applied.
thanks,
-len
ps. powertop 1.9 in FC9 apparently still looks in
/proc/acpi/processor/*/power
which still shows C1/C2/C3 even when booted with "idle=halt",
and it shows no usage C1 with halt, so it shows
100% C0 time. Quite confusing.
Fortunately, powertop 1.11 looks in /sys/devices/system/cpu/cpu*/cpuidle
and displays both the correct C-states (and their type:-) plus usage.
On Tue, 24 Jun 2008, Zhao Yakui wrote:
> Subject: ACPI: Add the boot option of "idle=halt" to use halt for CPU idle
> From: Zhao Yakui <yakui.zhao@xxxxxxxxx>
>
> If the boot option of "idle=halt" is added, OSPM will be forced to use
> Halt for CPU idle. In such case CPU C2/C3 is meaningless and only C1 is used.
> At the same time halt instruction is used for CPU C1.
>
> Signed-off-by: Zhao Yakui <yakui.zhao@xxxxxxxxx>
> ---
> Documentation/kernel-parameters.txt | 4 +++-
> arch/ia64/kernel/process.c | 2 ++
> arch/x86/kernel/process.c | 17 ++++++++++++++++-
> drivers/acpi/processor_idle.c | 22 ++++++++++++++++++++++
> include/asm-ia64/processor.h | 1 +
> include/asm-x86/processor.h | 1 +
> 6 files changed, 45 insertions(+), 2 deletions(-)
>
> Index: linux-2.6/arch/x86/kernel/process.c
> ===================================================================
> --- linux-2.6.orig/arch/x86/kernel/process.c
> +++ linux-2.6/arch/x86/kernel/process.c
> @@ -6,6 +6,10 @@
> #include <linux/sched.h>
> #include <linux/module.h>
> #include <linux/pm.h>
> +#include <asm/system.h>
> +
> +unsigned long idle_halt;
> +EXPORT_SYMBOL(idle_halt);
>
> struct kmem_cache *task_xstate_cachep;
>
> @@ -169,7 +173,18 @@ static int __init idle_setup(char *str)
> pm_idle = poll_idle;
> } else if (!strcmp(str, "mwait"))
> force_mwait = 1;
> - else
> + else if (!strcmp(str, "halt")) {
> + /*
> + * When the boot option of idle=halt is added, halt is
> + * forced to be used for CPU idle. In such case CPU C2/C3
> + * won't be used again.
> + * To continue to load the CPU idle driver, don't touch
> + * the boot_option_idle_override.
> + */
> + pm_idle = default_idle;
> + idle_halt = 1;
> + return 0;
> + } else
> return -1;
>
> boot_option_idle_override = 1;
> Index: linux-2.6/Documentation/kernel-parameters.txt
> ===================================================================
> --- linux-2.6.orig/Documentation/kernel-parameters.txt
> +++ linux-2.6/Documentation/kernel-parameters.txt
> @@ -785,7 +785,7 @@ and is between 256 and 4096 characters.
> See Documentation/ide/ide.txt.
>
> idle= [X86]
> - Format: idle=poll or idle=mwait
> + Format: idle=poll or idle=mwait, idle=halt
> Poll forces a polling idle loop that can slightly improves the performance
> of waking up a idle CPU, but will use a lot of power and make the system
> run hot. Not recommended.
> @@ -793,6 +793,8 @@ and is between 256 and 4096 characters.
> to not use it because it doesn't save as much power as a normal idle
> loop use the MONITOR/MWAIT idle loop anyways. Performance should be the same
> as idle=poll.
> + idle=halt. Halt is forced to be used for CPU idle.
> + In such case C2/C3 won't be used again.
>
> ide-pci-generic.all-generic-ide [HW] (E)IDE subsystem
> Claim all unknown PCI IDE storage controllers.
> Index: linux-2.6/arch/ia64/kernel/process.c
> ===================================================================
> --- linux-2.6.orig/arch/ia64/kernel/process.c
> +++ linux-2.6/arch/ia64/kernel/process.c
> @@ -55,6 +55,8 @@ void (*ia64_mark_idle)(int);
>
> unsigned long boot_option_idle_override = 0;
> EXPORT_SYMBOL(boot_option_idle_override);
> +unsigned long idle_halt;
> +EXPORT_SYMBOL(idle_halt);
>
> void
> ia64_do_show_stack (struct unw_frame_info *info, void *arg)
> Index: linux-2.6/include/asm-ia64/processor.h
> ===================================================================
> --- linux-2.6.orig/include/asm-ia64/processor.h
> +++ linux-2.6/include/asm-ia64/processor.h
> @@ -763,6 +763,7 @@ prefetchw (const void *x)
> #define spin_lock_prefetch(x) prefetchw(x)
>
> extern unsigned long boot_option_idle_override;
> +extern unsigned long idle_halt;
>
> #endif /* !__ASSEMBLY__ */
>
> Index: linux-2.6/drivers/acpi/processor_idle.c
> ===================================================================
> --- linux-2.6.orig/drivers/acpi/processor_idle.c
> +++ linux-2.6/drivers/acpi/processor_idle.c
> @@ -41,6 +41,7 @@
> #include <linux/pm_qos_params.h>
> #include <linux/clockchips.h>
> #include <linux/cpuidle.h>
> +#include <linux/cpuidle.h>
>
> /*
> * Include the apic definitions for x86 to have the APIC timer related defines
> @@ -57,6 +58,7 @@
>
> #include <acpi/acpi_bus.h>
> #include <acpi/processor.h>
> +#include <asm/processor.h>
>
> #define ACPI_PROCESSOR_COMPONENT 0x01000000
> #define ACPI_PROCESSOR_CLASS "processor"
> @@ -955,6 +957,17 @@ static int acpi_processor_get_power_info
> } else {
> continue;
> }
> + if (cx.type == ACPI_STATE_C1 && idle_halt) {
> + /*
> + * In most cases the C1 space_id obtained from
> + * _CST object is FIXED_HARDWARE access mode.
> + * But when the option of idle=halt is added,
> + * the entry_method type should be changed from
> + * CSTATE_FFH to CSTATE_HALT.
> + */
> + cx.entry_method = ACPI_CSTATE_HALT;
> + snprintf(cx.desc, ACPI_CX_DESC_LEN, "ACPI HLT");
> + }
> } else {
> snprintf(cx.desc, ACPI_CX_DESC_LEN, "ACPI IOPORT 0x%x",
> cx.address);
> @@ -1780,6 +1793,15 @@ int __cpuinit acpi_processor_power_init(
> return 0;
>
> if (!first_run) {
> + if (idle_halt) {
> + /*
> + * When the boot option of "idle=halt" is added, halt
> + * is used for CPU IDLE.
> + * In such case C2/C3 is meaningless. So the max_cstate
> + * is set to one.
> + */
> + max_cstate = 1;
> + }
> dmi_check_system(processor_power_dmi_table);
> max_cstate = acpi_processor_cstate_check(max_cstate);
> if (max_cstate < ACPI_C_STATES_MAX)
> Index: linux-2.6/include/asm-x86/processor.h
> ===================================================================
> --- linux-2.6.orig/include/asm-x86/processor.h
> +++ linux-2.6/include/asm-x86/processor.h
> @@ -732,6 +732,7 @@ extern int force_mwait;
> extern void select_idle_routine(const struct cpuinfo_x86 *c);
>
> extern unsigned long boot_option_idle_override;
> +extern unsigned long idle_halt;
>
> extern void enable_sep_cpu(void);
> extern int sysenter_setup(void);
>
>
> --
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