[PATCH] no-idle-hz aka dynamic ticks

[PATCH] no-idle-hz aka dynamic ticks

[Con Kolivas]

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As promised, here is an updated patch for the newly released 2.6.13-rc5. Boots 
and runs fine on P4HT (SMP+SMT kernel) built with gcc 4.0.1.

Cheers,
Con
---




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This is the dynamic ticks patch for i386 as written by Tony Lindgen <tony@atomide.com>
and Tuukka Tikkanen <tuukka.tikkanen@elektrobit.com>.

This version of the patch includes code style cleanups by Con Kolivas.

Signed-off-by: Con Kolivas <kernel@kolivas.org>

 arch/i386/Kconfig                   |   33 +++++
 arch/i386/kernel/Makefile           |    1
 arch/i386/kernel/apic.c             |   19 +++
 arch/i386/kernel/dyn-tick.c         |  149 +++++++++++++++++++++++++
 arch/i386/kernel/irq.c              |    3
 arch/i386/kernel/process.c          |    3
 arch/i386/kernel/time.c             |    7 -
 arch/i386/kernel/timers/timer_pit.c |   37 ++++++
 arch/i386/kernel/timers/timer_pm.c  |    4
 arch/i386/kernel/timers/timer_tsc.c |   10 +
 arch/i386/mach-default/setup.c      |   16 ++
 include/asm-i386/dyn-tick.h         |   78 +++++++++++++
 include/linux/dyn-tick.h            |   66 +++++++++++
 kernel/Makefile                     |    1
 kernel/dyn-tick.c                   |  212 ++++++++++++++++++++++++++++++++++++
 15 files changed, 636 insertions(+), 3 deletions(-)

Index: linux-2.6.13-rc5-ck1/arch/i386/Kconfig
===================================================================
--- linux-2.6.13-rc5-ck1.orig/arch/i386/Kconfig	2005-08-02 20:45:19.000000000 +1000
+++ linux-2.6.13-rc5-ck1/arch/i386/Kconfig	2005-08-02 21:14:35.000000000 +1000
@@ -457,6 +457,39 @@ config HPET_EMULATE_RTC
 	bool "Provide RTC interrupt"
 	depends on HPET_TIMER && RTC=y
 
+config NO_IDLE_HZ
+	bool "Dynamic Tick Timer - Skip timer ticks during idle"
+	depends on EXPERIMENTAL
+	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 supported timers are ACPI PM
+	  timer, local APIC timer, and TSC timer. HPET timer is currently
+	  not supported.
+
+	  Note that you need to enable dynamic tick timer either by
+	  passing dyntick=enable command line option, or via sysfs:
+
+	  # echo 1 > /sys/devices/system/timer/timer0/dyn_tick_state
+
+config DYN_TICK_USE_APIC
+	bool "Use APIC timer instead of PIT timer"
+	depends on NO_IDLE_HZ
+	help
+	  This option enables using APIC timer interrupt if your hardware
+	  supports it. APIC timer allows longer sleep periods compared
+	  to PIT timer.
+
+	  Note that on most recent hardware disabling PIT timer also
+	  disables APIC timer interrupts, and system won't run properly.
+	  Symptoms include slow system boot, and time running slow.
+
+	  If unsure, don't enable this option.
+
+	  Note that to you still need to pass dyntick=enable,forceapic
+	  command line option to use APIC timer.
+
 config SMP
 	bool "Symmetric multi-processing support"
 	---help---
Index: linux-2.6.13-rc5-ck1/arch/i386/kernel/apic.c
===================================================================
--- linux-2.6.13-rc5-ck1.orig/arch/i386/kernel/apic.c	2005-08-02 20:45:19.000000000 +1000
+++ linux-2.6.13-rc5-ck1/arch/i386/kernel/apic.c	2005-08-02 21:18:48.000000000 +1000
@@ -27,6 +27,7 @@
 #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>
@@ -931,6 +932,8 @@ void (*wait_timer_tick)(void) __devinitd
 
 #define APIC_DIVISOR 16
 
+u32 apic_timer_val;
+
 static void __setup_APIC_LVTT(unsigned int clocks)
 {
 	unsigned int lvtt_value, tmp_value, ver;
@@ -949,7 +952,12 @@ 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 / APIC_DIVISOR;
+
+	if (apic_timer_val)
+		set_dyn_tick_max_skip(apic_timer_val);
+
+	apic_write_around(APIC_TMICT, apic_timer_val);
 }
 
 static void __devinit setup_APIC_timer(unsigned int clocks)
@@ -1062,6 +1070,8 @@ void __init setup_boot_APIC_clock(void)
 	 */
 	setup_APIC_timer(calibration_result);
 
+	setup_dyn_tick_use_apic(calibration_result);
+
 	local_irq_enable();
 }
 
@@ -1200,6 +1210,13 @@ fastcall void smp_apic_timer_interrupt(s
 	 * interrupt lock, which is the WrongThing (tm) to do.
 	 */
 	irq_enter();
+
+	/*
+	 * Check if we need to wake up PIT interrupt handler.
+	 * Otherwise just wake up local APIC timer.
+	 */
+	wakeup_pit_or_apic(cpu, regs);
+
 	smp_local_timer_interrupt(regs);
 	irq_exit();
 }
Index: linux-2.6.13-rc5-ck1/arch/i386/kernel/dyn-tick.c
===================================================================
--- linux-2.6.13-rc5-ck1.orig/arch/i386/kernel/dyn-tick.c	2005-01-12 16:19:45.000000000 +1100
+++ linux-2.6.13-rc5-ck1/arch/i386/kernel/dyn-tick.c	2005-08-02 21:20:14.000000000 +1000
@@ -0,0 +1,149 @@
+/*
+ * linux/arch/i386/kernel/dyn-tick.c
+ *
+ * Copyright (C) 2004 Nokia Corporation
+ * Written by Tony Lindgen <tony@atomide.com> and
+ * Tuukka Tikkanen <tuukka.tikkanen@elektrobit.com>
+ *
+ * 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 <asm/apic.h>
+
+void arch_reprogram_timer(void)
+{
+	if (cpu_has_local_apic()) {
+		disable_pit_timer();
+		if (dyn_tick->state & DYN_TICK_TIMER_INT)
+			reprogram_apic_timer(dyn_tick->skip);
+	} else {
+		if (dyn_tick->state & DYN_TICK_TIMER_INT)
+			reprogram_pit_timer(dyn_tick->skip);
+		else
+			disable_pit_timer();
+	}
+}
+
+static struct dyn_tick_timer arch_dyn_tick_timer = {
+	.arch_reprogram_timer	= &arch_reprogram_timer,
+};
+
+int __init dyn_tick_init(void)
+{
+	arch_dyn_tick_timer.arch_init = dyn_tick_arch_init;
+	dyn_tick_register(&arch_dyn_tick_timer);
+
+	return 0;
+}
+arch_initcall(dyn_tick_init);
+
+static unsigned long long last_tick;
+
+/*
+ * This interrupt handler updates the time based on number of jiffies skipped
+ * It would be somewhat more optimized to have a customa handler in each timer
+ * using hardware ticks instead of nanoseconds. Note that CONFIG_NO_IDLE_HZ
+ * currently disables timer fallback on skipped jiffies.
+ */
+irqreturn_t dyn_tick_timer_interrupt(int irq, void *dev_id,
+					struct pt_regs *regs)
+{
+	unsigned long flags;
+	volatile unsigned long long now;
+	unsigned int skipped = 0;
+
+	write_seqlock_irqsave(&xtime_lock, flags);
+	now = cur_timer->monotonic_clock();
+	while (now - last_tick >= NS_TICK_LEN) {
+		last_tick += NS_TICK_LEN;
+		cur_timer->mark_offset();
+		do_timer_interrupt(irq, NULL, regs);
+		skipped++;
+	}
+	if (dyn_tick->state & (DYN_TICK_ENABLED | DYN_TICK_SKIPPING)) {
+		dyn_tick->skip = 1;
+		if (cpu_has_local_apic())
+			reprogram_apic_timer(dyn_tick->skip);
+		reprogram_pit_timer(dyn_tick->skip);
+		dyn_tick->state |= DYN_TICK_ENABLED;
+		dyn_tick->state &= ~DYN_TICK_SKIPPING;
+	}
+	write_sequnlock_irqrestore(&xtime_lock, flags);
+
+	return IRQ_HANDLED;
+}
+
+int __init dyn_tick_arch_init(void)
+{
+	unsigned long flags;
+
+	write_seqlock_irqsave(&xtime_lock, flags);
+	last_tick = cur_timer->monotonic_clock();
+	dyn_tick->skip = 1;
+	if (!(dyn_tick->state & DYN_TICK_USE_APIC) || !cpu_has_local_apic())
+		dyn_tick->max_skip = 0xffff / LATCH;	/* PIT timer length */
+	printk(KERN_INFO "dyn-tick: Maximum ticks to skip limited to %i\n",
+	       dyn_tick->max_skip);
+	write_sequnlock_irqrestore(&xtime_lock, flags);
+
+	dyn_tick->interrupt = dyn_tick_timer_interrupt;
+	replace_timer_interrupt(dyn_tick->interrupt);
+
+	return 0;
+}
+
+/* Functions that need blank prototypes for !CONFIG_NO_IDLE_HZ below here */
+inline void set_dyn_tick_max_skip(u32 apic_timer_val)
+{
+	dyn_tick->max_skip = 0xffffff / apic_timer_val;
+}
+
+inline void setup_dyn_tick_use_apic(unsigned int calibration_result)
+{
+	if (calibration_result)
+		dyn_tick->state |= DYN_TICK_USE_APIC;
+	else
+		printk(KERN_INFO "dyn-tick: Cannot use local APIC\n");
+}
+
+void wakeup_pit_or_apic(int cpu, struct pt_regs *regs)
+{
+	unsigned long seq; 
+
+	do {
+		seq = read_seqbegin(&xtime_lock);
+		if (dyn_tick->state & (DYN_TICK_ENABLED | DYN_TICK_SKIPPING)) {
+			if (dyn_tick->skip_cpu == cpu &&
+				dyn_tick->skip > DYN_TICK_MIN_SKIP)
+					dyn_tick->interrupt(99, NULL, regs);
+				else
+					reprogram_apic_timer(1);
+		}
+	} while (read_seqretry(&xtime_lock, seq));
+}
+
+void dyn_tick_interrupt(int irq, struct pt_regs *regs)
+{
+	if (dyn_tick->state & (DYN_TICK_ENABLED | DYN_TICK_SKIPPING) && irq)
+		dyn_tick->interrupt(irq, NULL, regs);
+}
+
+void dyn_tick_time_init(struct timer_opts *cur_timer)
+{
+	if (strncmp(cur_timer->name, "tsc", 3) == 0 ||
+	    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);
+}
Index: linux-2.6.13-rc5-ck1/arch/i386/kernel/irq.c
===================================================================
--- linux-2.6.13-rc5-ck1.orig/arch/i386/kernel/irq.c	2005-08-02 20:45:19.000000000 +1000
+++ linux-2.6.13-rc5-ck1/arch/i386/kernel/irq.c	2005-08-02 20:45:28.000000000 +1000
@@ -18,6 +18,7 @@
 #include <linux/notifier.h>
 #include <linux/cpu.h>
 #include <linux/delay.h>
+#include <linux/dyn-tick.h>
 
