[PATCH] i386 no idle HZ aka Dynticks 051203

Here is an updated complete patch implementing no idle hz ticks
aka dynticks for i386.

Changes in this version:
-Significant rework separating out architecture dependent portions
-Bugfixes with respect to timers firing off at load
-Added dyn_early_reprogram API to allow other code to interact with
dynticks for benefit (eg ACPI) and to perform normal timers
-Make bus mastering detection code dynticks smart
-Numerous cleanups
-Latest version of timertop
-Sanity limits on max and min ticks to skip

Split out patches, timertop and pmstats utilities and latest patch available
here:
http://ck.kolivas.org/patches/dyn-ticks/

Cheers,
Con

---
Implement i386 no-idle-hz aka dynticks rolled up patch.

Original code by Tony Lindgen <[email protected]>,
Tuukka Tikkanen <[email protected]>,
Srivatsa Vaddagiri <[email protected]> and
Daniel Petrini <[email protected]>.

Rewritten and updated by Con Kolivas <[email protected]>

Signed-off-by: Con Kolivas <[email protected]>

 arch/i386/Kconfig                       |   16 ++
 arch/i386/defconfig                     |    1
 arch/i386/kernel/Makefile               |    1
 arch/i386/kernel/apic.c                 |   33 ++++
 arch/i386/kernel/dyn-tick.c             |  143 ++++++++++++++++++
 arch/i386/kernel/io_apic.c              |   26 ++-
 arch/i386/kernel/irq.c                  |    4
 arch/i386/kernel/process.c              |    4
 arch/i386/kernel/smp.c                  |    9 +
 arch/i386/kernel/time.c                 |   19 +-
 arch/i386/kernel/timers/timer_cyclone.c |    4
 arch/i386/kernel/timers/timer_hpet.c    |    4
 arch/i386/kernel/timers/timer_none.c    |    3
 arch/i386/kernel/timers/timer_pit.c     |   35 ++++
 arch/i386/kernel/timers/timer_pm.c      |   32 +---
 arch/i386/kernel/timers/timer_tsc.c     |   62 +++-----
 drivers/acpi/Kconfig                    |    2
 drivers/acpi/processor_idle.c           |   28 +++
 include/asm-i386/apic.h                 |    2
 include/asm-i386/dyn-tick.h             |   65 ++++++++
 include/asm-i386/timer.h                |   43 +++++
 include/linux/dyn-tick.h                |   87 +++++++++++
 include/linux/timer.h                   |    1
 kernel/Makefile                         |    2
 kernel/dyn-tick.c                       |  246 ++++++++++++++++++++++++++++++++
 kernel/timer.c                          |   10 +
 kernel/timer_top.c                      |  237 ++++++++++++++++++++++++++++++
 lib/Kconfig.debug                       |   13 +
 28 files changed, 1064 insertions(+), 68 deletions(-)

Index: linux-2.6.15-rc5-dt/include/linux/dyn-tick.h
===================================================================
--- /dev/null
+++ linux-2.6.15-rc5-dt/include/linux/dyn-tick.h
@@ -0,0 +1,87 @@
+/*
+ * linux/include/linux/dyn-tick.h
+ *
+ * Copyright (C) 2004 Nokia Corporation
+ * Written by Tony Lindgen <[email protected]> and
+ * Tuukka Tikkanen <[email protected]>
+ * Rewritten by Con Kolivas <[email protected]>
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2 as
+ * published by the Free Software Foundation.
+ */
+
+#ifndef _DYN_TICK_TIMER_H
+#define _DYN_TICK_TIMER_H
+
+#include <linux/interrupt.h>
+
+#define DYN_TICK_SKIPPING	(1 << 2)
+#define DYN_TICK_ENABLED	(1 << 1)
+#define DYN_TICK_SUITABLE	(1 << 0)
+
+/* Ok to be 0 but there is no point reprogramming for <2ms intervals */
+#define DYN_TICK_MIN_SKIP	(HZ / 500)
+/* Baseline tick rate of slowest timers in kernel */
+#define DYN_TICK_MAX_SKIP	(HZ / 5)
+
+struct dyn_tick_timer {
+	spinlock_t lock;
+
+	int (*arch_init) (void);	/* dyn_tick init */
+	int (*arch_enable)(void);	/* Enables dynamic tick */
+	int (*arch_disable)(void);	/* Disables dynamic tick */
+	void (*arch_reprogram)(unsigned long); /* Reprograms the timer */
+	int (*arch_handler)(int, void *, struct pt_regs *);
+	void (*arch_all_cpus_idle) (int);
+
+	unsigned short state;		/* Current state */
+	unsigned int min_skip;		/* Max number of ticks to skip */
+	unsigned int max_skip;		/* Max number of ticks to skip */
+	unsigned long skip_tick;	/* Current tick we started skipping */
+	unsigned long last_skip;	/* Last tick we started skipping */
+	unsigned long skip;		/* Ticks we're currently skipping */
+};
+
+extern struct dyn_tick_timer *dyn_tick;
+extern spinlock_t *dyn_tick_lock;
+
+extern void dyn_tick_register(struct dyn_tick_timer *new_timer);
+
+#ifdef CONFIG_NO_IDLE_HZ
+extern int dyn_tick_enabled(void);
+extern void timer_dyn_reprogram(void);
+extern void dyn_early_reprogram(unsigned int delta);
+extern void set_dyn_tick_limits(unsigned int max_skip, unsigned int min_skip);
+
+#ifdef CONFIG_TIMER_INFO
+extern int account_timer(unsigned long function, unsigned long data);
+#else
+static inline int account_timer(unsigned long function, unsigned long data)
+{
+	return 0;
+}
+#endif
+
+#else	/* CONFIG_NO_IDLE_HZ */
+static inline int dyn_tick_enabled(void)
+{
+	return 0;
+}
+
+static inline void set_dyn_tick_limits(unsigned int max_skip,
+	unsigned int min_skip)
+{
+}
+
+static inline void dyn_early_reprogram(unsigned int delta)
+{
+}
+
+static inline int account_timer(unsigned long function, unsigned long data)
+{
+	return 0;
+}
+#endif	/* CONFIG_NO_IDLE_HZ */
+
+#endif	/* _DYN_TICK_TIMER_H */
Index: linux-2.6.15-rc5-dt/include/linux/timer.h
===================================================================
--- linux-2.6.15-rc5-dt.orig/include/linux/timer.h
+++ linux-2.6.15-rc5-dt/include/linux/timer.h
@@ -97,5 +97,6 @@ static inline void add_timer(struct time
 extern void init_timers(void);
 extern void run_local_timers(void);
 extern void it_real_fn(unsigned long);
+extern void conditional_run_local_timers(void);
 
