Valid arguments: on, off
Default: on
+ nohz_extended= [KNL,BOOT]
+ In kernels built with CONFIG_NO_HZ_EXTENDED=y, set
+ the specified list of CPUs whose tick will be stopped
+ whenever possible. You need to keep at least one online
+ CPU outside the range to maintain the timekeeping.
+
noiotrap [SH] Disables trapped I/O port accesses.
noirqdebug [X86-32] Disables the code which attempts to detect and
only trigger on an as-needed basis both when the system is
busy and when the system is idle.
+config NO_HZ_EXTENDED
+ bool "Full dynticks system"
+ depends on NO_HZ && RCU_USER_QS && VIRT_CPU_ACCOUNTING_GEN && RCU_NOCB_CPU && SMP
+ select CONTEXT_TRACKING_FORCE
+ help
+ Adaptively try to shutdown the tick whenever possible, even when
+ the CPU is running tasks. Typically this requires running a single
+ task on the CPU. Chances for running tickless are maximized when
+ the task mostly runs in userspace and has few kernel activity.
+
+ You need to fill up the nohz_extended boot parameter with the
+ desired range of dynticks CPUs.
+
+ This is implemented at the expense of some overhead in user <-> kernel
+ transitions: syscalls, exceptions and interrupts. Even when it's
+ dynamically off.
+
+ Say N.
+
config HIGH_RES_TIMERS
bool "High Resolution Timer Support"
depends on !ARCH_USES_GETTIMEOFFSET && GENERIC_CLOCKEVENTS
profile_tick(CPU_PROFILING);
}
+#ifdef CONFIG_NO_HZ_EXTENDED
+static cpumask_var_t nohz_extended_mask;
+bool have_nohz_extended_mask;
+
+int tick_nohz_extended_cpu(int cpu)
+{
+ if (!have_nohz_extended_mask)
+ return 0;
+
+ return cpumask_test_cpu(cpu, nohz_extended_mask);
+}
+
+/* Parse the boot-time nohz CPU list from the kernel parameters. */
+static int __init tick_nohz_extended_setup(char *str)
+{
+ alloc_bootmem_cpumask_var(&nohz_extended_mask);
+ if (cpulist_parse(str, nohz_extended_mask) < 0)
+ pr_warning("NOHZ: Incorrect nohz_extended cpumask\n");
+ else
+ have_nohz_extended_mask = true;
+ return 1;
+}
+__setup("nohz_extended=", tick_nohz_extended_setup);
+
+static int __init init_tick_nohz_extended(void)
+{
+ cpumask_var_t online_nohz;
+ int cpu;
+
+ if (!have_nohz_extended_mask)
+ return 0;
+
+ if (!zalloc_cpumask_var(&online_nohz, GFP_KERNEL)) {
+ pr_warning("NO_HZ: Not enough memory to check extended nohz mask\n");
+ return -ENOMEM;
+ }
+
+ /*
+ * CPUs can probably not be concurrently offlined on initcall time.
+ * But we are paranoid, aren't we?
+ */
+ get_online_cpus();
+
+ /* Ensure we keep a CPU outside the dynticks range for timekeeping */
+ cpumask_and(online_nohz, cpu_online_mask, nohz_extended_mask);
+ if (cpumask_equal(online_nohz, cpu_online_mask)) {
+ cpu = cpumask_any(cpu_online_mask);
+ pr_warning("NO_HZ: Must keep at least one online CPU "
+ "out of nohz_extended range\n");
+ pr_warning("NO_HZ: Clearing %d from nohz_extended range\n", cpu);
+ cpumask_clear_cpu(cpu, nohz_extended_mask);
+ }
+ put_online_cpus();
+ free_cpumask_var(online_nohz);
+
+ return 0;
+}
+core_initcall(init_tick_nohz_extended);
+#else
+#define have_nohz_extended_mask (0)
+#endif
+
/*
* NOHZ - aka dynamic tick functionality
*/