 DEFINE_PER_CPU(irq_cpustat_t, irq_stat) ____cacheline_maxaligned_in_smp;
 EXPORT_PER_CPU_SYMBOL(irq_stat);
@@ -76,6 +77,8 @@ fastcall unsigned int do_IRQ(struct pt_r
 	}
 #endif
 
+	dyn_tick_interrupt(irq, regs);
+
 #ifdef CONFIG_4KSTACKS
 
 	curctx = (union irq_ctx *) current_thread_info();
Index: linux-2.6.13-rc5-ck1/arch/i386/kernel/Makefile
===================================================================
--- linux-2.6.13-rc5-ck1.orig/arch/i386/kernel/Makefile	2005-08-02 20:45:19.000000000 +1000
+++ linux-2.6.13-rc5-ck1/arch/i386/kernel/Makefile	2005-08-02 20:45:28.000000000 +1000
@@ -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-2.6.13-rc5-ck1/arch/i386/kernel/process.c
===================================================================
--- linux-2.6.13-rc5-ck1.orig/arch/i386/kernel/process.c	2005-08-02 20:45:19.000000000 +1000
+++ linux-2.6.13-rc5-ck1/arch/i386/kernel/process.c	2005-08-02 21:39:28.000000000 +1000
@@ -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>
@@ -200,6 +201,8 @@ void cpu_idle(void)
 			if (cpu_is_offline(cpu))
 				play_dead();
 
+			dyn_tick_reprogram_timer();
+
 			__get_cpu_var(irq_stat).idle_timestamp = jiffies;
 			idle();
 		}
Index: linux-2.6.13-rc5-ck1/arch/i386/kernel/time.c
===================================================================
--- linux-2.6.13-rc5-ck1.orig/arch/i386/kernel/time.c	2005-08-02 20:45:19.000000000 +1000
+++ linux-2.6.13-rc5-ck1/arch/i386/kernel/time.c	2005-08-02 20:45:28.000000000 +1000
@@ -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>
@@ -252,7 +253,7 @@ 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, void *dev_id,
+inline void do_timer_interrupt(int irq, void *dev_id,
 					struct pt_regs *regs)
 {
 #ifdef CONFIG_X86_IO_APIC
@@ -423,7 +424,7 @@ 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,
 };
@@ -479,5 +480,7 @@ 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-2.6.13-rc5-ck1/arch/i386/kernel/timers/timer_pit.c
===================================================================
--- linux-2.6.13-rc5-ck1.orig/arch/i386/kernel/timers/timer_pit.c	2005-08-02 20:45:19.000000000 +1000
+++ linux-2.6.13-rc5-ck1/arch/i386/kernel/timers/timer_pit.c	2005-08-02 20:45:28.000000000 +1000
@@ -148,6 +148,43 @@ static unsigned long get_offset_pit(void
 	return count;
 }
 
+/*
+ * REVISIT: Looks like on P3 APIC timer keeps running if PIT mode
+ *	    is changed. On P4, changing PIT mode seems to kill
+ *	    APIC timer interrupts. Same thing with disabling PIT
+ *	    interrupt.
+ */
+void disable_pit_timer(void)
+{
+	extern spinlock_t i8253_lock;
+	unsigned long flags;
+	spin_lock_irqsave(&i8253_lock, flags);
+	outb_p(0x32, PIT_MODE);		/* binary, mode 1, LSB/MSB, ch 0 */
+	spin_unlock_irqrestore(&i8253_lock, flags);
+}
+
+/*
+ * 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(int 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-2.6.13-rc5-ck1/arch/i386/kernel/timers/timer_pm.c
===================================================================
--- linux-2.6.13-rc5-ck1.orig/arch/i386/kernel/timers/timer_pm.c	2005-08-02 20:45:19.000000000 +1000
+++ linux-2.6.13-rc5-ck1/arch/i386/kernel/timers/timer_pm.c	2005-08-02 20:45:28.000000000 +1000
@@ -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>
@@ -168,6 +169,9 @@ static void mark_offset_pmtmr(void)
 	monotonic_base += delta * NSEC_PER_USEC;
 	write_sequnlock(&monotonic_lock);
 
+	if (dyn_tick_enabled())
+		return;
+
 	/* convert to ticks */
 	delta += offset_delay;
 	lost = delta / (USEC_PER_SEC / HZ);
Index: linux-2.6.13-rc5-ck1/arch/i386/kernel/timers/timer_tsc.c
===================================================================
--- linux-2.6.13-rc5-ck1.orig/arch/i386/kernel/timers/timer_tsc.c	2005-08-02 20:45:19.000000000 +1000
+++ linux-2.6.13-rc5-ck1/arch/i386/kernel/timers/timer_tsc.c	2005-08-02 20:45:28.000000000 +1000
@@ -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>
@@ -367,6 +368,9 @@ static void mark_offset_tsc(void)
 
 	rdtsc(last_tsc_low, last_tsc_high);
 
+	if (dyn_tick_enabled())
+		goto monotonic_base;
+
 	spin_lock(&i8253_lock);
 	outb_p(0x00, PIT_MODE);     /* latch the count ASAP */
 
@@ -434,11 +438,17 @@ static void mark_offset_tsc(void)
 			cpufreq_delayed_get();
 	} else
 		lost_count = 0;
+
+ monotonic_base:
+
 	/* 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);
 	write_sequnlock(&monotonic_lock);
 
+	if (dyn_tick_enabled())
+		return;
+
 	/* calculate delay_at_last_interrupt */
 	count = ((LATCH-1) - count) * TICK_SIZE;
 	delay_at_last_interrupt = (count + LATCH/2) / LATCH;
Index: linux-2.6.13-rc5-ck1/arch/i386/mach-default/setup.c
===================================================================
--- linux-2.6.13-rc5-ck1.orig/arch/i386/mach-default/setup.c	2005-08-02 20:45:19.000000000 +1000
+++ linux-2.6.13-rc5-ck1/arch/i386/mach-default/setup.c	2005-08-02 21:21:22.000000000 +1000
@@ -93,6 +93,22 @@ void __init time_init_hook(void)
 	setup_irq(0, &irq0);
 }
 
