Start with a very simple interface to define full dynticks CPU:
use a boot time option defined cpumask through the "full_nohz="
kernel parameter.
Make sure you keep at least one CPU outside this range to handle
the timekeeping.
Also full_nohz= must match rcu_nocb= value.
Suggested-by: Paul E. McKenney <paul...@linux.vnet.ibm.com>
Signed-off-by: Frederic Weisbecker <fweis...@gmail.com>
Cc: Alessio Igor Bogani <abog...@kernel.org>
Cc: Andrew Morton <a...@linux-foundation.org>
Cc: Avi Kivity <a...@redhat.com>
Cc: Chris Metcalf <cmetc...@tilera.com>
Cc: Christoph Lameter <c...@linux.com>
Cc: Geoff Levand <ge...@infradead.org>
Cc: Gilad Ben Yossef <gi...@benyossef.com>
Cc: Hakan Akkan <hakanak...@gmail.com>
Cc: Ingo Molnar <mi...@kernel.org>
Cc: Paul E. McKenney <paul...@linux.vnet.ibm.com>
Cc: Paul Gortmaker <paul.gortma...@windriver.com>
Cc: Peter Zijlstra <pet...@infradead.org>
Cc: Steven Rostedt <rost...@goodmis.org>
Cc: Thomas Gleixner <t...@linutronix.de>
---
include/linux/tick.h | 7 +++++++
kernel/time/Kconfig | 9 +++++++++
kernel/time/tick-sched.c | 23 +++++++++++++++++++++++
3 files changed, 39 insertions(+), 0 deletions(-)
diff --git a/include/linux/tick.h b/include/linux/tick.h
index 553272e..2d4f6f0 100644
--- a/include/linux/tick.h
+++ b/include/linux/tick.h
@@ -157,6 +157,13 @@ static inline u64 get_cpu_idle_time_us(int cpu, u64
*unused) { return -1; }
static inline u64 get_cpu_iowait_time_us(int cpu, u64 *unused) { return -1; }
# endif /* !NO_HZ */
+#ifdef CONFIG_NO_HZ_FULL
+int tick_nohz_full_cpu(int cpu);
+#else
+static inline int tick_nohz_full_cpu(int cpu) { return 0; }
+#endif
+
+
# ifdef CONFIG_CPU_IDLE_GOV_MENU
extern void menu_hrtimer_cancel(void);
# else
diff --git a/kernel/time/Kconfig b/kernel/time/Kconfig
index 8601f0d..0a1bc72 100644
--- a/kernel/time/Kconfig
+++ b/kernel/time/Kconfig
@@ -70,6 +70,15 @@ config NO_HZ
only trigger on an as-needed basis both when the system is
busy and when the system is idle.
+config NO_HZ_FULL
+ bool "Full tickless system"
+ depends on NO_HZ && RCU_USER_QS && VIRT_CPU_ACCOUNTING_GEN &&
RCU_NOCB_CPU
+ select CONTEXT_TRACKING_FORCE
+ help
+ Try to be tickless everywhere, not just in idle. (You need
+ to fill up the full_nohz_mask boot parameter).
+
+
config HIGH_RES_TIMERS
bool "High Resolution Timer Support"
depends on !ARCH_USES_GETTIMEOFFSET && GENERIC_CLOCKEVENTS
diff --git a/kernel/time/tick-sched.c b/kernel/time/tick-sched.c
index ad0e6fa..fac9ba4 100644
--- a/kernel/time/tick-sched.c
+++ b/kernel/time/tick-sched.c
@@ -142,6 +142,29 @@ static void tick_sched_handle(struct tick_sched *ts,
struct pt_regs *regs)
profile_tick(CPU_PROFILING);
}
+#ifdef CONFIG_NO_HZ_FULL
+static cpumask_var_t full_nohz_mask;
+bool have_full_nohz_mask;
+
+int tick_nohz_full_cpu(int cpu)
+{
+ if (!have_full_nohz_mask)
+ return 0;
+
+ return cpumask_test_cpu(cpu, full_nohz_mask);
+}
+
+/* Parse the boot-time nohz CPU list from the kernel parameters. */
+static int __init tick_nohz_full_setup(char *str)
+{
+ alloc_bootmem_cpumask_var(&full_nohz_mask);
+ have_full_nohz_mask = true;
+ cpulist_parse(str, full_nohz_mask);
+ return 1;
+}
+__setup("full_nohz=", tick_nohz_full_setup);
+#endif
+
/*
* NOHZ - aka dynamic tick functionality
*/
--
1.7.5.4
--
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