 #endif
Index: linux-2.6.15-rc5-dt/kernel/dyn-tick.c
===================================================================
--- /dev/null
+++ linux-2.6.15-rc5-dt/kernel/dyn-tick.c
@@ -0,0 +1,246 @@
+/*
+ * linux/kernel/dyn-tick.c
+ *
+ * Generic dynamic tick timer support
+ *
+ * Copyright (C) 2004 Nokia Corporation
+ * Written by Tony Lindgen <[email protected]> and
+ * Tuukka Tikkanen <[email protected]>
+ * Rewritten by Con Kolivas <[email protected]>
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2 as
+ * published by the Free Software Foundation.
+ */
+
+#include <linux/version.h>
+#include <linux/config.h>
+#include <linux/kernel.h>
+#include <linux/init.h>
+#include <linux/module.h>
+#include <linux/sysdev.h>
+#include <linux/interrupt.h>
+#include <linux/cpumask.h>
+#include <linux/pm.h>
+#include <linux/dyn-tick.h>
+#include <linux/rcupdate.h>
+#include <asm/dyn-tick.h>
+
+#define DYN_TICK_VERSION	"051203"
+
+EXPORT_SYMBOL(dyn_tick);
+
+int dyn_tick_enabled(void)
+{
+	return (dyn_tick->state & DYN_TICK_ENABLED);
+}
+
+EXPORT_SYMBOL(dyn_tick_enabled);
+
+static inline int dyn_tick_suitable(void)
+{
+	return (dyn_tick->state & DYN_TICK_SUITABLE);
+}
+
+/*
+ * do_dyn_reprogram does the actual reprogramming. We should have already
+ * checked that the tick chosen is suitable and xtime_lock and dyn_tick->lock
+ * must be held, and interrupts disabled.
+ */
+static void do_dyn_reprogram(unsigned int delta)
+{
+	dyn_tick->last_skip = dyn_tick->skip_tick;
+	dyn_tick->skip_tick = jiffies;
+	dyn_tick->skip = delta;
+	dyn_tick->arch_reprogram(jiffies + delta);
+}
+
+/*
+ * Arch independent code needed to reprogram next timer interrupt.
+ * Gets called, with IRQs disabled, from cpu_idle() before entering idle loop.
+ * Significant contention is possible so avoid spinning on xtime_lock and do
+ * not reprogram timers instead.
+ */
+void timer_dyn_reprogram(void)
+{
+	int cpu;
+	unsigned int delta;
+
+	if (!dyn_tick_enabled())
+		return;
+
+	cpu = smp_processor_id();
+	if (rcu_pending(cpu) || local_softirq_pending())
+		return;
+
+	/* Check if we can start skipping ticks */
+	if (unlikely(!write_tryseqlock(&xtime_lock)))
+		return;
+
+	delta = next_timer_interrupt() - jiffies;
+	if (delta > dyn_tick->max_skip)
+		delta = dyn_tick->max_skip;
+
+	if (delta > dyn_tick->min_skip) {
+		int idle_time = 0;
+
+		if (dyn_tick->skip_tick + dyn_tick->skip == jiffies)
+			idle_time = dyn_tick->skip;
+		spin_lock(&dyn_tick->lock);
+
+		do_dyn_reprogram(delta);
+
+		cpu_set(cpu, nohz_cpu_mask);
+		if (cpus_equal(nohz_cpu_mask, cpu_online_map))
+			dyn_tick->arch_all_cpus_idle(idle_time);
+
+		spin_unlock(&dyn_tick->lock);
+	}
+
+	write_sequnlock(&xtime_lock);
+}
+
+/*
+ * dyn_early_reprogram is used to reprogram an earlier tick than is currently
+ * set by timer_dyn_reprogram. It will schedule a mandatory timer tick rather
+ * than reprogramming only if dyn_tick->lock is not held.
+ * dyn_early_reprogram allows other code such as the acpi idle code to
+ * program an earlier tick than the one already chosen by timer_dyn_reprogram.
+ * It only reprograms it if the tick is earlier than the next one planned.
+ */
+void dyn_early_reprogram(unsigned int delta)
+{
+	unsigned long flags, tick = jiffies + delta;
+
+	if (tick >= dyn_tick->last_skip + dyn_tick->skip)
+		return;
+
+	write_seqlock_irqsave(&xtime_lock, flags);
+	spin_lock(&dyn_tick->lock);
+	do_dyn_reprogram(delta);
+	spin_unlock(&dyn_tick->lock);
+	write_sequnlock_irqrestore(&xtime_lock, flags);
+}
+
+void set_dyn_tick_limits(unsigned int max_skip, unsigned int min_skip)
+{
+	if (max_skip > DYN_TICK_MAX_SKIP)
+		max_skip = DYN_TICK_MAX_SKIP;
+	if (!dyn_tick->max_skip || max_skip < dyn_tick->max_skip)
+		dyn_tick->max_skip = max_skip;
+	if (min_skip < DYN_TICK_MIN_SKIP)
+		min_skip = DYN_TICK_MIN_SKIP;
+	if (min_skip > dyn_tick->min_skip)
+		dyn_tick->min_skip = min_skip;
+}
+
+void __init dyn_tick_register(struct dyn_tick_timer *arch_timer)
+{
+	dyn_tick = arch_timer;
+	printk(KERN_INFO "dyn-tick: Registering dynamic tick timer v%s\n",
+	       DYN_TICK_VERSION);
+}
+
+/* Default to enabled */
+static int __initdata dyntick_autoenable = 1;
+
+/*
+ * Command line options.
+ *
+ *  dyntick=[enable|disable]
+ */
+static int __init dyntick_setup(char *options)
+{
+	if (!options)
+		return 0;
+
+	if (!strncmp(options, "enable", 5))
+		dyntick_autoenable = 1;
+	if (!strncmp(options, "disable", 6))
+		dyntick_autoenable = 0;
+
+	return 0;
+}
+
+__setup("dyntick=", dyntick_setup);
+
+/*
+ * Sysfs interface.
+ *
+ * Usually situated at:
+ *  /sys/devices/system/timer/timer0/dyn_tick
+ */
+extern struct sys_device device_timer;
+
+static ssize_t timer_show_dyn_tick(struct sys_device *dev, char *buf)
+{
+	return sprintf(buf, "%i\n", dyn_tick_enabled());
+}
+
+static ssize_t timer_set_dyn_tick(struct sys_device *dev, const char *buf,
+				  size_t count)
+{
+	unsigned long flags;
+	unsigned int enable = simple_strtoul(buf, NULL, 2);
+	int ret = -ENODEV;
+
+	write_seqlock_irqsave(&xtime_lock, flags);
+	if (enable) {
+		ret = dyn_tick->arch_enable();
+		if (ret == 0)
+			dyn_tick->state |= DYN_TICK_ENABLED;
+	} else {
+		ret = dyn_tick->arch_disable();
+		if (ret == 0)
+			dyn_tick->state &= ~DYN_TICK_ENABLED;
+	}
+	write_sequnlock_irqrestore(&xtime_lock, flags);
+
+	return count;
+}
+
+static SYSDEV_ATTR(dyn_tick, 0644, timer_show_dyn_tick, timer_set_dyn_tick);
+
+static int __init init_dyn_tick_sysfs(void)
+{
+	int ret = sysdev_create_file(&device_timer, &attr_dyn_tick);
+
+	return ret;
+}
+
+device_initcall(init_dyn_tick_sysfs);
+
+/*
+ * Init functions
+ *
+ * We need to initialise dynamic tick after calibrate delay
+ */
+static int __init dyn_tick_late_init(void)
+{
+	int ret;
+
+	if (dyn_tick == NULL || dyn_tick->arch_init == NULL ||
+	    !dyn_tick_suitable()) {
+		printk(KERN_ERR "dyn-tick: No suitable timer found\n");
+		return -ENODEV;
+	}
+
+	if ((ret = dyn_tick->arch_init())) {
+		printk(KERN_ERR "dyn-tick: Init failed\n");
+		return -ENODEV;
+	}
+
+	if (!ret && dyntick_autoenable) {
+		dyn_tick->state |= DYN_TICK_ENABLED;
+		printk(KERN_INFO "dyn-tick: Timer using dynamic tick\n");
+	} else
+		printk(KERN_INFO "dyn-tick: Timer not enabled during boot\n");
+
+	dyn_tick->skip_tick = 0;
+	dyn_tick->last_skip = 0;
+	dyn_tick->skip = 0;
+
+	return ret;
+}
+
+late_initcall(dyn_tick_late_init);
Index: linux-2.6.15-rc5-dt/kernel/Makefile
===================================================================
--- linux-2.6.15-rc5-dt.orig/kernel/Makefile
+++ linux-2.6.15-rc5-dt/kernel/Makefile
@@ -32,6 +32,8 @@ obj-$(CONFIG_GENERIC_HARDIRQS) += irq/
 obj-$(CONFIG_CRASH_DUMP) += crash_dump.o
 obj-$(CONFIG_SECCOMP) += seccomp.o
 obj-$(CONFIG_RCU_TORTURE_TEST) += rcutorture.o
+obj-$(CONFIG_NO_IDLE_HZ) += dyn-tick.o
+obj-$(CONFIG_TIMER_INFO) += timer_top.o
 
 ifneq ($(CONFIG_SCHED_NO_NO_OMIT_FRAME_POINTER),y)
 # According to Alan Modra <[email protected]>, the -fno-omit-frame-pointer is
Index: linux-2.6.15-rc5-dt/kernel/timer.c
===================================================================
--- linux-2.6.15-rc5-dt.orig/kernel/timer.c
+++ linux-2.6.15-rc5-dt/kernel/timer.c
@@ -33,6 +33,7 @@
 #include <linux/posix-timers.h>
 #include <linux/cpu.h>
 #include <linux/syscalls.h>
+#include <linux/dyn-tick.h>
 
 #include <asm/uaccess.h>
 #include <asm/unistd.h>
@@ -540,6 +541,8 @@ found:
 				expires = nte->expires;
 		}
 	}
+	account_timer((unsigned long)nte->function, nte->data);
+
 	spin_unlock(&base->t_base.lock);
 	return expires;
 }
@@ -869,6 +872,13 @@ void run_local_timers(void)
 	raise_softirq(TIMER_SOFTIRQ);
 }
 
+void conditional_run_local_timers(void)
+{
+	tvec_base_t *base  = &__get_cpu_var(tvec_bases);
+
+	if (base->timer_jiffies != jiffies)
+		run_local_timers();
+}
 /*
  * Called by the timer interrupt. xtime_lock must already be taken
  * by the timer IRQ!
Index: linux-2.6.15-rc5-dt/drivers/acpi/Kconfig
===================================================================
--- linux-2.6.15-rc5-dt.orig/drivers/acpi/Kconfig
+++ linux-2.6.15-rc5-dt/drivers/acpi/Kconfig
@@ -301,6 +301,8 @@ config X86_PM_TIMER
 	  voltage scaling, unlike the commonly used Time Stamp Counter
 	  (TSC) timing source.
 