+/**
+ * replace_timer_interrupt - allow replacing timer interrupt handler
+ *
+ * Description:
+ *	Can be used to replace timer interrupt handler with a more optimized
+ *	handler. Used for enabling and disabling of CONFIG_NO_IDLE_HZ.
+ */
+void replace_timer_interrupt(void *new_handler)
+{
+	unsigned long flags;
+
+	write_seqlock_irqsave(&xtime_lock, flags);
+	irq0.handler = new_handler;
+	write_sequnlock_irqrestore(&xtime_lock, flags);
+}
+
 #ifdef CONFIG_MCA
 /**
  * mca_nmi_hook - hook into MCA specific NMI chain
Index: linux-2.6.13-rc5-ck1/include/asm-i386/dyn-tick.h
===================================================================
--- linux-2.6.13-rc5-ck1.orig/include/asm-i386/dyn-tick.h	2005-01-12 16:19:45.000000000 +1100
+++ linux-2.6.13-rc5-ck1/include/asm-i386/dyn-tick.h	2005-08-02 21:43:21.000000000 +1000
@@ -0,0 +1,78 @@
+/*
+ * linux/include/asm-i386/dyn-tick.h
+ *
+ * Copyright (C) 2004 Nokia Corporation
+ * Written by Tony Lindgen <tony@atomide.com> and
+ * Tuukka Tikkanen <tuukka.tikkanen@elektrobit.com>
+ *
+ * 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_
+
+#ifdef CONFIG_NO_IDLE_HZ
+extern int dyn_tick_arch_init(void);
+extern void disable_pit_timer(void);
+extern void reprogram_pit_timer(int jiffies_to_skip);
+extern void replace_timer_interrupt(void * new_handler);
+extern void set_dyn_tick_max_skip(u32 apic_timer_val);
+extern void setup_dyn_tick_use_apic(unsigned int calibration_result);
+extern void wakeup_pit_or_apic(int cpu, struct pt_regs *regs);
+extern void dyn_tick_interrupt(int irq, struct pt_regs *regs);
+extern void dyn_tick_time_init(struct timer_opts *cur_timer);
+extern void do_timer_interrupt(int irq, void *dev_id,
+					struct pt_regs *regs);
+extern irqreturn_t dyn_tick_timer_interrupt(int irq, void *dev_id,
+					struct pt_regs *regs);
+extern int __init dyn_tick_arch_init(void);
+
+extern u32 apic_timer_val;
+
+#if defined(CONFIG_DYN_TICK_USE_APIC) && \
+	(defined(CONFIG_SMP) || defined(CONFIG_X86_UP_APIC))
+#define cpu_has_local_apic()	(dyn_tick->state & DYN_TICK_USE_APIC)
+#else
+#define cpu_has_local_apic()	0
+#endif
+
+static inline void reprogram_apic_timer(unsigned int count)
+{
+#ifdef CONFIG_X86_LOCAL_APIC
+	unsigned long flags;
+
+	count *= apic_timer_val;
+	local_irq_save(flags);
+	apic_write_around(APIC_TMICT, count);
+	local_irq_restore(flags);
+#endif	/* CONFIG_X86_LOCAL_APIC */
+}
+
+#else /* CONFIG_NO_IDLE_HZ */
+static inline void set_dyn_tick_max_skip(u32 apic_timer_val)
+{
+}
+
+static inline void reprogram_apic_timer(unsigned int count)
+{
+}
+
+static inline void setup_dyn_tick_use_apic(unsigned int calibration_result)
+{
+}
+
+static inline void wakeup_pit_or_apic(int cpu, struct pt_regs *regs)
+{
+}
+
+static inline void dyn_tick_interrupt(int irq, struct pt_regs *regs)
+{
+}
+
+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-2.6.13-rc5-ck1/include/linux/dyn-tick.h
===================================================================
--- linux-2.6.13-rc5-ck1.orig/include/linux/dyn-tick.h	2005-01-12 16:19:45.000000000 +1100
+++ linux-2.6.13-rc5-ck1/include/linux/dyn-tick.h	2005-08-02 21:41:01.000000000 +1000
@@ -0,0 +1,66 @@
+/*
+ * linux/include/linux/dyn-tick.h
+ *
+ * Copyright (C) 2004 Nokia Corporation
+ * Written by Tony Lindgen <tony@atomide.com> and
+ * Tuukka Tikkanen <tuukka.tikkanen@elektrobit.com>
+ *
+ * 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>
+#include <asm/timer.h>
+
+#define DYN_TICK_TIMER_INT	(1 << 4)
+#define DYN_TICK_USE_APIC	(1 << 3)
+#define DYN_TICK_SKIPPING	(1 << 2)
+#define DYN_TICK_ENABLED	(1 << 1)
+#define DYN_TICK_SUITABLE	(1 << 0)
+
+struct dyn_tick_state {
+	unsigned int state;		/* Current state */
+	int skip_cpu;			/* Skip handling processor */
+	unsigned long skip;		/* Ticks to skip */
+	unsigned int max_skip;		/* Max number of ticks to skip */
+	unsigned long irq_skip_mask;	/* Do not update time from these irqs */
+	irqreturn_t (*interrupt)(int, void *, struct pt_regs *);
+};
+
+struct dyn_tick_timer {
+	int (*arch_init) (void);
+	void (*arch_enable) (void);
+	void (*arch_disable) (void);
+	void (*arch_reprogram_timer) (void);
+};
+
+extern struct dyn_tick_state *dyn_tick;
+extern void dyn_tick_register(struct dyn_tick_timer *new_timer);
+
+#define NS_TICK_LEN		((1 * 1000000000)/HZ)
+#define DYN_TICK_MIN_SKIP	2
+
+
+#ifdef CONFIG_NO_IDLE_HZ
+
+extern unsigned long dyn_tick_reprogram_timer(void);
+
+#define dyn_tick_enabled()		(dyn_tick->state & DYN_TICK_ENABLED)
+
+#else
+
+#define arch_has_safe_halt()		0
+#define dyn_tick_reprogram_timer()	do {} while (0)
+#define dyn_tick_enabled()		0
+
+#endif	/* CONFIG_NO_IDLE_HZ */
+
+
+/* Pick up arch specific header */
+#include <asm/dyn-tick.h>
+
+#endif	/* _DYN_TICK_TIMER_H */
Index: linux-2.6.13-rc5-ck1/kernel/dyn-tick.c
===================================================================
--- linux-2.6.13-rc5-ck1.orig/kernel/dyn-tick.c	2005-01-12 16:19:45.000000000 +1100
+++ linux-2.6.13-rc5-ck1/kernel/dyn-tick.c	2005-08-02 21:02:44.000000000 +1000
@@ -0,0 +1,212 @@
+/*
+ * linux/kernel/dyn-tick.c
+ *
+ * Beginnings of generic dynamic tick timer support
+ *
+ * Copyright (C) 2004 Nokia Corporation
+ * Written by Tony Lindgen <tony@atomide.com> and
+ * Tuukka Tikkanen <tuukka.tikkanen@elektrobit.com>
+ *
+ * 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 <asm/io.h>
+
+#include "io_ports.h"
+
+#define DYN_TICK_VERSION	"050610-1"
+
+struct dyn_tick_state dyn_tick_state;
+struct dyn_tick_state *dyn_tick = &dyn_tick_state;
+struct dyn_tick_timer *dyn_tick_cfg;
+static cpumask_t dyn_cpu_map;
+
+/*
+ * Arch independent code needed to reprogram next timer interrupt.
+ * Gets called from cpu_idle() before entering idle loop. Note that
+ * we want to have all processors idle before reprogramming the
+ * next timer interrupt.
+ */
+unsigned long dyn_tick_reprogram_timer(void)
+{
+	int cpu;
+	unsigned long flags;
+	cpumask_t idle_cpus;
+	unsigned long next;
+
+	if (!(dyn_tick->state & DYN_TICK_ENABLED))
+		return 0;
+
+	/* Check if we are already skipping ticks and can idle other cpus */
+	if (dyn_tick->state & DYN_TICK_SKIPPING) {
+		if (cpu_has_local_apic())
+			reprogram_apic_timer(dyn_tick->skip);
+		return 0;
+	}
+
+	/* Check if we can start skipping ticks */
+	write_seqlock_irqsave(&xtime_lock, flags);
+	cpu = smp_processor_id();
+	cpu_set(cpu, dyn_cpu_map);
+	cpus_and(idle_cpus, dyn_cpu_map, cpu_online_map);
+	if (cpus_equal(idle_cpus, cpu_online_map)) {
+		next = next_timer_interrupt();
+		if (jiffies > next)
+			dyn_tick->skip = 1;
+		else
+			dyn_tick->skip = next_timer_interrupt() - jiffies;
+		if (dyn_tick->skip > DYN_TICK_MIN_SKIP) {
+			if (dyn_tick->skip > dyn_tick->max_skip)
+				dyn_tick->skip = dyn_tick->max_skip;
+
+			dyn_tick_cfg->arch_reprogram_timer();
+
+			dyn_tick->skip_cpu = cpu;
+			dyn_tick->state |= DYN_TICK_SKIPPING;
+		}
+		cpus_clear(dyn_cpu_map);
+	}
+	write_sequnlock_irqrestore(&xtime_lock, flags);
+
+	return dyn_tick->skip;
+}
+
+void __init dyn_tick_register(struct dyn_tick_timer *arch_timer)
+{
+	dyn_tick_cfg = arch_timer;
+	printk(KERN_INFO "dyn-tick: Registering dynamic tick timer v%s\n",
+	       DYN_TICK_VERSION);
+}
+
+/*
+ * ---------------------------------------------------------------------------
+ * Command line options
+ * ---------------------------------------------------------------------------
+ */
+static int __initdata dyntick_autoenable = 0;
+static int __initdata dyntick_useapic = 0;
+
+/*
+ * dyntick=[enable|disable],[forceapic]
+ */ 
+static int __init dyntick_setup(char *options)
+{
+	if (!options)
+		return 0;
+
+	if (!strncmp(options, "enable", 6)) 
+		dyntick_autoenable = 1;
+
+	if (strstr(options, "forceapic"))
+		dyntick_useapic = 1;
+
+	return 0;
+}
+
+__setup("dyntick=", dyntick_setup);
+
+/*
+ * ---------------------------------------------------------------------------
+ * Sysfs interface
+ * ---------------------------------------------------------------------------
+ */
+
+extern struct sys_device device_timer;
+
+#define DYN_TICK_IS_SET(x)	((dyn_tick->state & (x)) == (x))
+
+static ssize_t show_dyn_tick_state(struct sys_device *dev, char *buf)
+{
+	return sprintf(buf,
+		       "suitable:\t%i\n"
+		       "enabled:\t%i\n"
+		       "using APIC:\t%i\n",
+		       DYN_TICK_IS_SET(DYN_TICK_SUITABLE),
+		       DYN_TICK_IS_SET(DYN_TICK_ENABLED),
+		       DYN_TICK_IS_SET(DYN_TICK_USE_APIC));
+}
+
+static ssize_t set_dyn_tick_state(struct sys_device *dev, const char *buf,
+				size_t count)
+{
+	unsigned long flags;
+	unsigned int enable = simple_strtoul(buf, NULL, 2);
+
+	write_seqlock_irqsave(&xtime_lock, flags);
+	if (enable) {
+		if (dyn_tick_cfg->arch_enable)
+			dyn_tick_cfg->arch_enable();
+		dyn_tick->state |= DYN_TICK_ENABLED;
+	} else {
+		if (dyn_tick_cfg->arch_disable)
+			dyn_tick_cfg->arch_disable();
+		dyn_tick->state &= ~DYN_TICK_ENABLED;
+	}
+	write_sequnlock_irqrestore(&xtime_lock, flags);
+
+	return count;
+}
+
+static SYSDEV_ATTR(dyn_tick_state, 0644, show_dyn_tick_state,
+		   set_dyn_tick_state);
+
+/*
+ * ---------------------------------------------------------------------------
+ * Init functions
+ * ---------------------------------------------------------------------------
+ */
+
+static int __init dyn_tick_early_init(void)
+{
+	dyn_tick->state |= DYN_TICK_TIMER_INT;
+	return 0;
+}
+
+subsys_initcall(dyn_tick_early_init);
+
+/*
+ * We need to initialize dynamic tick after calibrate delay
+ */
+static int __init dyn_tick_late_init(void)
+{
+	int ret = 0;
+
+	if (dyn_tick_cfg == NULL || dyn_tick_cfg->arch_init == NULL ||
+	    !(dyn_tick->state & DYN_TICK_SUITABLE)) {
+		printk(KERN_ERR "dyn-tick: No suitable timer found\n");
+		return -ENODEV;
+	}
+
+	if (!dyntick_useapic)
+		dyn_tick->state &= ~DYN_TICK_USE_APIC;
+
+	ret = dyn_tick_cfg->arch_init();
+	if (ret != 0) {
+		printk(KERN_ERR "dyn-tick: Init failed\n");
+		return -ENODEV;
+	}
+
+	ret = sysdev_create_file(&device_timer, &attr_dyn_tick_state);
+
+	if (ret == 0 && 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");
+
+	return ret;
+}
+
+late_initcall(dyn_tick_late_init);
Index: linux-2.6.13-rc5-ck1/kernel/Makefile
===================================================================
--- linux-2.6.13-rc5-ck1.orig/kernel/Makefile	2005-08-02 20:45:19.000000000 +1000
+++ linux-2.6.13-rc5-ck1/kernel/Makefile	2005-08-02 20:45:28.000000000 +1000
@@ -30,6 +30,7 @@ obj-$(CONFIG_SYSFS) += ksysfs.o
 obj-$(CONFIG_GENERIC_HARDIRQS) += irq/
 obj-$(CONFIG_CRASH_DUMP) += crash_dump.o
 obj-$(CONFIG_SECCOMP) += seccomp.o
+obj-$(CONFIG_NO_IDLE_HZ) += dyn-tick.o
 
 ifneq ($(CONFIG_SCHED_NO_NO_OMIT_FRAME_POINTER),y)
 # According to Alan Modra <alan@linuxcare.com.au>, the -fno-omit-frame-pointer is

