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Subject[PATCH 3/3] nohz: New option to default all CPUs in full dynticks range
Date
Provide a new kernel config that defaults all CPUs to be part
of the full dynticks range, except the boot one for timekeeping.

This default setting is overriden by the nohz_full= boot option
if passed by the user.

This is helpful for those who don't need a finegrained range
of full dynticks CPU and also for automated testing.

Suggested-by: Ingo Molnar <mingo@kernel.org>
Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Chris Metcalf <cmetcalf@tilera.com>
Cc: Christoph Lameter <cl@linux.com>
Cc: Geoff Levand <geoff@infradead.org>
Cc: Gilad Ben Yossef <gilad@benyossef.com>
Cc: Hakan Akkan <hakanakkan@gmail.com>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Kevin Hilman <khilman@linaro.org>
Cc: Li Zhong <zhong@linux.vnet.ibm.com>
Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: Paul Gortmaker <paul.gortmaker@windriver.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
---
kernel/time/Kconfig | 10 ++++++++++
kernel/time/tick-sched.c | 23 +++++++++++++++++++++--
2 files changed, 31 insertions(+), 2 deletions(-)

diff --git a/kernel/time/Kconfig b/kernel/time/Kconfig
index 358d601..99c3f13 100644
--- a/kernel/time/Kconfig
+++ b/kernel/time/Kconfig
@@ -128,6 +128,16 @@ config NO_HZ_FULL

endchoice

+config NO_HZ_FULL_ALL
+ bool "Full dynticks system on all CPUs by default"
+ depends on NO_HZ_FULL
+ help
+ If the user doesn't pass the nohz_full boot option to
+ define the range of full dynticks CPUs, consider that all
+ CPUs in the system are full dynticks by default.
+ Note the boot CPU will still be kept outside the range to
+ handle the timekeeping duty.
+
config NO_HZ
bool "Old Idle dynticks config"
depends on !ARCH_USES_GETTIMEOFFSET && GENERIC_CLOCKEVENTS
diff --git a/kernel/time/tick-sched.c b/kernel/time/tick-sched.c
index d71a5f2..a76e090 100644
--- a/kernel/time/tick-sched.c
+++ b/kernel/time/tick-sched.c
@@ -203,12 +203,31 @@ static int __cpuinit tick_nohz_cpu_down_callback(struct notifier_block *nfb,
*/
static char __initdata nohz_full_buf[NR_CPUS + 1];

+static int tick_nohz_init_all(void)
+{
+ int err = -1;
+
+#ifdef CONFIG_NO_HZ_FULL_ALL
+ if (!alloc_cpumask_var(&nohz_full_mask, GFP_KERNEL)) {
+ pr_err("NO_HZ: Can't allocate full dynticks cpumask\n");
+ return err;
+ }
+ err = 0;
+ cpumask_setall(nohz_full_mask);
+ cpumask_clear_cpu(smp_processor_id(), nohz_full_mask);
+ have_nohz_full_mask = true;
+#endif
+ return err;
+}
+
void __init tick_nohz_init(void)
{
int cpu;

- if (!have_nohz_full_mask)
- return;
+ if (!have_nohz_full_mask) {
+ if (tick_nohz_init_all() < 0)
+ return;
+ }

cpu_notifier(tick_nohz_cpu_down_callback, 0);

--
1.7.5.4


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