+	  This timer is selected by dyntick (NO_IDLE_HZ).
+
 	  So, if you see messages like 'Losing too many ticks!' in the
 	  kernel logs, and/or you are using this on a notebook which
 	  does not yet have an HPET, you should say "Y" here.
Index: linux-2.6.15-rc5-dt/arch/i386/defconfig
===================================================================
--- linux-2.6.15-rc5-dt.orig/arch/i386/defconfig
+++ linux-2.6.15-rc5-dt/arch/i386/defconfig
@@ -91,6 +91,7 @@ CONFIG_X86_INTEL_USERCOPY=y
 CONFIG_X86_USE_PPRO_CHECKSUM=y
 # CONFIG_HPET_TIMER is not set
 # CONFIG_HPET_EMULATE_RTC is not set
+# CONFIG_NO_IDLE_HZ is not set
 CONFIG_SMP=y
 CONFIG_NR_CPUS=8
 CONFIG_SCHED_SMT=y
Index: linux-2.6.15-rc5-dt/arch/i386/Kconfig
===================================================================
--- linux-2.6.15-rc5-dt.orig/arch/i386/Kconfig
+++ linux-2.6.15-rc5-dt/arch/i386/Kconfig
@@ -173,6 +173,22 @@ config HPET_EMULATE_RTC
 	depends on HPET_TIMER && RTC=y
 	default y
 
+config NO_IDLE_HZ
+	bool "Dynamic Tick Timer - Skip timer ticks during idle"
+	depends on EXPERIMENTAL
+	select X86_PM_TIMER
+	help
+	  This option enables support for skipping timer ticks when the
+	  processor is idle. During system load, timer is continuous.
+	  This option saves power, as it allows the system to stay in
+	  idle mode longer. Currently the only supported timer is ACPI PM
+	  timer.
+
+	  Note that you can disable dynamic tick timer either by
+	  passing dyntick=disable command line option, or via sysfs:
+
+	  # echo 0 > /sys/devices/system/timer/timer0/dyn_tick
+
 config SMP
 	bool "Symmetric multi-processing support"
 	---help---
Index: linux-2.6.15-rc5-dt/arch/i386/kernel/apic.c
===================================================================
--- linux-2.6.15-rc5-dt.orig/arch/i386/kernel/apic.c
+++ linux-2.6.15-rc5-dt/arch/i386/kernel/apic.c
@@ -26,6 +26,7 @@
 #include <linux/kernel_stat.h>
 #include <linux/sysdev.h>
 #include <linux/cpu.h>
+#include <linux/dyn-tick.h>
 
 #include <asm/atomic.h>
 #include <asm/smp.h>
@@ -35,6 +36,7 @@
 #include <asm/arch_hooks.h>
 #include <asm/hpet.h>
 #include <asm/i8253.h>
+#include <asm/dyn-tick.h>
 
 #include <mach_apic.h>
 
@@ -932,6 +934,9 @@ void (*wait_timer_tick)(void) __devinitd
 
 #define APIC_DIVISOR 16
 
+static u32 apic_timer_val __read_mostly;
+#define APIC_TIMER_VAL	((apic_timer_val) / (HZ))
+
 static void __setup_APIC_LVTT(unsigned int clocks)
 {
 	unsigned int lvtt_value, tmp_value, ver;
@@ -950,7 +955,9 @@ static void __setup_APIC_LVTT(unsigned i
 				& ~(APIC_TDR_DIV_1 | APIC_TDR_DIV_TMBASE))
 				| APIC_TDR_DIV_16);
 
-	apic_write_around(APIC_TMICT, clocks/APIC_DIVISOR);
+	apic_timer_val = clocks * HZ / APIC_DIVISOR;
+
+	apic_write_around(APIC_TMICT, APIC_TIMER_VAL);
 }
 
 static void __devinit setup_APIC_timer(unsigned int clocks)
@@ -969,6 +976,17 @@ static void __devinit setup_APIC_timer(u
 	local_irq_restore(flags);
 }
 
+/* Used by NO_IDLE_HZ to skip ticks on idle CPUs */
+void reprogram_apic_timer(unsigned long count)
+{
+	unsigned long flags;
+
+	count = count * apic_timer_val / HZ;
+	local_irq_save(flags);
+	apic_write_around(APIC_TMICT, count);
+	local_irq_restore(flags);
+}
+
 /*
  * In this function we calibrate APIC bus clocks to the external
  * timer. Unfortunately we cannot use jiffies and the timer irq
@@ -1064,6 +1082,10 @@ void __init setup_boot_APIC_clock(void)
 	 */
 	setup_APIC_timer(calibration_result);
 
+	if (setup_dyn_tick_use_apic(calibration_result))
+		set_dyn_tick_limits((0xFFFFFFFF / calibration_result) *
+			APIC_DIVISOR, 0);
+
 	local_irq_restore(flags);
 }
 
@@ -1202,6 +1224,9 @@ fastcall void smp_apic_timer_interrupt(s
 	 * interrupt lock, which is the WrongThing (tm) to do.
 	 */
 	irq_enter();
+
+	dyn_tick_interrupt(regs);
+
 	smp_local_timer_interrupt(regs);
 	irq_exit();
 }
@@ -1214,6 +1239,9 @@ fastcall void smp_spurious_interrupt(str
 	unsigned long v;
 
 	irq_enter();
+
+	dyn_tick_interrupt(regs);
+
 	/*
 	 * Check if this really is a spurious interrupt and ACK it
 	 * if it is a vectored one.  Just in case...
@@ -1238,6 +1266,9 @@ fastcall void smp_error_interrupt(struct
 	unsigned long v, v1;
 
 	irq_enter();
+
+	dyn_tick_interrupt(regs);
+
 	/* First tickle the hardware, only then report what went on. -- REW */
 	v = apic_read(APIC_ESR);
 	apic_write(APIC_ESR, 0);
Index: linux-2.6.15-rc5-dt/arch/i386/kernel/dyn-tick.c
===================================================================
--- /dev/null
+++ linux-2.6.15-rc5-dt/arch/i386/kernel/dyn-tick.c
@@ -0,0 +1,143 @@
+/*
+ * linux/arch/i386/kernel/dyn-tick.c
+ *
+ * Copyright (C) 2004 Nokia Corporation
+ * Written by Tony Lindgen <[email protected]> and
+ * Tuukka Tikkanen <[email protected]>
+ * Rewritten by Con Kolivas <[email protected]>
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2 as
+ * published by the Free Software Foundation.
+ */
+
+#include <linux/version.h>
+#include <linux/config.h>
+#include <linux/kernel.h>
+#include <linux/init.h>
+#include <linux/module.h>
+#include <linux/dyn-tick.h>
+#include <linux/timer.h>
+#include <linux/irq.h>
+#include <asm/apic.h>
+#include <asm/dyn-tick.h>
+
+/* Fixme: Disable NMI Watchdog */
+static void apic_reprogram(unsigned long jif_next)
+{
+	reprogram_apic_timer(jif_next - jiffies);
+}
+
+static void pit_reprogram(unsigned long jif_next)
+{
+	reprogram_pit_timer(jif_next - jiffies);
+}
+
+static void arch_all_cpus_idle(int how_long)
+{
+	if (cpu_has_local_apic())
+		disable_pit_timer();
+}
+
+static int arch_enable(void)
+{
+	return 0;
+}
+
+static int arch_disable(void)
+{
+	return 0;
+}
+
+static struct dyn_tick_timer arch_dyn_tick = {
+	.arch_reprogram		= &pit_reprogram,
+	.arch_all_cpus_idle	= &arch_all_cpus_idle,
+	.arch_enable		= &arch_enable,
+	.arch_disable		= &arch_disable,
+	.min_skip		= DYN_TICK_MIN_SKIP,
+	.state			= 0,
+};
+
+struct dyn_tick_timer *dyn_tick = &arch_dyn_tick;
+
+int __init dyn_tick_arch_init(void)
+{
+	if (!cpu_has_local_apic())
+		set_dyn_tick_limits(0xffff / LATCH, 0);
+
+	printk(KERN_INFO "dyn-tick: Maximum ticks to skip limited to %i\n",
+		dyn_tick->max_skip);
+
+	return 0;
+}
+
+static int __init dyn_tick_init(void)
+{
+	dyn_tick->arch_init = dyn_tick_arch_init;
+	dyn_tick_register(&arch_dyn_tick);
+
+	return 0;
+}
+
+arch_initcall(dyn_tick_init);
+
+/* Functions that need blank prototypes for !CONFIG_NO_IDLE_HZ below here */
+int __init setup_dyn_tick_use_apic(unsigned int calibration_result)
+{
+	if (calibration_result) {
+		dyn_tick->arch_reprogram = &apic_reprogram;
+		dyn_tick->state |= DYN_TICK_APICABLE;
+		return 1;
+	}
+	dyn_tick->state &= ~DYN_TICK_APICABLE;
+	printk(KERN_INFO "dyn-tick: Cannot use local APIC\n");
+	return 0;
+}
+
+void dyn_tick_interrupt(struct pt_regs *regs)
+{
+	int cpu = smp_processor_id();
+
+	if (!cpu_isset(cpu, nohz_cpu_mask))
+		return;
+
+	spin_lock(&dyn_tick->lock);
+	if (cpus_equal(nohz_cpu_mask, cpu_online_map)) {
+		/* All were sleeping, recover jiffies */
+		int lost = cur_timer->mark_offset();
+		if (lost && in_irq())
+			do_timer(regs);
+		if (cpu_has_local_apic())
+			enable_pit_timer();
+	}
+	cpu_clear(cpu, nohz_cpu_mask);
+	spin_unlock(&dyn_tick->lock);
+
+	/* Make sure we don't miss the next timer tick */
+	dyn_early_reprogram(1);
+
+	conditional_run_local_timers();
+	/* Fixme: Enable NMI watchdog */
+}
+
+
+void __init dyn_tick_time_init(struct timer_opts *cur_timer)
+{
+	spin_lock_init(&dyn_tick->lock);
+
+	if (strncmp(cur_timer->name, "pmtmr", 3) == 0) {
+		dyn_tick->state |= DYN_TICK_SUITABLE;
+		printk(KERN_INFO "dyn-tick: Found suitable timer: %s\n",
+		       cur_timer->name);
+	} else
+		printk(KERN_ERR "dyn-tick: Cannot use timer %s\n",
+		       cur_timer->name);
+}
+
+inline void idle_reprogram_timer(void)
+{
+	local_irq_disable();
+	if (!need_resched())
+		timer_dyn_reprogram();
+	local_irq_enable();
+}
Index: linux-2.6.15-rc5-dt/arch/i386/kernel/io_apic.c
===================================================================
--- linux-2.6.15-rc5-dt.orig/arch/i386/kernel/io_apic.c
+++ linux-2.6.15-rc5-dt/arch/i386/kernel/io_apic.c
@@ -32,6 +32,7 @@
 #include <linux/acpi.h>
 #include <linux/module.h>
 #include <linux/sysdev.h>
+#include <linux/dyn-tick.h>
 