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Re: [PATCH] no-idle-hz aka dynamic ticks

[Prakash Punnoor]

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Con Kolivas schrieb:
> As promised, here is an updated patch for the newly released 2.6.13-rc5. Boots 
> and runs fine on P4HT (SMP+SMT kernel) built with gcc 4.0.1.

Doesn't compile for me w/ gcc 3.4.4:


  CC      arch/i386/kernel/irq.o
In file included from include/linux/dyn-tick.h:64,
                 from arch/i386/kernel/irq.c:21:
include/asm/dyn-tick.h: In function `reprogram_apic_timer':
include/asm/dyn-tick.h:48: warning: implicit declaration of function
`apic_write_around'
include/asm/dyn-tick.h:48: error: `APIC_TMICT' undeclared (first use in this
function)
include/asm/dyn-tick.h:48: error: (Each undeclared identifier is reported only
once
include/asm/dyn-tick.h:48: error: for each function it appears in.)
make[1]: *** [arch/i386/kernel/irq.o] Error 1


Cheers,

Prakash

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Re: [PATCH] no-idle-hz aka dynamic ticks

[Con Kolivas]

On Tue, 2 Aug 2005 22:58, Prakash Punnoor wrote:
> Con Kolivas schrieb:
> > As promised, here is an updated patch for the newly released 2.6.13-rc5.
> > Boots and runs fine on P4HT (SMP+SMT kernel) built with gcc 4.0.1.
>
> Doesn't compile for me w/ gcc 3.4.4:
>
>
>   CC      arch/i386/kernel/irq.o
> In file included from include/linux/dyn-tick.h:64,
>                  from arch/i386/kernel/irq.c:21:
> include/asm/dyn-tick.h: In function `reprogram_apic_timer':
> include/asm/dyn-tick.h:48: warning: implicit declaration of function
> `apic_write_around'
> include/asm/dyn-tick.h:48: error: `APIC_TMICT' undeclared (first use in
> this function)
> include/asm/dyn-tick.h:48: error: (Each undeclared identifier is reported
> only once
> include/asm/dyn-tick.h:48: error: for each function it appears in.)
> make[1]: *** [arch/i386/kernel/irq.o] Error 1

Please send me a .config

Cheers,
Con

[PATCH] no-idle-hz aka dynamic ticks-2

[Con Kolivas]

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On Tue, 2 Aug 2005 22:58, Prakash Punnoor wrote:
> Con Kolivas schrieb:
> > As promised, here is an updated patch for the newly released 2.6.13-rc5.
> > Boots and runs fine on P4HT (SMP+SMT kernel) built with gcc 4.0.1.
>
> Doesn't compile for me w/ gcc 3.4.4:

Thanks for the report. Tiny change required. Here is a respun patch.

Cheers,
Con
---



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Index: linux-2.6.13-rc5-ck1/arch/i386/Kconfig
===================================================================
--- linux-2.6.13-rc5-ck1.orig/arch/i386/Kconfig	2005-08-02 20:45:19.000000000 +1000
+++ linux-2.6.13-rc5-ck1/arch/i386/Kconfig	2005-08-02 21:14:35.000000000 +1000
@@ -457,6 +457,39 @@ config HPET_EMULATE_RTC
 	bool "Provide RTC interrupt"
 	depends on HPET_TIMER && RTC=y
 
+config NO_IDLE_HZ
+	bool "Dynamic Tick Timer - Skip timer ticks during idle"
+	depends on EXPERIMENTAL
+	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 supported timers are ACPI PM
+	  timer, local APIC timer, and TSC timer. HPET timer is currently
+	  not supported.
+
+	  Note that you need to enable dynamic tick timer either by
+	  passing dyntick=enable command line option, or via sysfs:
+
+	  # echo 1 > /sys/devices/system/timer/timer0/dyn_tick_state
+
+config DYN_TICK_USE_APIC
+	bool "Use APIC timer instead of PIT timer"
+	depends on NO_IDLE_HZ
+	help
+	  This option enables using APIC timer interrupt if your hardware
+	  supports it. APIC timer allows longer sleep periods compared
+	  to PIT timer.
+
+	  Note that on most recent hardware disabling PIT timer also
+	  disables APIC timer interrupts, and system won't run properly.
+	  Symptoms include slow system boot, and time running slow.
+
+	  If unsure, don't enable this option.
+
+	  Note that to you still need to pass dyntick=enable,forceapic
+	  command line option to use APIC timer.
+
 config SMP
 	bool "Symmetric multi-processing support"
 	---help---
Index: linux-2.6.13-rc5-ck1/arch/i386/kernel/apic.c
===================================================================
--- linux-2.6.13-rc5-ck1.orig/arch/i386/kernel/apic.c	2005-08-02 20:45:19.000000000 +1000
+++ linux-2.6.13-rc5-ck1/arch/i386/kernel/apic.c	2005-08-02 21:18:48.000000000 +1000
@@ -27,6 +27,7 @@
 #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>
@@ -931,6 +932,8 @@ void (*wait_timer_tick)(void) __devinitd
 
 #define APIC_DIVISOR 16
 
+u32 apic_timer_val;
+
 static void __setup_APIC_LVTT(unsigned int clocks)
 {
 	unsigned int lvtt_value, tmp_value, ver;
@@ -949,7 +952,12 @@ 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 / APIC_DIVISOR;
+
+	if (apic_timer_val)
+		set_dyn_tick_max_skip(apic_timer_val);
+
+	apic_write_around(APIC_TMICT, apic_timer_val);
 }
 
 static void __devinit setup_APIC_timer(unsigned int clocks)
@@ -1062,6 +1070,8 @@ void __init setup_boot_APIC_clock(void)
 	 */
 	setup_APIC_timer(calibration_result);
 
