1268fbc746
Those two APIs were provided to optimize the calls of tick_nohz_idle_enter() and rcu_idle_enter() into a single irq disabled section. This way no interrupt happening in-between would needlessly process any RCU job. Now we are talking about an optimization for which benefits have yet to be measured. Let's start simple and completely decouple idle rcu and dyntick idle logics to simplify. Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com> Cc: Ingo Molnar <mingo@redhat.com> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: Peter Zijlstra <peterz@infradead.org> Reviewed-by: Josh Triplett <josh@joshtriplett.org> Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
150 lines
3.2 KiB
C
150 lines
3.2 KiB
C
/*
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* Idle daemon for PowerPC. Idle daemon will handle any action
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* that needs to be taken when the system becomes idle.
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*
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* Originally written by Cort Dougan (cort@cs.nmt.edu).
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* Subsequent 32-bit hacking by Tom Rini, Armin Kuster,
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* Paul Mackerras and others.
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*
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* iSeries supported added by Mike Corrigan <mikejc@us.ibm.com>
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*
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* Additional shared processor, SMT, and firmware support
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* Copyright (c) 2003 Dave Engebretsen <engebret@us.ibm.com>
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*
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* 32-bit and 64-bit versions merged by Paul Mackerras <paulus@samba.org>
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*
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* This program is free software; you can redistribute it and/or
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* modify it under the terms of the GNU General Public License
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* as published by the Free Software Foundation; either version
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* 2 of the License, or (at your option) any later version.
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*/
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#include <linux/sched.h>
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#include <linux/kernel.h>
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#include <linux/smp.h>
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#include <linux/cpu.h>
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#include <linux/sysctl.h>
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#include <linux/tick.h>
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#include <asm/system.h>
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#include <asm/processor.h>
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#include <asm/cputable.h>
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#include <asm/time.h>
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#include <asm/machdep.h>
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#include <asm/smp.h>
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#ifdef CONFIG_HOTPLUG_CPU
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#define cpu_should_die() cpu_is_offline(smp_processor_id())
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#else
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#define cpu_should_die() 0
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#endif
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static int __init powersave_off(char *arg)
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{
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ppc_md.power_save = NULL;
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return 0;
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}
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__setup("powersave=off", powersave_off);
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#if defined(CONFIG_PPC_PSERIES) && defined(CONFIG_TRACEPOINTS)
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static const bool idle_uses_rcu = 1;
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#else
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static const bool idle_uses_rcu;
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#endif
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/*
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* The body of the idle task.
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*/
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void cpu_idle(void)
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{
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if (ppc_md.idle_loop)
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ppc_md.idle_loop(); /* doesn't return */
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set_thread_flag(TIF_POLLING_NRFLAG);
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while (1) {
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tick_nohz_idle_enter();
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if (!idle_uses_rcu)
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rcu_idle_enter();
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while (!need_resched() && !cpu_should_die()) {
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ppc64_runlatch_off();
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if (ppc_md.power_save) {
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clear_thread_flag(TIF_POLLING_NRFLAG);
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/*
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* smp_mb is so clearing of TIF_POLLING_NRFLAG
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* is ordered w.r.t. need_resched() test.
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*/
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smp_mb();
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local_irq_disable();
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/* Don't trace irqs off for idle */
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stop_critical_timings();
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/* check again after disabling irqs */
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if (!need_resched() && !cpu_should_die())
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ppc_md.power_save();
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start_critical_timings();
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local_irq_enable();
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set_thread_flag(TIF_POLLING_NRFLAG);
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} else {
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/*
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* Go into low thread priority and possibly
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* low power mode.
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*/
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HMT_low();
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HMT_very_low();
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}
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}
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HMT_medium();
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ppc64_runlatch_on();
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if (!idle_uses_rcu)
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rcu_idle_exit();
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tick_nohz_idle_exit();
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preempt_enable_no_resched();
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if (cpu_should_die())
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cpu_die();
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schedule();
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preempt_disable();
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}
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}
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int powersave_nap;
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#ifdef CONFIG_SYSCTL
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/*
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* Register the sysctl to set/clear powersave_nap.
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*/
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static ctl_table powersave_nap_ctl_table[]={
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{
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.procname = "powersave-nap",
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.data = &powersave_nap,
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.maxlen = sizeof(int),
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.mode = 0644,
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.proc_handler = proc_dointvec,
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},
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{}
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};
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static ctl_table powersave_nap_sysctl_root[] = {
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{
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.procname = "kernel",
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.mode = 0555,
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.child = powersave_nap_ctl_table,
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},
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{}
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};
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static int __init
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register_powersave_nap_sysctl(void)
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{
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register_sysctl_table(powersave_nap_sysctl_root);
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return 0;
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}
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__initcall(register_powersave_nap_sysctl);
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#endif
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