[RFC][PATCH] Runtime switching to idle_poll (was: Re: 2.6.14-rt13)
From: Steven Rostedt
Date: Fri Nov 25 2005 - 16:03:27 EST
On Thu, 2005-11-24 at 16:07 +0100, Ingo Molnar wrote:
> * Steven Rostedt <rostedt@xxxxxxxxxxx> wrote:
> > Ingo, This could be a temporary patch until we come up with a better
> > solution. This adds /sys/kernel/idle/idle_poll, which if idle=poll is
> > _not_ set, it still lets you switch the machine to idle=poll on the
> > fly, as well as turn it off. If you have idle=poll, this doesn't even
> > show up.
>
> ok, i've applied this one too. Could you also submit it upstream (and
> implement it for x86)? It makes sense to enable/disable the
> polling-based idle routine runtime.
As a request from Ingo, I fixed up this patch a little to allow both
x86_64 and i386 to switch to and from idle_poll at runtime. I noticed
that the APCI driver in drivers/acpi/processor_idle.c may cause some
race condition with this patch so I added some protection there.
Basically, if the acpi code changes pm_idle, then you can't change to
idle_poll, and vice-versa.
What this patch does is creates an entry
into /sys/kernel/idle/idle_poll. It will show whether or not the
idle_poll is being used as a runtime idle routine. It is also used to
set the runtime idle.
with:
# echo 1 > /sys/kernel/idle/idle_poll
or
# echo on > /sys/kernel/idle/idle_poll
The system will switch to the idle_poll idle routine.
with:
# echo 0 > /sys/kernel/idle/idle_poll
or
# echo off > /sys/kernel/idle/idle_poll
The system will switch out of idle poll. Note that if the command line
states "idle=poll" then this will not be implemented.
This is still a work-in-progress. Since I only own a x86_64 and i386
that is all I ported the code for and tested. Looking for who else
exports pm_idle I see that the following archs may also need to be
updated:
arm, arm26, i64, sparc.
I also have not yet protected the pm_idle in arch/i386/kernel/apm.c
I figure that I should get some comments before I spend any more time on
this.
Thanks,
-- Steve
Index: linux-2.6.15-rc2-git5/arch/i386/kernel/Makefile
===================================================================
--- linux-2.6.15-rc2-git5.orig/arch/i386/kernel/Makefile 2005-10-27 20:02:08.000000000 -0400
+++ linux-2.6.15-rc2-git5/arch/i386/kernel/Makefile 2005-11-25 11:56:25.000000000 -0500
@@ -34,6 +34,7 @@
obj-$(CONFIG_HPET_TIMER) += time_hpet.o
obj-$(CONFIG_EFI) += efi.o efi_stub.o
obj-$(CONFIG_EARLY_PRINTK) += early_printk.o
+obj-$(CONFIG_SYSFS) += switch2poll.o
EXTRA_AFLAGS := -traditional
Index: linux-2.6.15-rc2-git5/arch/i386/kernel/process.c
===================================================================
--- linux-2.6.15-rc2-git5.orig/arch/i386/kernel/process.c 2005-11-25 10:58:53.000000000 -0500
+++ linux-2.6.15-rc2-git5/arch/i386/kernel/process.c 2005-11-25 12:18:12.000000000 -0500
@@ -39,6 +39,7 @@
#include <linux/ptrace.h>
#include <linux/random.h>
#include <linux/kprobes.h>
+#include <linux/spinlock.h>
#include <asm/uaccess.h>
#include <asm/pgtable.h>
@@ -64,6 +65,12 @@
unsigned long boot_option_idle_override = 0;
EXPORT_SYMBOL(boot_option_idle_override);
+spinlock_t pm_idle_switch_lock = SPIN_LOCK_UNLOCKED;
+EXPORT_SYMBOL(pm_idle_switch_lock);
+
+int pm_idle_locked = 0;
+EXPORT_SYMBOL(pm_idle_locked);
+
/*
* Return saved PC of a blocked thread.
*/
@@ -126,7 +133,7 @@
* to poll the ->work.need_resched flag instead of waiting for the
* cross-CPU IPI to arrive. Use this option with caution.
*/
-static void poll_idle (void)
+void poll_idle (void)
{
local_irq_enable();
Index: linux-2.6.15-rc2-git5/arch/i386/kernel/switch2poll.c
===================================================================
--- /dev/null 1970-01-01 00:00:00.000000000 +0000
+++ linux-2.6.15-rc2-git5/arch/i386/kernel/switch2poll.c 2005-11-25 11:55:19.000000000 -0500
@@ -0,0 +1,5 @@
+/*
+ * Same type of hack used for early_printk. This keeps the code
+ * in one place.