 #include <asm/io.h>
 #include <asm/smp.h>
@@ -1179,6 +1180,7 @@ next:
 
 static struct hw_interrupt_type ioapic_level_type;
 static struct hw_interrupt_type ioapic_edge_type;
+static struct hw_interrupt_type ioapic_edge_type_irq0;
 
 #define IOAPIC_AUTO	-1
 #define IOAPIC_EDGE	0
@@ -1190,15 +1192,19 @@ static inline void ioapic_register_intr(
 		if ((trigger == IOAPIC_AUTO && IO_APIC_irq_trigger(irq)) ||
 				trigger == IOAPIC_LEVEL)
 			irq_desc[vector].handler = &ioapic_level_type;
-		else
+		else if (vector)
 			irq_desc[vector].handler = &ioapic_edge_type;
+		else
+			irq_desc[vector].handler = &ioapic_edge_type_irq0;
 		set_intr_gate(vector, interrupt[vector]);
 	} else	{
 		if ((trigger == IOAPIC_AUTO && IO_APIC_irq_trigger(irq)) ||
 				trigger == IOAPIC_LEVEL)
 			irq_desc[irq].handler = &ioapic_level_type;
-		else
+		else if (irq)
 			irq_desc[irq].handler = &ioapic_edge_type;
+		else
+			irq_desc[irq].handler = &ioapic_edge_type_irq0;
 		set_intr_gate(vector, interrupt[irq]);
 	}
 }
@@ -1311,7 +1317,7 @@ static void __init setup_ExtINT_IRQ0_pin
 	 * The timer IRQ doesn't have to know that behind the
 	 * scene we have a 8259A-master in AEOI mode ...
 	 */
-	irq_desc[0].handler = &ioapic_edge_type;
+	irq_desc[0].handler = &ioapic_edge_type_irq0;
 
 	/*
 	 * Add it to the IO-APIC irq-routing table:
@@ -2088,6 +2094,20 @@ static struct hw_interrupt_type ioapic_l
 #endif
 };
 
+/* Needed to disable PIT interrupts when all CPUs sleep */
+static struct hw_interrupt_type ioapic_edge_type_irq0 __read_mostly = {
+	.typename 	= "IO-APIC-edge-irq0",
+	.startup 	= startup_edge_ioapic,
+	.shutdown 	= shutdown_edge_ioapic,
+	.enable 	= unmask_IO_APIC_irq,
+	.disable 	= mask_IO_APIC_irq,
+	.ack 		= ack_edge_ioapic,
+	.end 		= end_edge_ioapic,
+#ifdef CONFIG_SMP
+	.set_affinity 	= set_ioapic_affinity,
+#endif
+};
+
 static inline void init_IO_APIC_traps(void)
 {
 	int irq;
Index: linux-2.6.15-rc5-dt/arch/i386/kernel/irq.c
===================================================================
--- linux-2.6.15-rc5-dt.orig/arch/i386/kernel/irq.c
+++ linux-2.6.15-rc5-dt/arch/i386/kernel/irq.c
@@ -18,6 +18,8 @@
 #include <linux/notifier.h>
 #include <linux/cpu.h>
 #include <linux/delay.h>
+#include <linux/dyn-tick.h>
+#include <asm/dyn-tick.h>
 
 DEFINE_PER_CPU(irq_cpustat_t, irq_stat) ____cacheline_maxaligned_in_smp;
 EXPORT_PER_CPU_SYMBOL(irq_stat);
@@ -76,6 +78,8 @@ fastcall unsigned int do_IRQ(struct pt_r
 	}
 #endif
 
+	dyn_tick_interrupt(regs);
+
 #ifdef CONFIG_4KSTACKS
 
 	curctx = (union irq_ctx *) current_thread_info();
Index: linux-2.6.15-rc5-dt/arch/i386/kernel/Makefile
===================================================================
--- linux-2.6.15-rc5-dt.orig/arch/i386/kernel/Makefile
+++ linux-2.6.15-rc5-dt/arch/i386/kernel/Makefile
@@ -32,6 +32,7 @@ obj-$(CONFIG_MODULES)		+= module.o
 obj-y				+= sysenter.o vsyscall.o
 obj-$(CONFIG_ACPI_SRAT) 	+= srat.o
 obj-$(CONFIG_HPET_TIMER) 	+= time_hpet.o
+obj-$(CONFIG_NO_IDLE_HZ) 	+= dyn-tick.o
 obj-$(CONFIG_EFI) 		+= efi.o efi_stub.o
 obj-$(CONFIG_EARLY_PRINTK)	+= early_printk.o
 
Index: linux-2.6.15-rc5-dt/arch/i386/kernel/process.c
===================================================================
--- linux-2.6.15-rc5-dt.orig/arch/i386/kernel/process.c
+++ linux-2.6.15-rc5-dt/arch/i386/kernel/process.c
@@ -39,6 +39,7 @@
 #include <linux/ptrace.h>
 #include <linux/random.h>
 #include <linux/kprobes.h>
+#include <linux/dyn-tick.h>
 
 #include <asm/uaccess.h>
 #include <asm/pgtable.h>
@@ -56,6 +57,7 @@
 
 #include <asm/tlbflush.h>
 #include <asm/cpu.h>
+#include <asm/dyn-tick.h>
 
 asmlinkage void ret_from_fork(void) __asm__("ret_from_fork");
 
@@ -193,6 +195,8 @@ void cpu_idle(void)
 			if (cpu_is_offline(cpu))
 				play_dead();
 
+			idle_reprogram_timer();
+
 			__get_cpu_var(irq_stat).idle_timestamp = jiffies;
 			idle();
 		}
Index: linux-2.6.15-rc5-dt/arch/i386/kernel/smp.c
===================================================================
--- linux-2.6.15-rc5-dt.orig/arch/i386/kernel/smp.c
+++ linux-2.6.15-rc5-dt/arch/i386/kernel/smp.c
@@ -20,9 +20,11 @@
 #include <linux/interrupt.h>
 #include <linux/cpu.h>
 #include <linux/module.h>
+#include <linux/dyn-tick.h>
 
 #include <asm/mtrr.h>
 #include <asm/tlbflush.h>
+#include <asm/dyn-tick.h>
 #include <mach_apic.h>
 
 /*
@@ -313,6 +315,8 @@ fastcall void smp_invalidate_interrupt(s
 {
 	unsigned long cpu;
 
+	dyn_tick_interrupt(regs);
+
 	cpu = get_cpu();
 
 	if (!cpu_isset(cpu, flush_cpumask))
@@ -600,6 +604,8 @@ void smp_send_stop(void)
 fastcall void smp_reschedule_interrupt(struct pt_regs *regs)
 {
 	ack_APIC_irq();
+
+	dyn_tick_interrupt(regs);
 }
 
 fastcall void smp_call_function_interrupt(struct pt_regs *regs)
@@ -609,6 +615,9 @@ fastcall void smp_call_function_interrup
 	int wait = call_data->wait;
 
 	ack_APIC_irq();
+
+	dyn_tick_interrupt(regs);
+
 	/*
 	 * Notify initiating CPU that I've grabbed the data and am
 	 * about to execute the function
Index: linux-2.6.15-rc5-dt/arch/i386/kernel/time.c
===================================================================
--- linux-2.6.15-rc5-dt.orig/arch/i386/kernel/time.c
+++ linux-2.6.15-rc5-dt/arch/i386/kernel/time.c
@@ -46,6 +46,7 @@
 #include <linux/bcd.h>
 #include <linux/efi.h>
 #include <linux/mca.h>
+#include <linux/dyn-tick.h>
 
