+++ b/include/linux/sched/isolation.h
@@ -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
diff --git a/include/linux/tick.h b/include/linux/tick.h
index 68afc09..e2a163a 100644
--- a/include/linux/tick.h
+++ b/include/linux/tick.h
@@ -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)
diff --git a/init/Kconfig b/init/Kconfig
index 6f52e6f..f8564df 100644
--- a/init/Kconfig
+++ b/init/Kconfig
@@ -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...
diff --git a/kernel/sched/isolation.c b/kernel/sched/isolation.c
index 37a138a..1f61e44 100644
--- a/kernel/sched/isolation.c
+++ b/kernel/sched/isolation.c
@@ -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
diff --git a/kernel/time/tick-sched.c b/kernel/time/tick-sched.c
index 27d7d52..69f3dbe 100644
--- a/kernel/time/tick-sched.c
+++ b/kernel/time/tick-sched.c
@@ -385,20 +385,13 @@ out:
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)
{
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