+ */
+#include "../../x86_64/kernel/switch2poll.c"
Index: linux-2.6.15-rc2-git5/arch/x86_64/kernel/Makefile
===================================================================
--- linux-2.6.15-rc2-git5.orig/arch/x86_64/kernel/Makefile 2005-11-22 12:13:24.000000000 -0500
+++ linux-2.6.15-rc2-git5/arch/x86_64/kernel/Makefile 2005-11-25 11:56:40.000000000 -0500
@@ -30,6 +30,7 @@
obj-$(CONFIG_DUMMY_IOMMU) += pci-nommu.o pci-dma.o
obj-$(CONFIG_KPROBES) += kprobes.o
obj-$(CONFIG_X86_PM_TIMER) += pmtimer.o
+obj-$(CONFIG_SYSFS) += switch2poll.o
obj-$(CONFIG_MODULES) += module.o
Index: linux-2.6.15-rc2-git5/arch/x86_64/kernel/process.c
===================================================================
--- linux-2.6.15-rc2-git5.orig/arch/x86_64/kernel/process.c 2005-11-25 10:58:53.000000000 -0500
+++ linux-2.6.15-rc2-git5/arch/x86_64/kernel/process.c 2005-11-25 12:17:53.000000000 -0500
@@ -36,6 +36,7 @@
#include <linux/utsname.h>
#include <linux/random.h>
#include <linux/kprobes.h>
+#include <linux/spinlock.h>
#include <asm/uaccess.h>
#include <asm/pgtable.h>
@@ -60,6 +61,12 @@
unsigned long boot_option_idle_override = 0;
EXPORT_SYMBOL(boot_option_idle_override);
+spinlock_t pm_idle_switch_lock = SPIN_LOCK_UNLOCKED;
+EXPORT_SYMBOL(pm_idle_switch_lock);
+
+int pm_idle_locked = 0;
+EXPORT_SYMBOL(pm_idle_locked);
+
/*
* Powermanagement idle function, if any..
*/
@@ -110,7 +117,7 @@
* to poll the ->need_resched flag instead of waiting for the
* cross-CPU IPI to arrive. Use this option with caution.
*/
-static void poll_idle (void)
+void poll_idle (void)
{
local_irq_enable();
Index: linux-2.6.15-rc2-git5/arch/x86_64/kernel/switch2poll.c
===================================================================
--- /dev/null 1970-01-01 00:00:00.000000000 +0000
+++ linux-2.6.15-rc2-git5/arch/x86_64/kernel/switch2poll.c 2005-11-25 12:23:22.000000000 -0500
@@ -0,0 +1,112 @@
+#include <linux/module.h>
+#include <linux/kobject.h>
+#include <linux/sysfs.h>
+#include <linux/spinlock.h>
+#include <linux/pm.h>
+
+extern void poll_idle (void);
+
+#define KERNEL_ATTR_RW(_name) \
+static struct subsys_attribute _name##_attr = \
+ __ATTR(_name, 0644, _name##_show, _name##_store)
+
+static struct idlep_kobject
+{
+ struct kobject kobj;
+ int is_poll;
+ void (*idle)(void);
+} idle_kobj;
+
+static ssize_t idle_poll_show(struct subsystem *subsys, char *page)
+{
+ return sprintf(page, "%s\n", (idle_kobj.is_poll ? "on" : "off"));
+}
+
+static ssize_t idle_poll_store(struct subsystem *subsys,
+ const char *buf, size_t len)
+{
+ unsigned long flags;
+
+ spin_lock_irqsave(&pm_idle_switch_lock, flags);
+
+ /*
+ * If power management is handling the idle function,
+ * then leave it be.