 #include <asm/io.h>
 #include <asm/smp.h>
@@ -56,6 +57,7 @@
 #include <asm/uaccess.h>
 #include <asm/processor.h>
 #include <asm/timer.h>
+#include <asm/dyn-tick.h>
 
 #include "mach_time.h"
 
@@ -245,7 +247,7 @@ EXPORT_SYMBOL(profile_pc);
  * timer_interrupt() needs to keep up the real-time clock,
  * as well as call the "do_timer()" routine every clocktick
  */
-static inline void do_timer_interrupt(int irq, struct pt_regs *regs)
+static inline void do_timer_interrupt(int irq, struct pt_regs *regs, int lost)
 {
 #ifdef CONFIG_X86_IO_APIC
 	if (timer_ack) {
@@ -263,7 +265,8 @@ static inline void do_timer_interrupt(in
 	}
 #endif
 
-	do_timer_interrupt_hook(regs);
+	if (!dyn_tick_enabled() || lost)
+		do_timer_interrupt_hook(regs);
 
 
 	if (MCA_bus) {
@@ -288,6 +291,8 @@ static inline void do_timer_interrupt(in
  */
 irqreturn_t timer_interrupt(int irq, void *dev_id, struct pt_regs *regs)
 {
+	int lost;
+
 	/*
 	 * Here we are in the timer irq handler. We just have irqs locally
 	 * disabled but we don't know if the timer_bh is running on the other
@@ -297,9 +302,9 @@ irqreturn_t timer_interrupt(int irq, voi
 	 */
 	write_seqlock(&xtime_lock);
 
-	cur_timer->mark_offset();
- 
-	do_timer_interrupt(irq, regs);
+	lost = cur_timer->mark_offset();
+
+	do_timer_interrupt(irq, regs, lost);
 
 	write_sequnlock(&xtime_lock);
 	return IRQ_HANDLED;
@@ -425,7 +430,7 @@ static struct sysdev_class timer_sysclas
 
 
 /* XXX this driverfs stuff should probably go elsewhere later -john */
-static struct sys_device device_timer = {
+struct sys_device device_timer = {
 	.id	= 0,
 	.cls	= &timer_sysclass,
 };
@@ -481,5 +486,7 @@ void __init time_init(void)
 	cur_timer = select_timer();
 	printk(KERN_INFO "Using %s for high-res timesource\n",cur_timer->name);
 
+	dyn_tick_time_init(cur_timer);
+
 	time_init_hook();
 }
Index: linux-2.6.15-rc5-dt/arch/i386/kernel/timers/timer_pit.c
===================================================================
--- linux-2.6.15-rc5-dt.orig/arch/i386/kernel/timers/timer_pit.c
+++ linux-2.6.15-rc5-dt/arch/i386/kernel/timers/timer_pit.c
@@ -32,9 +32,10 @@ static int __init init_pit(char* overrid
 	return 0;
 }
 
-static void mark_offset_pit(void)
+static int mark_offset_pit(void)
 {
 	/* nothing needed */
+	return 1;
 }
 
 static unsigned long long monotonic_clock_pit(void)
@@ -148,6 +149,38 @@ static unsigned long get_offset_pit(void
 	return count;
 }
 
+void disable_pit_timer(void)
+{
+	irq_desc[0].handler->disable(0);
+}
+
+void enable_pit_timer(void)
+{
+	irq_desc[0].handler->enable(0);
+}
+
+/*
+ * Reprograms the next timer interrupt
+ * PIT timer reprogramming code taken from APM code.
+ * Note that PIT timer is a 16-bit timer, which allows max
+ * skip of only few seconds.
+ */
+void reprogram_pit_timer(unsigned long jiffies_to_skip)
+{
+	int skip;
+	extern spinlock_t i8253_lock;
+	unsigned long flags;
+
+	skip = jiffies_to_skip * LATCH;
+	if (skip > 0xffff)
+		skip = 0xffff;
+
+	spin_lock_irqsave(&i8253_lock, flags);
+	outb_p(0x34, PIT_MODE);		/* binary, mode 2, LSB/MSB, ch 0 */
+	outb_p(skip & 0xff, PIT_CH0);	/* LSB */
+	outb(skip >> 8, PIT_CH0);	/* MSB */
+	spin_unlock_irqrestore(&i8253_lock, flags);
+}
 
 /* tsc timer_opts struct */
 struct timer_opts timer_pit = {
Index: linux-2.6.15-rc5-dt/arch/i386/kernel/timers/timer_pm.c
===================================================================
--- linux-2.6.15-rc5-dt.orig/arch/i386/kernel/timers/timer_pm.c
+++ linux-2.6.15-rc5-dt/arch/i386/kernel/timers/timer_pm.c
@@ -15,6 +15,7 @@
 #include <linux/module.h>
 #include <linux/device.h>
 #include <linux/init.h>
+#include <linux/dyn-tick.h>
 #include <asm/types.h>
 #include <asm/timer.h>
 #include <asm/smp.h>
@@ -28,7 +29,7 @@
 #define PMTMR_TICKS_PER_SEC 3579545
 #define PMTMR_EXPECTED_RATE \
   ((CALIBRATE_LATCH * (PMTMR_TICKS_PER_SEC >> 10)) / (CLOCK_TICK_RATE>>10))
-
+#define PMTMR_TICKS_PER_JIFFY (PMTMR_EXPECTED_RATE / (CALIBRATE_LATCH/LATCH))
 
 /* The I/O port the PMTMR resides at.
  * The location is detected during setup_arch(),
@@ -127,7 +128,13 @@ pm_good:
 	if (verify_pmtmr_rate() != 0)
 		return -ENODEV;
 
+	printk("Using %u PM timer ticks per jiffy \n", PMTMR_TICKS_PER_JIFFY);
+
+	offset_tick = read_pmtmr();
+	setup_pit_timer();
+
 	init_cpu_khz();
+	set_dyn_tick_limits(((0xFFFFFF / 1000000) * 286 * HZ) >> 10, 0);
 	return 0;
 }
 
@@ -148,10 +155,9 @@ static inline u32 cyc2us(u32 cycles)
  * this gets called during each timer interrupt
  *   - Called while holding the writer xtime_lock
  */
-static void mark_offset_pmtmr(void)
+static int mark_offset_pmtmr(void)
 {
 	u32 lost, delta, last_offset;
-	static int first_run = 1;
 	last_offset = offset_tick;
 
 	write_seqlock(&monotonic_lock);
@@ -161,29 +167,20 @@ static void mark_offset_pmtmr(void)
 	/* calculate tick interval */
 	delta = (offset_tick - last_offset) & ACPI_PM_MASK;
 
-	/* convert to usecs */
-	delta = cyc2us(delta);
-
 	/* update the monotonic base value */
-	monotonic_base += delta * NSEC_PER_USEC;
+	monotonic_base += cyc2us(delta) * NSEC_PER_USEC;
 	write_sequnlock(&monotonic_lock);
 
 	/* convert to ticks */
 	delta += offset_delay;
-	lost = delta / (USEC_PER_SEC / HZ);
-	offset_delay = delta % (USEC_PER_SEC / HZ);
-
+	lost = delta / PMTMR_TICKS_PER_JIFFY;
+	offset_delay = delta % PMTMR_TICKS_PER_JIFFY;
 
 	/* compensate for lost ticks */
 	if (lost >= 2)
 		jiffies_64 += lost - 1;
 
-	/* don't calculate delay for first run,
-	   or if we've got less then a tick */
-	if (first_run || (lost < 1)) {
-		first_run = 0;
-		offset_delay = 0;
-	}
+	return lost;
 }
 
 static int pmtmr_resume(void)
@@ -192,6 +189,7 @@ static int pmtmr_resume(void)
 	/* Assume this is the last mark offset time */
 	offset_tick = read_pmtmr();
 	write_sequnlock(&monotonic_lock);
+	offset_delay = 0;
 	return 0;
 }
 
@@ -243,7 +241,7 @@ static unsigned long get_offset_pmtmr(vo
 	now = read_pmtmr();
 	delta = (now - offset)&ACPI_PM_MASK;
 
-	return (unsigned long) offset_delay + cyc2us(delta);
+	return (unsigned long) cyc2us(delta + offset_delay);
 }
 
 
Index: linux-2.6.15-rc5-dt/arch/i386/kernel/timers/timer_tsc.c
===================================================================
--- linux-2.6.15-rc5-dt.orig/arch/i386/kernel/timers/timer_tsc.c
+++ linux-2.6.15-rc5-dt/arch/i386/kernel/timers/timer_tsc.c
@@ -14,6 +14,7 @@
 #include <linux/cpufreq.h>
 #include <linux/string.h>
 #include <linux/jiffies.h>
+#include <linux/dyn-tick.h>
 