+	setup_dyn_tick_use_apic(calibration_result);
+
 	local_irq_enable();
 }
 
@@ -1200,6 +1210,13 @@ fastcall void smp_apic_timer_interrupt(s
 	 * interrupt lock, which is the WrongThing (tm) to do.
 	 */
 	irq_enter();
+
+	/*
+	 * Check if we need to wake up PIT interrupt handler.
+	 * Otherwise just wake up local APIC timer.
+	 */
+	wakeup_pit_or_apic(cpu, regs);
+
 	smp_local_timer_interrupt(regs);
 	irq_exit();
 }
Index: linux-2.6.13-rc5-ck1/arch/i386/kernel/dyn-tick.c
===================================================================
--- linux-2.6.13-rc5-ck1.orig/arch/i386/kernel/dyn-tick.c	2005-01-12 16:19:45.000000000 +1100
+++ linux-2.6.13-rc5-ck1/arch/i386/kernel/dyn-tick.c	2005-08-02 21:20:14.000000000 +1000
@@ -0,0 +1,149 @@
+/*
+ * linux/arch/i386/kernel/dyn-tick.c
+ *
+ * Copyright (C) 2004 Nokia Corporation
+ * Written by Tony Lindgen <tony@atomide.com> and
+ * Tuukka Tikkanen <tuukka.tikkanen@elektrobit.com>
+ *
+ * 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 <asm/apic.h>
+
+void arch_reprogram_timer(void)
+{
+	if (cpu_has_local_apic()) {
+		disable_pit_timer();
+		if (dyn_tick->state & DYN_TICK_TIMER_INT)
+			reprogram_apic_timer(dyn_tick->skip);
+	} else {
+		if (dyn_tick->state & DYN_TICK_TIMER_INT)
+			reprogram_pit_timer(dyn_tick->skip);
+		else
+			disable_pit_timer();
+	}
+}
+
+static struct dyn_tick_timer arch_dyn_tick_timer = {
+	.arch_reprogram_timer	= &arch_reprogram_timer,
+};
+
+int __init dyn_tick_init(void)
+{
+	arch_dyn_tick_timer.arch_init = dyn_tick_arch_init;
+	dyn_tick_register(&arch_dyn_tick_timer);
+
+	return 0;
+}
+arch_initcall(dyn_tick_init);
+
+static unsigned long long last_tick;
+
+/*
+ * This interrupt handler updates the time based on number of jiffies skipped
+ * It would be somewhat more optimized to have a customa handler in each timer
+ * using hardware ticks instead of nanoseconds. Note that CONFIG_NO_IDLE_HZ
+ * currently disables timer fallback on skipped jiffies.
+ */
+irqreturn_t dyn_tick_timer_interrupt(int irq, void *dev_id,
+					struct pt_regs *regs)
+{
+	unsigned long flags;
+	volatile unsigned long long now;
+	unsigned int skipped = 0;
+
+	write_seqlock_irqsave(&xtime_lock, flags);
+	now = cur_timer->monotonic_clock();
+	while (now - last_tick >= NS_TICK_LEN) {
+		last_tick += NS_TICK_LEN;
+		cur_timer->mark_offset();
+		do_timer_interrupt(irq, NULL, regs);
+		skipped++;
+	}
+	if (dyn_tick->state & (DYN_TICK_ENABLED | DYN_TICK_SKIPPING)) {
+		dyn_tick->skip = 1;
+		if (cpu_has_local_apic())
+			reprogram_apic_timer(dyn_tick->skip);
+		reprogram_pit_timer(dyn_tick->skip);
+		dyn_tick->state |= DYN_TICK_ENABLED;
+		dyn_tick->state &= ~DYN_TICK_SKIPPING;
+	}
+	write_sequnlock_irqrestore(&xtime_lock, flags);
+
+	return IRQ_HANDLED;
+}
+
+int __init dyn_tick_arch_init(void)
+{
+	unsigned long flags;
+
+	write_seqlock_irqsave(&xtime_lock, flags);
+	last_tick = cur_timer->monotonic_clock();
+	dyn_tick->skip = 1;
+	if (!(dyn_tick->state & DYN_TICK_USE_APIC) || !cpu_has_local_apic())
+		dyn_tick->max_skip = 0xffff / LATCH;	/* PIT timer length */
+	printk(KERN_INFO "dyn-tick: Maximum ticks to skip limited to %i\n",
+	       dyn_tick->max_skip);
+	write_sequnlock_irqrestore(&xtime_lock, flags);
+
+	dyn_tick->interrupt = dyn_tick_timer_interrupt;
+	replace_timer_interrupt(dyn_tick->interrupt);
+
+	return 0;
+}
+
+/* Functions that need blank prototypes for !CONFIG_NO_IDLE_HZ below here */
+inline void set_dyn_tick_max_skip(u32 apic_timer_val)
+{
+	dyn_tick->max_skip = 0xffffff / apic_timer_val;
+}
+
+inline void setup_dyn_tick_use_apic(unsigned int calibration_result)
+{
+	if (calibration_result)
+		dyn_tick->state |= DYN_TICK_USE_APIC;
+	else
+		printk(KERN_INFO "dyn-tick: Cannot use local APIC\n");
+}
+
+void wakeup_pit_or_apic(int cpu, struct pt_regs *regs)
+{
+	unsigned long seq; 
+
+	do {
+		seq = read_seqbegin(&xtime_lock);
+		if (dyn_tick->state & (DYN_TICK_ENABLED | DYN_TICK_SKIPPING)) {
+			if (dyn_tick->skip_cpu == cpu &&
+				dyn_tick->skip > DYN_TICK_MIN_SKIP)
+					dyn_tick->interrupt(99, NULL, regs);
+				else
+					reprogram_apic_timer(1);
+		}
+	} while (read_seqretry(&xtime_lock, seq));
+}
+
+void dyn_tick_interrupt(int irq, struct pt_regs *regs)
+{
+	if (dyn_tick->state & (DYN_TICK_ENABLED | DYN_TICK_SKIPPING) && irq)
+		dyn_tick->interrupt(irq, NULL, regs);
+}
+
+void dyn_tick_time_init(struct timer_opts *cur_timer)
+{
+	if (strncmp(cur_timer->name, "tsc", 3) == 0 ||
+	    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);
+}
Index: linux-2.6.13-rc5-ck1/arch/i386/kernel/irq.c
===================================================================
--- linux-2.6.13-rc5-ck1.orig/arch/i386/kernel/irq.c	2005-08-02 20:45:19.000000000 +1000
+++ linux-2.6.13-rc5-ck1/arch/i386/kernel/irq.c	2005-08-02 20:45:28.000000000 +1000
@@ -18,6 +18,7 @@
 #include <linux/notifier.h>
 #include <linux/cpu.h>
 #include <linux/delay.h>
+#include <linux/dyn-tick.h>
 
 DEFINE_PER_CPU(irq_cpustat_t, irq_stat) ____cacheline_maxaligned_in_smp;
 EXPORT_PER_CPU_SYMBOL(irq_stat);
@@ -76,6 +77,8 @@ fastcall unsigned int do_IRQ(struct pt_r
 	}
 #endif
 
+	dyn_tick_interrupt(irq, regs);
+
 #ifdef CONFIG_4KSTACKS
 
 	curctx = (union irq_ctx *) current_thread_info();
Index: linux-2.6.13-rc5-ck1/arch/i386/kernel/Makefile
===================================================================
--- linux-2.6.13-rc5-ck1.orig/arch/i386/kernel/Makefile	2005-08-02 20:45:19.000000000 +1000
+++ linux-2.6.13-rc5-ck1/arch/i386/kernel/Makefile	2005-08-02 20:45:28.000000000 +1000
@@ -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-2.6.13-rc5-ck1/arch/i386/kernel/process.c
===================================================================
--- linux-2.6.13-rc5-ck1.orig/arch/i386/kernel/process.c	2005-08-02 20:45:19.000000000 +1000
+++ linux-2.6.13-rc5-ck1/arch/i386/kernel/process.c	2005-08-02 21:39:28.000000000 +1000
@@ -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>
@@ -200,6 +201,8 @@ void cpu_idle(void)
 			if (cpu_is_offline(cpu))
 				play_dead();
 
+			dyn_tick_reprogram_timer();
+
 			__get_cpu_var(irq_stat).idle_timestamp = jiffies;
 			idle();
 		}
Index: linux-2.6.13-rc5-ck1/arch/i386/kernel/time.c
===================================================================
--- linux-2.6.13-rc5-ck1.orig/arch/i386/kernel/time.c	2005-08-02 20:45:19.000000000 +1000
+++ linux-2.6.13-rc5-ck1/arch/i386/kernel/time.c	2005-08-02 20:45:28.000000000 +1000
@@ -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>
@@ -252,7 +253,7 @@ 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, void *dev_id,
+inline void do_timer_interrupt(int irq, void *dev_id,
 					struct pt_regs *regs)
 {
 #ifdef CONFIG_X86_IO_APIC
@@ -423,7 +424,7 @@ 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,
 };
@@ -479,5 +480,7 @@ 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-2.6.13-rc5-ck1/arch/i386/kernel/timers/timer_pit.c
===================================================================
--- linux-2.6.13-rc5-ck1.orig/arch/i386/kernel/timers/timer_pit.c	2005-08-02 20:45:19.000000000 +1000
+++ linux-2.6.13-rc5-ck1/arch/i386/kernel/timers/timer_pit.c	2005-08-02 20:45:28.000000000 +1000
@@ -148,6 +148,43 @@ static unsigned long get_offset_pit(void
 	return count;
 }
 
+/*
+ * REVISIT: Looks like on P3 APIC timer keeps running if PIT mode
+ *	    is changed. On P4, changing PIT mode seems to kill
+ *	    APIC timer interrupts. Same thing with disabling PIT
+ *	    interrupt.
+ */
+void disable_pit_timer(void)
+{
+	extern spinlock_t i8253_lock;
+	unsigned long flags;
+	spin_lock_irqsave(&i8253_lock, flags);
+	outb_p(0x32, PIT_MODE);		/* binary, mode 1, LSB/MSB, ch 0 */
+	spin_unlock_irqrestore(&i8253_lock, flags);
+}
+
+/*
+ * 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(int 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-2.6.13-rc5-ck1/arch/i386/kernel/timers/timer_pm.c
===================================================================
--- linux-2.6.13-rc5-ck1.orig/arch/i386/kernel/timers/timer_pm.c	2005-08-02 20:45:19.000000000 +1000
+++ linux-2.6.13-rc5-ck1/arch/i386/kernel/timers/timer_pm.c	2005-08-02 20:45:28.000000000 +1000
@@ -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>
@@ -168,6 +169,9 @@ static void mark_offset_pmtmr(void)
 	monotonic_base += delta * NSEC_PER_USEC;
 	write_sequnlock(&monotonic_lock);
 
+	if (dyn_tick_enabled())
+		return;
+
 	/* convert to ticks */
 	delta += offset_delay;
 	lost = delta / (USEC_PER_SEC / HZ);
Index: linux-2.6.13-rc5-ck1/arch/i386/kernel/timers/timer_tsc.c
===================================================================
--- linux-2.6.13-rc5-ck1.orig/arch/i386/kernel/timers/timer_tsc.c	2005-08-02 20:45:19.000000000 +1000
+++ linux-2.6.13-rc5-ck1/arch/i386/kernel/timers/timer_tsc.c	2005-08-02 20:45:28.000000000 +1000
@@ -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>
@@ -367,6 +368,9 @@ static void mark_offset_tsc(void)
 
 	rdtsc(last_tsc_low, last_tsc_high);
 
+	if (dyn_tick_enabled())
+		goto monotonic_base;
+
 	spin_lock(&i8253_lock);
 	outb_p(0x00, PIT_MODE);     /* latch the count ASAP */
 
@@ -434,11 +438,17 @@ static void mark_offset_tsc(void)
 			cpufreq_delayed_get();
 	} else
 		lost_count = 0;
+
+ monotonic_base:
+
 	/* 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);
 	write_sequnlock(&monotonic_lock);
 
+	if (dyn_tick_enabled())
+		return;
+
 	/* calculate delay_at_last_interrupt */
 	count = ((LATCH-1) - count) * TICK_SIZE;
 	delay_at_last_interrupt = (count + LATCH/2) / LATCH;
Index: linux-2.6.13-rc5-ck1/arch/i386/mach-default/setup.c
===================================================================
--- linux-2.6.13-rc5-ck1.orig/arch/i386/mach-default/setup.c	2005-08-02 20:45:19.000000000 +1000
+++ linux-2.6.13-rc5-ck1/arch/i386/mach-default/setup.c	2005-08-02 21:21:22.000000000 +1000
@@ -93,6 +93,22 @@ void __init time_init_hook(void)
 	setup_irq(0, &irq0);
 }
 