+ */
+ if (pm_idle_locked) {
+ len = -EBUSY;
+ goto out;
+ }
+
+ if (strncmp(buf,"1",1)==0 ||
+ (len >=2 && strncmp(buf,"on",2)==0)) {
+ if (idle_kobj.is_poll != 1) {
+ idle_kobj.is_poll = 1;
+ boot_option_idle_override = 1;
+ idle_kobj.idle = pm_idle;
+ pm_idle = poll_idle;
+ }
+ } else if (strncmp(buf,"0",1)==0 ||
+ (len >= 3 && strncmp(buf,"off",3)==0)) {
+ if (idle_kobj.is_poll != 0) {
+ boot_option_idle_override = 0;
+ idle_kobj.is_poll = 0;
+ pm_idle = idle_kobj.idle;
+ }
+ }
+
+out:
+ spin_unlock_irqrestore(&pm_idle_switch_lock, flags);
+
+ return len;
+}
+
+
+KERNEL_ATTR_RW(idle_poll);
+
+static struct attribute * idle_attrs[] = {
+ &idle_poll_attr.attr,
+ NULL
+};
+
+static struct attribute_group idle_attr_group = {
+ .attrs = idle_attrs,
+};
+
+static int __init idle_poll_set_init(void)
+{
+ int err;
+
+ /*
+ * If the default is alread poll_idle then
+ * don't even bother with this.
+ */
+ if (pm_idle == poll_idle)
+ return 0;
+
+ memset(&idle_kobj, 0, sizeof(idle_kobj));
+
+ idle_kobj.is_poll = 0;
+ idle_kobj.idle = pm_idle;
+
+ err = kobject_set_name(&idle_kobj.kobj, "%s", "idle");
+ if (err)
+ goto out;
+
+ idle_kobj.kobj.parent = &kernel_subsys.kset.kobj;
+ err = kobject_register(&idle_kobj.kobj);
+ if (err)
+ goto out;
+
+ err = sysfs_create_group(&idle_kobj.kobj,
+ &idle_attr_group);
+ if (err)
+ goto out;
+
+ return 0;
+out:
+ printk(KERN_INFO "Problem setting up sysfs idle_poll\n");
+ return 0;
+}
+
+late_initcall(idle_poll_set_init);
Index: linux-2.6.15-rc2-git5/drivers/acpi/processor_idle.c
===================================================================
--- linux-2.6.15-rc2-git5.orig/drivers/acpi/processor_idle.c 2005-11-22 12:13:24.000000000 -0500
+++ linux-2.6.15-rc2-git5/drivers/acpi/processor_idle.c 2005-11-25 13:15:59.000000000 -0500
@@ -38,6 +38,7 @@
#include <linux/dmi.h>
#include <linux/moduleparam.h>
#include <linux/sched.h> /* need_resched() */
+#include <linux/spinlock.h>
#include <asm/io.h>
#include <asm/uaccess.h>
@@ -990,6 +991,7 @@
static int first_run = 0;
struct proc_dir_entry *entry = NULL;
unsigned int i;
+ unsigned long flags;
ACPI_FUNCTION_TRACE("acpi_processor_power_init");
@@ -1023,6 +1025,7 @@
* Note that we use previously set idle handler will be used on
* platforms that only support C1.
*/
+ spin_lock_irqsave(&pm_idle_switch_lock, flags);
if ((pr->flags.power) && (!boot_option_idle_override)) {
printk(KERN_INFO PREFIX "CPU%d (power states:", pr->id);
for (i = 1; i <= pr->power.count; i++)
@@ -1034,8 +1037,13 @@
if (pr->id == 0) {
pm_idle_save = pm_idle;
pm_idle = acpi_processor_idle;
+ /*
+ * Don't allow switching of the pm_idle to poll.
+ */
+ pm_idle_locked = 1;
}
}
+ spin_unlock_irqrestore(&pm_idle_switch_lock, flags);
/* 'power' [R] */
entry = create_proc_entry(ACPI_PROCESSOR_FILE_POWER,
@@ -1078,5 +1086,7 @@
cpu_idle_wait();
}
+ pm_idle_locked = 0;
+
return_VALUE(0);
}
Index: linux-2.6.15-rc2-git5/include/linux/pm.h
===================================================================
--- linux-2.6.15-rc2-git5.orig/include/linux/pm.h 2005-11-25 12:05:33.000000000 -0500
+++ linux-2.6.15-rc2-git5/include/linux/pm.h 2005-11-25 12:17:17.000000000 -0500
@@ -25,6 +25,7 @@
#include <linux/config.h>
#include <linux/list.h>
+#include <linux/spinlock.h>
#include <asm/atomic.h>
/*
@@ -102,6 +103,8 @@
*/
extern void (*pm_idle)(void);
extern void (*pm_power_off)(void);
+extern spinlock_t pm_idle_switch_lock;
+extern int pm_idle_locked;
typedef int __bitwise suspend_state_t;
-
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