 #include <asm/timer.h>
 #include <asm/io.h>
@@ -32,8 +33,6 @@ static unsigned long hpet_last;
 static struct timer_opts timer_tsc;
 #endif
 
-static inline void cpufreq_delayed_get(void);
-
 int tsc_disable __devinitdata = 0;
 
 static int use_tsc;
@@ -171,11 +170,21 @@ static void delay_tsc(unsigned long loop
 	} while ((now-bclock) < loops);
 }
 
+/* update the monotonic base value */
+static inline void update_monotonic_base(unsigned long long last_offset)
+{
+	unsigned long long this_offset;
+
+	this_offset = ((unsigned long long)last_tsc_high << 32) | last_tsc_low;
+	monotonic_base += cycles_2_ns(this_offset - last_offset);
+}
+
 #ifdef CONFIG_HPET_TIMER
-static void mark_offset_tsc_hpet(void)
+static int mark_offset_tsc_hpet(void)
 {
-	unsigned long long this_offset, last_offset;
+	unsigned long long last_offset;
  	unsigned long offset, temp, hpet_current;
+ 	int lost_ticks = 0;
 
 	write_seqlock(&monotonic_lock);
 	last_offset = ((unsigned long long)last_tsc_high<<32)|last_tsc_low;
@@ -197,14 +206,12 @@ static void mark_offset_tsc_hpet(void)
 	/* lost tick compensation */
 	offset = hpet_readl(HPET_T0_CMP) - hpet_tick;
 	if (unlikely(((offset - hpet_last) > hpet_tick) && (hpet_last != 0))) {
-		int lost_ticks = (offset - hpet_last) / hpet_tick;
+		lost_ticks = (offset - hpet_last) / hpet_tick;
 		jiffies_64 += lost_ticks;
 	}
 	hpet_last = hpet_current;
 
-	/* update the monotonic base value */
-	this_offset = ((unsigned long long)last_tsc_high<<32)|last_tsc_low;
-	monotonic_base += cycles_2_ns(this_offset - last_offset);
+	update_monotonic_base(last_offset);
 	write_sequnlock(&monotonic_lock);
 
 	/* calculate delay_at_last_interrupt */
@@ -218,6 +225,8 @@ static void mark_offset_tsc_hpet(void)
 	delay_at_last_interrupt = hpet_current - offset;
 	ASM_MUL64_REG(temp, delay_at_last_interrupt,
 			hpet_usec_quotient, delay_at_last_interrupt);
+
+	return lost_ticks;
 }
 #endif
 
@@ -242,7 +251,7 @@ static void handle_cpufreq_delayed_get(v
  * to verify the CPU frequency the timing core thinks the CPU is running
  * at is still correct.
  */
-static inline void cpufreq_delayed_get(void) 
+void cpufreq_delayed_get(void)
 {
 	if (cpufreq_init && !cpufreq_delayed_issched) {
 		cpufreq_delayed_issched = 1;
@@ -321,7 +330,7 @@ static int __init cpufreq_tsc(void)
 core_initcall(cpufreq_tsc);
 
 #else /* CONFIG_CPU_FREQ */
-static inline void cpufreq_delayed_get(void) { return; }
+void cpufreq_delayed_get(void) { return; }
 #endif 
 
 int recalibrate_cpu_khz(void)
@@ -344,15 +353,14 @@ int recalibrate_cpu_khz(void)
 }
 EXPORT_SYMBOL(recalibrate_cpu_khz);
 
-static void mark_offset_tsc(void)
+static int mark_offset_tsc(void)
 {
 	unsigned long lost,delay;
 	unsigned long delta = last_tsc_low;
 	int count;
 	int countmp;
 	static int count1 = 0;
-	unsigned long long this_offset, last_offset;
-	static int lost_count = 0;
+	unsigned long long last_offset;
 
 	write_seqlock(&monotonic_lock);
 	last_offset = ((unsigned long long)last_tsc_high<<32)|last_tsc_low;
@@ -419,29 +427,9 @@ static void mark_offset_tsc(void)
 	delta += delay_at_last_interrupt;
 	lost = delta/(1000000/HZ);
 	delay = delta%(1000000/HZ);
-	if (lost >= 2) {
-		jiffies_64 += lost-1;
+	tsc_sanity_check(lost);
 
-		/* sanity check to ensure we're not always losing ticks */
-		if (lost_count++ > 100) {
-			printk(KERN_WARNING "Losing too many ticks!\n");
-			printk(KERN_WARNING "TSC cannot be used as a timesource.  \n");
-			printk(KERN_WARNING "Possible reasons for this are:\n");
-			printk(KERN_WARNING "  You're running with Speedstep,\n");
-			printk(KERN_WARNING "  You don't have DMA enabled for your hard disk (see hdparm),\n");
-			printk(KERN_WARNING "  Incorrect TSC synchronization on an SMP system (see dmesg).\n");
-			printk(KERN_WARNING "Falling back to a sane timesource now.\n");
-
-			clock_fallback();
-		}
-		/* ... but give the TSC a fair chance */
-		if (lost_count > 25)
-			cpufreq_delayed_get();
-	} else
-		lost_count = 0;
-	/* update the monotonic base value */
-	this_offset = ((unsigned long long)last_tsc_high<<32)|last_tsc_low;
-	monotonic_base += cycles_2_ns(this_offset - last_offset);
+	update_monotonic_base(last_offset);
 	write_sequnlock(&monotonic_lock);
 
 	/* calculate delay_at_last_interrupt */
@@ -454,6 +442,8 @@ static void mark_offset_tsc(void)
 	 */
 	if (lost && abs(delay - delay_at_last_interrupt) > (900000/HZ))
 		jiffies_64++;
+
+	return lost;
 }
 
 static int __init init_tsc(char* override)
@@ -542,6 +532,8 @@ static int __init init_tsc(char* overrid
 					cpu_khz / 1000, cpu_khz % 1000);
 			}
 			set_cyc2ns_scale(cpu_khz);
+			set_dyn_tick_limits((0xFFFFFFFF / (cpu_khz * 1000)) *
+				HZ, 0);
 			return 0;
 		}
 	}
Index: linux-2.6.15-rc5-dt/include/asm-i386/apic.h
===================================================================
--- linux-2.6.15-rc5-dt.orig/include/asm-i386/apic.h
+++ linux-2.6.15-rc5-dt/include/asm-i386/apic.h
@@ -121,6 +121,7 @@ extern void nmi_watchdog_tick (struct pt
 extern int APIC_init_uniprocessor (void);
 extern void disable_APIC_timer(void);
 extern void enable_APIC_timer(void);
+extern void reprogram_apic_timer(unsigned long count);
 
 extern void enable_NMI_through_LVT0 (void * dummy);
 
@@ -134,6 +135,7 @@ extern int disable_timer_pin_1;
 
 #else /* !CONFIG_X86_LOCAL_APIC */
 static inline void lapic_shutdown(void) { }
+static inline void reprogram_apic_timer(unsigned long count) { }
 
 #endif /* !CONFIG_X86_LOCAL_APIC */
 
Index: linux-2.6.15-rc5-dt/include/asm-i386/dyn-tick.h
===================================================================
--- /dev/null
+++ linux-2.6.15-rc5-dt/include/asm-i386/dyn-tick.h
@@ -0,0 +1,65 @@
+/*
+ * linux/include/asm-i386/dyn-tick.h
+ *
+ * Copyright (C) 2004 Nokia Corporation
+ * Written by Tony Lindgen <[email protected]> and
+ * Tuukka Tikkanen <[email protected]>
+ * Rewritten by Con Kolivas <[email protected]>
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2 as
+ * published by the Free Software Foundation.
+ */
+
+#ifndef _ASM_I386_DYN_TICK_H_
+#define _ASM_I386_DYN_TICK_H_
+
+#include <asm/apic.h>
+#include <asm/timer.h>
+
+#ifdef CONFIG_NO_IDLE_HZ
+extern void idle_reprogram_timer(void);
+extern void dyn_tick_interrupt(struct pt_regs *regs);
+extern int __init setup_dyn_tick_use_apic(unsigned int calibration_result);
+extern void __init dyn_tick_time_init(struct timer_opts *cur_timer);
+
+/*
+ * Needs to be different to the arch independant values specified in
+ * include/linux/dyn-tick.h to share the dyn_tick_timer.state struct
+ * member.
+ */
+#define DYN_TICK_APICABLE	(1 << 3)
+
+#if (defined(CONFIG_SMP) || defined(CONFIG_X86_UP_APIC))
+static inline int cpu_has_local_apic(void)
+{
+	return (dyn_tick->state & DYN_TICK_APICABLE);
+}
+
+#else	/* (defined(CONFIG_SMP) || defined(CONFIG_X86_UP_APIC)) */
+static inline int cpu_has_local_apic(void)
+{
+	return 0;
+}
+#endif	/* (defined(CONFIG_SMP) || defined(CONFIG_X86_UP_APIC)) */
+
+#else	/* CONFIG_NO_IDLE_HZ */
+static inline void idle_reprogram_timer(void)
+{
+}
+
+static inline void dyn_tick_interrupt(struct pt_regs *regs)
+{
+}
+
+static inline int setup_dyn_tick_use_apic(unsigned int calibration_result)
+{
+	return 0;
+}
+
+static inline void dyn_tick_time_init(struct timer_opts *cur_timer)
+{
+}
+#endif	/* CONFIG_NO_IDLE_HZ */
+
+#endif /* _ASM_I386_DYN_TICK_H_ */
Index: linux-2.6.15-rc5-dt/include/asm-i386/timer.h
===================================================================
--- linux-2.6.15-rc5-dt.orig/include/asm-i386/timer.h
+++ linux-2.6.15-rc5-dt/include/asm-i386/timer.h
@@ -1,5 +1,6 @@
 #ifndef _ASMi386_TIMER_H
 #define _ASMi386_TIMER_H
+#include <linux/jiffies.h>
 #include <linux/init.h>
 #include <linux/pm.h>
 