+/**
+ * replace_timer_interrupt - allow replacing timer interrupt handler
+ *
+ * Description:
+ *	Can be used to replace timer interrupt handler with a more optimized
+ *	handler. Used for enabling and disabling of CONFIG_NO_IDLE_HZ.
+ */
+void replace_timer_interrupt(void *new_handler)
+{
+	unsigned long flags;
+
+	write_seqlock_irqsave(&xtime_lock, flags);
+	irq0.handler = new_handler;
+	write_sequnlock_irqrestore(&xtime_lock, flags);
+}
+
 #ifdef CONFIG_MCA
 /**
  * mca_nmi_hook - hook into MCA specific NMI chain
Index: linux-2.6.13-rc5-ck1/include/asm-i386/dyn-tick.h
===================================================================
--- linux-2.6.13-rc5-ck1.orig/include/asm-i386/dyn-tick.h	2005-01-12 16:19:45.000000000 +1100
+++ linux-2.6.13-rc5-ck1/include/asm-i386/dyn-tick.h	2005-08-02 23:18:49.000000000 +1000
@@ -0,0 +1,80 @@
+/*
+ * linux/include/asm-i386/dyn-tick.h
+ *
+ * Copyright (C) 2004 Nokia Corporation
+ * Written by Tony Lindgen <tony@atomide.com> and
+ * Tuukka Tikkanen <tuukka.tikkanen@elektrobit.com>
+ *
+ * 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>
+
+#ifdef CONFIG_NO_IDLE_HZ
+extern int dyn_tick_arch_init(void);
+extern void disable_pit_timer(void);
+extern void reprogram_pit_timer(int jiffies_to_skip);
+extern void replace_timer_interrupt(void * new_handler);
+extern void set_dyn_tick_max_skip(u32 apic_timer_val);
+extern void setup_dyn_tick_use_apic(unsigned int calibration_result);
+extern void wakeup_pit_or_apic(int cpu, struct pt_regs *regs);
+extern void dyn_tick_interrupt(int irq, struct pt_regs *regs);
+extern void dyn_tick_time_init(struct timer_opts *cur_timer);
+extern void do_timer_interrupt(int irq, void *dev_id,
+					struct pt_regs *regs);
+extern irqreturn_t dyn_tick_timer_interrupt(int irq, void *dev_id,
+					struct pt_regs *regs);
+extern int __init dyn_tick_arch_init(void);
+
+extern u32 apic_timer_val;
+
+#if defined(CONFIG_DYN_TICK_USE_APIC) && \
+	(defined(CONFIG_SMP) || defined(CONFIG_X86_UP_APIC))
+#define cpu_has_local_apic()	(dyn_tick->state & DYN_TICK_USE_APIC)
+#else
+#define cpu_has_local_apic()	0
+#endif
+
+static inline void reprogram_apic_timer(unsigned int count)
+{
+#ifdef CONFIG_X86_LOCAL_APIC
+	unsigned long flags;
+
+	count *= apic_timer_val;
+	local_irq_save(flags);
+	apic_write_around(APIC_TMICT, count);
+	local_irq_restore(flags);
+#endif	/* CONFIG_X86_LOCAL_APIC */
+}
+
+#else /* CONFIG_NO_IDLE_HZ */
+static inline void set_dyn_tick_max_skip(u32 apic_timer_val)
+{
+}
+
+static inline void reprogram_apic_timer(unsigned int count)
+{
+}
+
+static inline void setup_dyn_tick_use_apic(unsigned int calibration_result)
+{
+}
+
+static inline void wakeup_pit_or_apic(int cpu, struct pt_regs *regs)
+{
+}
+
+static inline void dyn_tick_interrupt(int irq, struct pt_regs *regs)
+{
+}
+
+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-2.6.13-rc5-ck1/include/linux/dyn-tick.h
===================================================================
--- linux-2.6.13-rc5-ck1.orig/include/linux/dyn-tick.h	2005-01-12 16:19:45.000000000 +1100
+++ linux-2.6.13-rc5-ck1/include/linux/dyn-tick.h	2005-08-02 21:41:01.000000000 +1000
@@ -0,0 +1,66 @@
+/*
+ * linux/include/linux/dyn-tick.h
+ *
+ * Copyright (C) 2004 Nokia Corporation
+ * Written by Tony Lindgen <tony@atomide.com> and
+ * Tuukka Tikkanen <tuukka.tikkanen@elektrobit.com>
+ *
+ * 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>
+#include <asm/timer.h>
+
+#define DYN_TICK_TIMER_INT	(1 << 4)
+#define DYN_TICK_USE_APIC	(1 << 3)
+#define DYN_TICK_SKIPPING	(1 << 2)
+#define DYN_TICK_ENABLED	(1 << 1)
+#define DYN_TICK_SUITABLE	(1 << 0)
+
+struct dyn_tick_state {
+	unsigned int state;		/* Current state */
+	int skip_cpu;			/* Skip handling processor */
+	unsigned long skip;		/* Ticks to skip */
+	unsigned int max_skip;		/* Max number of ticks to skip */
+	unsigned long irq_skip_mask;	/* Do not update time from these irqs */
+	irqreturn_t (*interrupt)(int, void *, struct pt_regs *);
+};
+
+struct dyn_tick_timer {
+	int (*arch_init) (void);
+	void (*arch_enable) (void);
+	void (*arch_disable) (void);
+	void (*arch_reprogram_timer) (void);
+};
+
+extern struct dyn_tick_state *dyn_tick;
+extern void dyn_tick_register(struct dyn_tick_timer *new_timer);
+
+#define NS_TICK_LEN		((1 * 1000000000)/HZ)
+#define DYN_TICK_MIN_SKIP	2
+
+
+#ifdef CONFIG_NO_IDLE_HZ
+
+extern unsigned long dyn_tick_reprogram_timer(void);
+
+#define dyn_tick_enabled()		(dyn_tick->state & DYN_TICK_ENABLED)
+
+#else
+
+#define arch_has_safe_halt()		0
+#define dyn_tick_reprogram_timer()	do {} while (0)
+#define dyn_tick_enabled()		0
+
+#endif	/* CONFIG_NO_IDLE_HZ */
+
+
+/* Pick up arch specific header */
+#include <asm/dyn-tick.h>
+
+#endif	/* _DYN_TICK_TIMER_H */
Index: linux-2.6.13-rc5-ck1/kernel/dyn-tick.c
===================================================================
--- linux-2.6.13-rc5-ck1.orig/kernel/dyn-tick.c	2005-01-12 16:19:45.000000000 +1100
+++ linux-2.6.13-rc5-ck1/kernel/dyn-tick.c	2005-08-02 21:02:44.000000000 +1000
@@ -0,0 +1,212 @@
+/*
+ * linux/kernel/dyn-tick.c
+ *
+ * Beginnings of generic dynamic tick timer support
+ *
+ * Copyright (C) 2004 Nokia Corporation
+ * Written by Tony Lindgen <tony@atomide.com> and
+ * Tuukka Tikkanen <tuukka.tikkanen@elektrobit.com>
+ *
+ * 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 <asm/io.h>
+
+#include "io_ports.h"
+
+#define DYN_TICK_VERSION	"050610-1"
+
+struct dyn_tick_state dyn_tick_state;
+struct dyn_tick_state *dyn_tick = &dyn_tick_state;
+struct dyn_tick_timer *dyn_tick_cfg;
+static cpumask_t dyn_cpu_map;
+
+/*
+ * Arch independent code needed to reprogram next timer interrupt.
+ * Gets called from cpu_idle() before entering idle loop. Note that
+ * we want to have all processors idle before reprogramming the
+ * next timer interrupt.
+ */
+unsigned long dyn_tick_reprogram_timer(void)
+{
+	int cpu;
+	unsigned long flags;
+	cpumask_t idle_cpus;
+	unsigned long next;
+
+	if (!(dyn_tick->state & DYN_TICK_ENABLED))
+		return 0;
+
+	/* Check if we are already skipping ticks and can idle other cpus */
+	if (dyn_tick->state & DYN_TICK_SKIPPING) {
+		if (cpu_has_local_apic())
+			reprogram_apic_timer(dyn_tick->skip);
+		return 0;
+	}
+
+	/* Check if we can start skipping ticks */
+	write_seqlock_irqsave(&xtime_lock, flags);
+	cpu = smp_processor_id();
+	cpu_set(cpu, dyn_cpu_map);
+	cpus_and(idle_cpus, dyn_cpu_map, cpu_online_map);
+	if (cpus_equal(idle_cpus, cpu_online_map)) {
+		next = next_timer_interrupt();
+		if (jiffies > next)
+			dyn_tick->skip = 1;
+		else
+			dyn_tick->skip = next_timer_interrupt() - jiffies;
+		if (dyn_tick->skip > DYN_TICK_MIN_SKIP) {
+			if (dyn_tick->skip > dyn_tick->max_skip)
+				dyn_tick->skip = dyn_tick->max_skip;
+
+			dyn_tick_cfg->arch_reprogram_timer();
+
+			dyn_tick->skip_cpu = cpu;
+			dyn_tick->state |= DYN_TICK_SKIPPING;
+		}
+		cpus_clear(dyn_cpu_map);
+	}
+	write_sequnlock_irqrestore(&xtime_lock, flags);
+
+	return dyn_tick->skip;
+}
+
+void __init dyn_tick_register(struct dyn_tick_timer *arch_timer)
+{
+	dyn_tick_cfg = arch_timer;
+	printk(KERN_INFO "dyn-tick: Registering dynamic tick timer v%s\n",
+	       DYN_TICK_VERSION);
+}
+
+/*
+ * ---------------------------------------------------------------------------
+ * Command line options
+ * ---------------------------------------------------------------------------
+ */
+static int __initdata dyntick_autoenable = 0;
+static int __initdata dyntick_useapic = 0;
+
+/*
+ * dyntick=[enable|disable],[forceapic]
+ */ 
+static int __init dyntick_setup(char *options)
+{
+	if (!options)
+		return 0;
+
+	if (!strncmp(options, "enable", 6)) 
+		dyntick_autoenable = 1;
+
+	if (strstr(options, "forceapic"))
+		dyntick_useapic = 1;
+
+	return 0;
+}
+
+__setup("dyntick=", dyntick_setup);
+
+/*
+ * ---------------------------------------------------------------------------
+ * Sysfs interface
+ * ---------------------------------------------------------------------------
+ */
+
+extern struct sys_device device_timer;
+
+#define DYN_TICK_IS_SET(x)	((dyn_tick->state & (x)) == (x))
+
+static ssize_t show_dyn_tick_state(struct sys_device *dev, char *buf)
+{
+	return sprintf(buf,
+		       "suitable:\t%i\n"
+		       "enabled:\t%i\n"
+		       "using APIC:\t%i\n",
+		       DYN_TICK_IS_SET(DYN_TICK_SUITABLE),
+		       DYN_TICK_IS_SET(DYN_TICK_ENABLED),
+		       DYN_TICK_IS_SET(DYN_TICK_USE_APIC));
+}
+
+static ssize_t set_dyn_tick_state(struct sys_device *dev, const char *buf,
+				size_t count)
+{
+	unsigned long flags;
+	unsigned int enable = simple_strtoul(buf, NULL, 2);
+
+	write_seqlock_irqsave(&xtime_lock, flags);
+	if (enable) {
+		if (dyn_tick_cfg->arch_enable)
+			dyn_tick_cfg->arch_enable();
+		dyn_tick->state |= DYN_TICK_ENABLED;
+	} else {
+		if (dyn_tick_cfg->arch_disable)
+			dyn_tick_cfg->arch_disable();
+		dyn_tick->state &= ~DYN_TICK_ENABLED;
+	}
+	write_sequnlock_irqrestore(&xtime_lock, flags);
+
+	return count;
+}
+
+static SYSDEV_ATTR(dyn_tick_state, 0644, show_dyn_tick_state,
+		   set_dyn_tick_state);
+
+/*
+ * ---------------------------------------------------------------------------
+ * Init functions
+ * ---------------------------------------------------------------------------
+ */
+
+static int __init dyn_tick_early_init(void)
+{
+	dyn_tick->state |= DYN_TICK_TIMER_INT;
+	return 0;
+}
+
+subsys_initcall(dyn_tick_early_init);
+
+/*
+ * We need to initialize dynamic tick after calibrate delay
+ */
+static int __init dyn_tick_late_init(void)
+{
+	int ret = 0;
+
+	if (dyn_tick_cfg == NULL || dyn_tick_cfg->arch_init == NULL ||
+	    !(dyn_tick->state & DYN_TICK_SUITABLE)) {
+		printk(KERN_ERR "dyn-tick: No suitable timer found\n");
+		return -ENODEV;
+	}
+
+	if (!dyntick_useapic)
+		dyn_tick->state &= ~DYN_TICK_USE_APIC;
+
+	ret = dyn_tick_cfg->arch_init();
+	if (ret != 0) {
+		printk(KERN_ERR "dyn-tick: Init failed\n");
+		return -ENODEV;
+	}
+
+	ret = sysdev_create_file(&device_timer, &attr_dyn_tick_state);
+
+	if (ret == 0 && 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");
+
+	return ret;
+}
+
+late_initcall(dyn_tick_late_init);
Index: linux-2.6.13-rc5-ck1/kernel/Makefile
===================================================================
--- linux-2.6.13-rc5-ck1.orig/kernel/Makefile	2005-08-02 20:45:19.000000000 +1000
+++ linux-2.6.13-rc5-ck1/kernel/Makefile	2005-08-02 20:45:28.000000000 +1000
@@ -30,6 +30,7 @@ obj-$(CONFIG_SYSFS) += ksysfs.o
 obj-$(CONFIG_GENERIC_HARDIRQS) += irq/
 obj-$(CONFIG_CRASH_DUMP) += crash_dump.o
 obj-$(CONFIG_SECCOMP) += seccomp.o
+obj-$(CONFIG_NO_IDLE_HZ) += dyn-tick.o
 