@@ -19,7 +20,7 @@
  */
 struct timer_opts {
 	char* name;
-	void (*mark_offset)(void);
+	int (*mark_offset)(void);
 	unsigned long (*get_offset)(void);
 	unsigned long long (*monotonic_clock)(void);
 	void (*delay)(unsigned long);
@@ -38,6 +39,9 @@ struct init_timer_opts {
 extern struct timer_opts* __init select_timer(void);
 extern void clock_fallback(void);
 void setup_pit_timer(void);
+extern void disable_pit_timer(void);
+extern void enable_pit_timer(void);
+extern void reprogram_pit_timer(unsigned long jiffies_to_skip);
 
 /* Modifiers for buggy PIT handling */
 
@@ -67,4 +71,41 @@ extern unsigned long calibrate_tsc_hpet(
 #ifdef CONFIG_X86_PM_TIMER
 extern struct init_timer_opts timer_pmtmr_init;
 #endif
+#ifdef CONFIG_NO_IDLE_HZ
+static inline void tsc_sanity_check(int lost)
+{
+}
+#else /* CONFIG_NO_IDLE_HZ */
+extern void cpufreq_delayed_get(void);
+
+static inline void tsc_sanity_check(int lost)
+{
+	static int lost_count = 0;
+
+	if (lost >= 2) {
+		jiffies_64 += lost-1;
+
+		/* sanity check to ensure we're not always losing ticks */
+		if (lost_count++ > 100) {
+			printk(KERN_WARNING "Losing too many ticks!\n");
+			printk(KERN_WARNING "TSC cannot be used as a timesource.  \n");
+			printk(KERN_WARNING "Possible reasons for this are:\n");
+			printk(KERN_WARNING "  You're running with Speedstep,\n");
+			printk(KERN_WARNING "  You don't have DMA enabled for your hard disk (see hdparm),\n");
+			printk(KERN_WARNING "  Incorrect TSC synchronization on an SMP system (see dmesg).\n");
+			printk(KERN_WARNING "Falling back to a sane timesource now.\n");
+
+			clock_fallback();
+		}
+		/* ... but give the TSC a fair chance */
+		if (lost_count > 25)
+			cpufreq_delayed_get();
+	} else
+		lost_count = 0;
+}
+
+static inline void dyn_tick_time_init(struct timer_opts *cur_timer)
+{
+}
+#endif /* CONFIG_NO_IDLE_HZ */
 #endif
Index: linux-2.6.15-rc5-dt/arch/i386/kernel/timers/timer_cyclone.c
===================================================================
--- linux-2.6.15-rc5-dt.orig/arch/i386/kernel/timers/timer_cyclone.c
+++ linux-2.6.15-rc5-dt/arch/i386/kernel/timers/timer_cyclone.c
@@ -45,7 +45,7 @@ static seqlock_t monotonic_lock = SEQLOC
 	} while (high != cyclone_timer[1]);
 
 
-static void mark_offset_cyclone(void)
+static int mark_offset_cyclone(void)
 {
 	unsigned long lost, delay;
 	unsigned long delta = last_cyclone_low;
@@ -101,6 +101,8 @@ static void mark_offset_cyclone(void)
 	 */
 	if (lost && abs(delay - delay_at_last_interrupt) > (900000/HZ))
 		jiffies_64++;
+
+	return lost;
 }
 
 static unsigned long get_offset_cyclone(void)
Index: linux-2.6.15-rc5-dt/arch/i386/kernel/timers/timer_hpet.c
===================================================================
--- linux-2.6.15-rc5-dt.orig/arch/i386/kernel/timers/timer_hpet.c
+++ linux-2.6.15-rc5-dt/arch/i386/kernel/timers/timer_hpet.c
@@ -101,7 +101,7 @@ static unsigned long get_offset_hpet(voi
 	return edx;
 }
 
-static void mark_offset_hpet(void)
+static int mark_offset_hpet(void)
 {
 	unsigned long long this_offset, last_offset;
 	unsigned long offset;
@@ -124,6 +124,8 @@ static void mark_offset_hpet(void)
 	this_offset = ((unsigned long long)last_tsc_high<<32)|last_tsc_low;
 	monotonic_base += cycles_2_ns(this_offset - last_offset);
 	write_sequnlock(&monotonic_lock);
+
+	return 1;
 }
 
 static void delay_hpet(unsigned long loops)
Index: linux-2.6.15-rc5-dt/arch/i386/kernel/timers/timer_none.c
===================================================================
--- linux-2.6.15-rc5-dt.orig/arch/i386/kernel/timers/timer_none.c
+++ linux-2.6.15-rc5-dt/arch/i386/kernel/timers/timer_none.c
@@ -1,9 +1,10 @@
 #include <linux/init.h>
 #include <asm/timer.h>
 
-static void mark_offset_none(void)
+static int mark_offset_none(void)
 {
 	/* nothing needed */
+	return 1;
 }
 
 static unsigned long get_offset_none(void)
Index: linux-2.6.15-rc5-dt/drivers/acpi/processor_idle.c
===================================================================
--- linux-2.6.15-rc5-dt.orig/drivers/acpi/processor_idle.c
+++ linux-2.6.15-rc5-dt/drivers/acpi/processor_idle.c
@@ -38,6 +38,7 @@
 #include <linux/dmi.h>
 #include <linux/moduleparam.h>
 #include <linux/sched.h>	/* need_resched() */
+#include <linux/dyn-tick.h>
 
 #include <asm/io.h>
 #include <asm/uaccess.h>
@@ -60,6 +61,7 @@ module_param(max_cstate, uint, 0644);
 static unsigned int nocst = 0;
 module_param(nocst, uint, 0000);
 
+#define BM_RELAX	(msecs_to_jiffies(32))	/* Time to calm down */
 /*
  * bm_history -- bit-mask with a bit per jiffy of bus-master activity
  * 1000 HZ: 0xFFFFFFFF: 32 jiffies = 32ms
@@ -178,6 +180,17 @@ static void acpi_safe_halt(void)
 
 static atomic_t c3_cpu_count;
 
+static inline int skipped_since_bm_check(void)
+{
+	/*
+	 * If we've been skipping ticks in the last few ticks there wouldn't be
+	 * any busmaster activity.
+	 */
+	if (dyn_tick->last_skip + dyn_tick->skip >= jiffies)
+		return dyn_tick->skip;
+	return 0;
+}
+
 static void acpi_processor_idle(void)
 {
 	struct acpi_processor *pr = NULL;
@@ -223,6 +236,18 @@ static void acpi_processor_idle(void)
 	if (pr->flags.bm_check) {
 		u32 bm_status = 0;
 		unsigned long diff = jiffies - pr->power.bm_check_timestamp;
+		int skipped = 0;
+
+		if (dyn_tick_enabled()) {
+			skipped = skipped_since_bm_check();
+			if (skipped) {
+				diff = 0;
+				do {
+					if (!(pr->power.bm_activity >>= 1))
+						break;
+				} while (skipped--);
+			}
+		}
 