 ifneq ($(CONFIG_SCHED_NO_NO_OMIT_FRAME_POINTER),y)
 # According to Alan Modra <alan@linuxcare.com.au>, the -fno-omit-frame-pointer is

Re: [PATCH] no-idle-hz aka dynamic ticks

[Russell King]

On Tue, Aug 02, 2005 at 10:25:26PM +1000, Con Kolivas wrote:
> As promised, here is an updated patch for the newly released 2.6.13-rc5.
> Boots and runs fine on P4HT (SMP+SMT kernel) built with gcc 4.0.1.

Please note that ARM already has dyn-tick merged in mainline.  If
we're going to be adding dyn-tick for x86, please do it in a way
that we don't create another goddamned awful mess like we did for
the ARM IRQ stuff.

I notice that this version does some things in a different way to
the ARM version - for instance, it doesn't pass the "number of
jiffies to skip" to the arch reprogram function.

-- 
Russell King
 Linux kernel    2.6 ARM Linux   - http://www.arm.linux.org.uk/
 maintainer of:  2.6 Serial core

Re: [PATCH] no-idle-hz aka dynamic ticks

[Tony Lindgren]

* Russell King <rmk+lkml@arm.linux.org.uk> [050803 00:59]:
> On Tue, Aug 02, 2005 at 10:25:26PM +1000, Con Kolivas wrote:
> > As promised, here is an updated patch for the newly released 2.6.13-rc5.
> > Boots and runs fine on P4HT (SMP+SMT kernel) built with gcc 4.0.1.
> 
> Please note that ARM already has dyn-tick merged in mainline.  If
> we're going to be adding dyn-tick for x86, please do it in a way
> that we don't create another goddamned awful mess like we did for
> the ARM IRQ stuff.

I agree, and will be working on that :)

> I notice that this version does some things in a different way to
> the ARM version - for instance, it doesn't pass the "number of
> jiffies to skip" to the arch reprogram function.

I've been meaning to update the x86 stuff with the changes we did for
ARM as soon as I have some time.

Tony

Re: [PATCH] no-idle-hz aka dynamic ticks-2

[Pavel Machek]

Hi!

> > > As promised, here is an updated patch for the newly released 2.6.13-rc5.
> > > Boots and runs fine on P4HT (SMP+SMT kernel) built with gcc 4.0.1.
> >
> > Doesn't compile for me w/ gcc 3.4.4:
> 
> Thanks for the report. Tiny change required. Here is a respun patch.

I'm not sure if you added them, but...

  CC      arch/i386/kernel/timers/timer_tsc.o
arch/i386/kernel/timers/timer_tsc.c: In function `mark_offset_tsc':
arch/i386/kernel/timers/timer_tsc.c:345: warning: `lost' might be used uninitialized in this function
arch/i386/kernel/timers/timer_tsc.c:345: warning: `delay' might be used uninitialized in this function
arch/i386/kernel/timers/timer_tsc.c:347: warning: `count' might be used uninitialized in this function

								Pavel


-- 
teflon -- maybe it is a trademark, but it should not be.

Re: [PATCH] no-idle-hz aka dynamic ticks-2

[Pavel Machek]

Hi!

> > > As promised, here is an updated patch for the newly released 2.6.13-rc5.
> > > Boots and runs fine on P4HT (SMP+SMT kernel) built with gcc 4.0.1.
> >
> > Doesn't compile for me w/ gcc 3.4.4:
> 
> Thanks for the report. Tiny change required. Here is a respun patch.


Sorry, it breaks my machine in "interesting" way. Cursor no longer
blinks, sleep 1 takes more than five seconds, ...

Pentium-M in compaq evo n620c notebok, cpufreq active:

pavel@Elf:~$ dmesg | grep tick
dyn-tick: Found suitable timer: tsc
dyn-tick: Registering dynamic tick timer v050610-1
dyn-tick: Maximum ticks to skip limited to 13
dyn-tick: Timer not enabled during boot
pavel@Elf:~$

Ouch, even system time seems to go slower. I'll try setting
DYNTICK_USE_APIC next.
								Pavel

-- 
teflon -- maybe it is a trademark, but it should not be.

Re: [PATCH] no-idle-hz aka dynamic ticks-2

[Pavel Machek]

Hi!

> > > As promised, here is an updated patch for the newly released 2.6.13-rc5.
> > > Boots and runs fine on P4HT (SMP+SMT kernel) built with gcc 4.0.1.
> >
> > Doesn't compile for me w/ gcc 3.4.4:
> 
> Thanks for the report. Tiny change required. Here is a respun patch.

I tried  setting DYN_TICK_USE_APIC, and it got even worse. Basically
machine was frozen; if I pressed enough keys, it moved forward, then
froze again.
								Pavel

-- 
teflon -- maybe it is a trademark, but it should not be.

Re: [PATCH] no-idle-hz aka dynamic ticks-2

[Con Kolivas]

On Thu, 4 Aug 2005 07:12, Pavel Machek wrote:
> Hi!
>
> > > > As promised, here is an updated patch for the newly released
> > > > 2.6.13-rc5. Boots and runs fine on P4HT (SMP+SMT kernel) built with
> > > > gcc 4.0.1.
> > >
> > > Doesn't compile for me w/ gcc 3.4.4:
> >
> > Thanks for the report. Tiny change required. Here is a respun patch.
>
> Sorry, it breaks my machine in "interesting" way. Cursor no longer
> blinks, sleep 1 takes more than five seconds, ...
>
> Pentium-M in compaq evo n620c notebok, cpufreq active:
>
> pavel@Elf:~$ dmesg | grep tick
> dyn-tick: Found suitable timer: tsc
> dyn-tick: Registering dynamic tick timer v050610-1
> dyn-tick: Maximum ticks to skip limited to 13
> dyn-tick: Timer not enabled during boot
> pavel@Elf:~$
>
> Ouch, even system time seems to go slower. I'll try setting
> DYNTICK_USE_APIC next.
> 								Pavel

I assume you've confirmed this doesn't happen in vanilla rc5?

Cheers,
Con

Re: [PATCH] no-idle-hz aka dynamic ticks-2

[Con Kolivas]

On Thu, 4 Aug 2005 07:09 am, Pavel Machek wrote:
> Hi!
>
> > > > As promised, here is an updated patch for the newly released
> > > > 2.6.13-rc5. Boots and runs fine on P4HT (SMP+SMT kernel) built with
> > > > gcc 4.0.1.
> > >
> > > Doesn't compile for me w/ gcc 3.4.4:
> >
> > Thanks for the report. Tiny change required. Here is a respun patch.
>
> I'm not sure if you added them, but...
>
>   CC      arch/i386/kernel/timers/timer_tsc.o
> arch/i386/kernel/timers/timer_tsc.c: In function `mark_offset_tsc':
> arch/i386/kernel/timers/timer_tsc.c:345: warning: `lost' might be used
> uninitialized in this function arch/i386/kernel/timers/timer_tsc.c:345:
> warning: `delay' might be used uninitialized in this function
> arch/i386/kernel/timers/timer_tsc.c:347: warning: `count' might be used
> uninitialized in this function

Indeed the goto will bypass the setting of these variables and they will be 
uninitialised. Will fix with next version, thanks.