 		if (diff > 32)
 			diff = 32;
@@ -238,7 +263,8 @@ static void acpi_processor_idle(void)
 		acpi_get_register(ACPI_BITREG_BUS_MASTER_STATUS,
 				  &bm_status, ACPI_MTX_DO_NOT_LOCK);
 		if (bm_status) {
-			pr->power.bm_activity++;
+			if (skipped < BM_RELAX)
+				pr->power.bm_activity++;
 			acpi_set_register(ACPI_BITREG_BUS_MASTER_STATUS,
 					  1, ACPI_MTX_DO_NOT_LOCK);
 		}
Index: linux-2.6.15-rc5-dt/kernel/timer_top.c
===================================================================
--- /dev/null
+++ linux-2.6.15-rc5-dt/kernel/timer_top.c
@@ -0,0 +1,237 @@
+/*
+ * kernel/timer_top.c
+ *
+ * Export Timers information to /proc/timer_info
+ *
+ * Copyright (C) 2005 Instituto Nokia de Tecnologia - INdT - Manaus
+ * Written by Daniel Petrini <[email protected]>
+ *
+ * This utility should be used to get information from the system timers
+ * and maybe optimize the system once you know which timers are being used
+ * and the process which starts them.
+ * This is particular useful above dynamic tick implementation. One can
+ * see who is starting timers and make the HZ value increase.
+ *
+ * We export the addresses and counting of timer functions being called,
+ * the pid and cmdline from the owner process if applicable.
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2 as
+ * published by the Free Software Foundation.
+ */
+
+
+#include <linux/list.h>
+#include <linux/proc_fs.h>
+#include <linux/module.h>
+#include <linux/spinlock.h>
+#include <linux/sched.h>
+#include <linux/seq_file.h>
+#include <asm/uaccess.h>
+
+#define VERSION		"Timer Top v0.9.7"
+
+struct timer_top_info {
+	unsigned int		func_pointer;
+	unsigned long		counter;
+	pid_t			pid;
+	char 			comm[TASK_COMM_LEN];
+	struct list_head 	list;
+};
+
+struct timer_top_root {
+	spinlock_t		lock;
+	struct list_head	list;
+	kmem_cache_t		*cache;
+};
+
+static struct timer_top_root top_root = {
+	.lock		= SPIN_LOCK_UNLOCKED,
+	.list		= LIST_HEAD_INIT(top_root.list),
+};
+
+static struct list_head *timer_list = &top_root.list;
+
+static spinlock_t *top_lock = &top_root.lock;
+static int start_flag = 0; 	/* signs if will collect data or not */
+
+static inline struct timer_top_info *update_top_info(unsigned long function,
+	pid_t pid_info)
+{
+	struct timer_top_info *top;
+
+	list_for_each_entry(top, timer_list, list) {
+		/* if it is in the list increment its count */
+		if (top->func_pointer == function && top->pid == pid_info) {
+			top->counter++;
+			goto out;
+		}
+	}
+
+	top = NULL;
+out:
+	return top;
+}
+
+int account_timer(unsigned long function, unsigned long data)
+{
+	struct timer_top_info *top;
+	struct task_struct * task_info;
+	pid_t pid_info = 0;
+	char name[TASK_COMM_LEN] = "";
+	unsigned long flags;
+
+	if (start_flag == 0)
+		goto out;
+
+	spin_lock_irqsave(top_lock, flags);
+
+	if (data) {
+	       	task_info = (struct task_struct *) data;
+		/* little sanity ... not enough yet */
+		if ((task_info->pid > 0) && (task_info->pid < PID_MAX_LIMIT)) {
+			pid_info = task_info->pid;
+			strncpy(name, task_info->comm, sizeof(task_info->comm));
+		}
+	}
+
+	top = update_top_info(function, pid_info);
+	if (top)
+		goto out_unlock;
+
+	top = kmem_cache_alloc(top_root.cache, GFP_ATOMIC);
+	if (unlikely(!top))
+		goto out_unlock;
+
+	/* if you are here then it didnt find so inserts in the list */
+	top->func_pointer = function;
+	top->counter = 1;
+	top->pid = pid_info;
+	strncpy(top->comm, name, sizeof(name));
+	list_add(&top->list, timer_list);
+
+out_unlock:
+	spin_unlock_irqrestore(top_lock, flags);
+
+out:
+	return 0;
+}
+
+EXPORT_SYMBOL(account_timer);
+
+int timer_list_del(void)
+{
+	struct list_head *aux1, *aux2;
+	struct timer_top_info *entry;
+	unsigned long flags;
+
+	spin_lock_irqsave(top_lock, flags);
+	list_for_each_safe(aux1, aux2, timer_list) {
+		entry = list_entry(aux1, struct timer_top_info, list);
+		list_del(aux1);
+		kmem_cache_free(top_root.cache, entry);
+	}
+	spin_unlock_irqrestore(top_lock, flags);
+	return 0;
+}
+
+/* PROC_FS_SECTION  */
+
+static struct proc_dir_entry *top_info_file;
+static struct proc_dir_entry *top_info_file_out;
+
+/* Statistics output - timer_info*/
+static int proc_read_top_info(struct seq_file *m, void *v)
+{
+	struct timer_top_info *top;
+
+	seq_printf(m, "Function counter - %s\n", VERSION);
+
+	list_for_each_entry(top, timer_list, list) {
+		seq_printf(m, "%x %lu %d %s\n", top->func_pointer, top->counter, top->pid, top->comm);
+	}
+
+	if (start_flag == 0) {
+		seq_printf(m, "Disabled\n");
+	}
+
+	return 0;
+}
+
+static int proc_timertop_open(struct inode *inode, struct file *file)
+{
+	return single_open(file, proc_read_top_info, NULL);
+}
+
+static struct file_operations proc_timertop_operations = {
+	.open		= proc_timertop_open,
+	.read		= seq_read,
+	.llseek		= seq_lseek,
+	.release	= single_release,
+};
+
+#define MAX_INPUT_TOP	10
+
+/* Receive some commands from user - timer_input */
+static int proc_write_timer_input(struct file *file, const char *page,
+                                 unsigned long count, void *data)
+{
+	int len;
+	char input_data[MAX_INPUT_TOP];
+
+	/* input size checking */
+	if(count > MAX_INPUT_TOP - 1)
+		len = MAX_INPUT_TOP - 1;
+	else
+		len = count;
+
+	if (copy_from_user(input_data, page, len))
+		return -EFAULT;
+
+	input_data[len] = '\0';
+
+	if(!strncmp(input_data, "clear", 5))
+		timer_list_del();
+	else if(!strncmp(input_data, "start", 5))
+		start_flag = 1;
+	else if(!strncmp(input_data, "stop", 4))
+		start_flag = 0;
+
+	return len;
+}
+
+/* Print a sample string showing the possible inputs - timer_input */
+static int proc_read_timer_input(char *page, char **start, off_t off,
+                                int count, int *eof, void *data)
+{
+	int len;
+
+	len = sprintf(page, "clear start stop\n");
+
+	return len;
+}
+
+static int __init init_top_info(void)
+{
+	top_root.cache = kmem_cache_create("top_info",
+		sizeof(struct timer_top_info), 0, SLAB_PANIC, NULL, NULL);
+
+	top_info_file = create_proc_entry("timer_info", 0444, NULL);
+	if (top_info_file == NULL)
+		return -ENOMEM;
+
+	top_info_file_out = create_proc_entry("timer_input", 0666, NULL);
+	if (top_info_file_out == NULL)
+		return -ENOMEM;
+
+	/* Statistics output */
+	top_info_file->proc_fops = &proc_timertop_operations;
+
+	/* Control */
+	top_info_file_out->write_proc = &proc_write_timer_input;
+	top_info_file_out->read_proc = &proc_read_timer_input;
+
+	return 0;
+}
+
+module_init(init_top_info);
Index: linux-2.6.15-rc5-dt/lib/Kconfig.debug
===================================================================
--- linux-2.6.15-rc5-dt.orig/lib/Kconfig.debug
+++ linux-2.6.15-rc5-dt/lib/Kconfig.debug
@@ -77,6 +77,19 @@ config SCHEDSTATS
 	  application, you can say N to avoid the very slight overhead
 	  this adds.
 
+config TIMER_INFO
+	bool "Collect kernel timers statistics"
+	depends on DEBUG_KERNEL && PROC_FS && NO_IDLE_HZ
+	help
+	  If you say Y here, additional code will be inserted into the
+	  timer routines to collect statistics about kernel timers being
+	  reprogrammed through dynamic ticks feature. This statistics
+	  will be provided in /proc/timer_info and the behavior of this
+	  feature can be controlled through /proc/timer_input.
+	  The goal is to offer some output to let user applications show
+	  timers pattern usage and allow some tuning in them to
+	  maximize idle time.
+
 config DEBUG_SLAB
 	bool "Debug memory allocations"
 	depends on DEBUG_KERNEL
Attachment: pgps7ufuaaCxe.pgp
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Follow-Ups:
- Dyntick effectiveness [Was: [PATCH] i386 no idle HZ aka Dynticks 051203]
  - From: Dominik Brodowski <[email protected]>
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  - From: Dominik Brodowski <[email protected]>
- C-State policy and dynticks [Was: [PATCH] i386 no idle HZ aka Dynticks 051203]
  - From: Dominik Brodowski <[email protected]>
- Account time spent in C-States [Was: [PATCH] i386 no idle HZ aka Dynticks 051203]
  - From: Dominik Brodowski <[email protected]>
- fix cpufreq-ondemand by accounting skipped ticks as idle ticks [Was: [PATCH] i386 no idle HZ aka Dynticks 051203]
  - From: Dominik Brodowski <[email protected]>
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