Con

Re: [PATCH] no-idle-hz aka dynamic ticks-2

[Con Kolivas]

On Fri, 5 Aug 2005 10:02 am, Con Kolivas wrote:
> On Thu, 4 Aug 2005 07:09 am, Pavel Machek wrote:
> > Hi!
> >
> > > > > As promised, here is an updated patch for the newly released
> > > > > 2.6.13-rc5. Boots and runs fine on P4HT (SMP+SMT kernel) built with
> > > > > gcc 4.0.1.
> > > >
> > > > Doesn't compile for me w/ gcc 3.4.4:
> > >
> > > Thanks for the report. Tiny change required. Here is a respun patch.
> >
> > I'm not sure if you added them, but...
> >
> >   CC      arch/i386/kernel/timers/timer_tsc.o
> > arch/i386/kernel/timers/timer_tsc.c: In function `mark_offset_tsc':
> > arch/i386/kernel/timers/timer_tsc.c:345: warning: `lost' might be used
> > uninitialized in this function arch/i386/kernel/timers/timer_tsc.c:345:
> > warning: `delay' might be used uninitialized in this function
> > arch/i386/kernel/timers/timer_tsc.c:347: warning: `count' might be used
> > uninitialized in this function
>
> Indeed the goto will bypass the setting of these variables and they will be
> uninitialised. Will fix with next version, thanks.

Looking yet further into this, if it gotos monotonic_base it will return 
without using any of these variables so it's a harmless warning but we may as 
well initialise them to quieten it.

Cheers,
Con

[PATCH] dyn-tick3 tweaks

[Con Kolivas]

[-- Attachment #1: Type: text/plain, Size: 367 bytes --]

On Fri, 5 Aug 2005 10:05 am, Con Kolivas wrote:
> Looking yet further into this, if it gotos monotonic_base it will return
> without using any of these variables so it's a harmless warning but we may
> as well initialise them to quieten it.

Something like this on top is cleaner and quieter. I'll add this to pending 
changes for another version.

Cheers,
Con
---



[-- Attachment #2: dtck3-tweaks.patch --]
[-- Type: text/x-diff, Size: 2420 bytes --]

Index: linux-2.6.13-rc5-ck2/arch/i386/kernel/timers/timer_tsc.c
===================================================================
--- linux-2.6.13-rc5-ck2.orig/arch/i386/kernel/timers/timer_tsc.c	2005-08-03 11:29:29.000000000 +1000
+++ linux-2.6.13-rc5-ck2/arch/i386/kernel/timers/timer_tsc.c	2005-08-05 10:22:25.000000000 +1000
@@ -167,10 +167,20 @@ 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);
+	write_sequnlock(&monotonic_lock);
+}
+
 #ifdef CONFIG_HPET_TIMER
 static void mark_offset_tsc_hpet(void)
 {
-	unsigned long long this_offset, last_offset;
+	unsigned long long last_offset;
  	unsigned long offset, temp, hpet_current;
 
 	write_seqlock(&monotonic_lock);
@@ -198,10 +208,7 @@ static void mark_offset_tsc_hpet(void)
 	}
 	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);
-	write_sequnlock(&monotonic_lock);
+	update_monotonic_base(last_offset);
 
 	/* calculate delay_at_last_interrupt */
 	/*
@@ -347,7 +354,7 @@ static void mark_offset_tsc(void)
 	int count;
 	int countmp;
 	static int count1 = 0;
-	unsigned long long this_offset, last_offset;
+	unsigned long long last_offset;
 	static int lost_count = 0;
 
 	write_seqlock(&monotonic_lock);
@@ -368,8 +375,10 @@ static void mark_offset_tsc(void)
 
 	rdtsc(last_tsc_low, last_tsc_high);
 
-	if (dyn_tick_enabled())
-		goto monotonic_base;
+	if (dyn_tick_enabled()) {
+		update_monotonic_base(last_offset);
+		return;
+	}
 
 	spin_lock(&i8253_lock);
 	outb_p(0x00, PIT_MODE);     /* latch the count ASAP */
@@ -439,15 +448,7 @@ static void mark_offset_tsc(void)
 	} else
 		lost_count = 0;
 
- monotonic_base:
-
-	/* 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);
-	write_sequnlock(&monotonic_lock);
-
-	if (dyn_tick_enabled())
-		return;
+	update_monotonic_base(last_offset);
 
 	/* calculate delay_at_last_interrupt */
 	count = ((LATCH-1) - count) * TICK_SIZE;

Re: [PATCH] dyn-tick3 tweaks

[Nick Piggin]

Con Kolivas wrote:

> Something like this on top is cleaner and quieter. I'll add this to pending 
> changes for another version.
> 
> 
> ------------------------------------------------------------------------
> 
> Index: linux-2.6.13-rc5-ck2/arch/i386/kernel/timers/timer_tsc.c
> ===================================================================
> --- linux-2.6.13-rc5-ck2.orig/arch/i386/kernel/timers/timer_tsc.c	2005-08-03 11:29:29.000000000 +1000
> +++ linux-2.6.13-rc5-ck2/arch/i386/kernel/timers/timer_tsc.c	2005-08-05 10:22:25.000000000 +1000
> @@ -167,10 +167,20 @@ 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);
> +	write_sequnlock(&monotonic_lock);
> +}
> +

All else being equal, it is much better if you unlock in the
same function that takes the lock. For readability.

It looks like you should be able to leave all the flow control
and locking the same, and use update_monotonic_base() to
do the actual update?

-- 
SUSE Labs, Novell Inc.

Send instant messages to your online friends http://au.messenger.yahoo.com 

Re: [PATCH] dyn-tick3 tweaks

[Con Kolivas]

On Fri, 5 Aug 2005 10:53 am, Nick Piggin wrote:
> Con Kolivas wrote:
> > Something like this on top is cleaner and quieter. I'll add this to
> > pending changes for another version.
> >
> >
> > ------------------------------------------------------------------------
> >
> > Index: linux-2.6.13-rc5-ck2/arch/i386/kernel/timers/timer_tsc.c
> > ===================================================================
> > ---
> > linux-2.6.13-rc5-ck2.orig/arch/i386/kernel/timers/timer_tsc.c	2005-08-03
> > 11:29:29.000000000 +1000 +++
> > linux-2.6.13-rc5-ck2/arch/i386/kernel/timers/timer_tsc.c	2005-08-05
> > 10:22:25.000000000 +1000 @@ -167,10 +167,20 @@ 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);
> > +	write_sequnlock(&monotonic_lock);
> > +}
> > +
>
> All else being equal, it is much better if you unlock in the
> same function that takes the lock. For readability.
>
> It looks like you should be able to leave all the flow control
> and locking the same, and use update_monotonic_base() to
> do the actual update?

Good advice, thanks. Will respin.

Cheers,
Con

[PATCH] dyn-tick3 tweaks respin

[Con Kolivas]

[-- Attachment #1: Type: text/plain, Size: 465 bytes --]

On Fri, 5 Aug 2005 11:39 am, Con Kolivas wrote:
> On Fri, 5 Aug 2005 10:53 am, Nick Piggin wrote:
> > All else being equal, it is much better if you unlock in the
> > same function that takes the lock. For readability.
> >
> > It looks like you should be able to leave all the flow control
> > and locking the same, and use update_monotonic_base() to
> > do the actual update?
>
> Good advice, thanks. Will respin.

Like this I assume you meant?

Cheers,
Con
---



[-- Attachment #2: dtck3-tweaks.patch --]
[-- Type: text/x-diff, Size: 2470 bytes --]

Index: linux-2.6.13-rc5-ck2/arch/i386/kernel/timers/timer_tsc.c
===================================================================
--- linux-2.6.13-rc5-ck2.orig/arch/i386/kernel/timers/timer_tsc.c	2005-08-03 11:29:29.000000000 +1000
+++ linux-2.6.13-rc5-ck2/arch/i386/kernel/timers/timer_tsc.c	2005-08-05 13:15:23.000000000 +1000
@@ -167,10 +167,19 @@ 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)
 {
-	unsigned long long this_offset, last_offset;
+	unsigned long long last_offset;
  	unsigned long offset, temp, hpet_current;
 
 	write_seqlock(&monotonic_lock);
@@ -198,9 +207,7 @@ static void mark_offset_tsc_hpet(void)
 	}
 	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 */
@@ -347,7 +354,7 @@ static void mark_offset_tsc(void)
 	int count;
 	int countmp;
 	static int count1 = 0;
-	unsigned long long this_offset, last_offset;
+	unsigned long long last_offset;
 	static int lost_count = 0;
 
 	write_seqlock(&monotonic_lock);
@@ -368,8 +375,11 @@ static void mark_offset_tsc(void)
 
 	rdtsc(last_tsc_low, last_tsc_high);
 
-	if (dyn_tick_enabled())
-		goto monotonic_base;
+	if (dyn_tick_enabled()) {
+		update_monotonic_base(last_offset);
+		write_sequnlock(&monotonic_lock);
+		return;
+	}
 
 	spin_lock(&i8253_lock);
 	outb_p(0x00, PIT_MODE);     /* latch the count ASAP */
@@ -439,16 +449,9 @@ static void mark_offset_tsc(void)
 	} else
 		lost_count = 0;
 
- monotonic_base:
-
-	/* 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);
 
-	if (dyn_tick_enabled())
-		return;
-
 	/* calculate delay_at_last_interrupt */
 	count = ((LATCH-1) - count) * TICK_SIZE;
 	delay_at_last_interrupt = (count + LATCH/2) / LATCH;

Re: [PATCH] dyn-tick3 tweaks respin

[Nick Piggin]

On Fri, 2005-08-05 at 13:20 +1000, Con Kolivas wrote:

> Like this I assume you meant?
> 

Yeah that looks good.

Nick

-- 
SUSE Labs, Novell Inc.



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