Attachment 311847 Details for Bug 455447 – Patch for this bug

Patch for this bug

c1_idle_fix_2.patch (text/plain), 1.53 KB, created by John Villalovos on 2008-07-15 15:35:04 UTC

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Creator: John Villalovos

Created: 2008-07-15 15:35:04 UTC

Size: 1.53 KB

patch

obsolete

>
>ACPI processor_idle uses saved idle routine for C1 state, which on recent CPUs
>will be mwait_idle.
>
>mwait_idle in older kernels has a
>	while (!need_resched)
>loop, instead of
>	if (!need_resched)
>in upstream kernels.
>
>This results in older kernels, the CPU will stay in C1 for extended
>periods of time (I saw > 500 mS), unless something is scheduled to run
>on that CPU, once ACPI decides on entering C1.
>
>One fix is to change that while loop to if as in upstream. Below is alternate
>fix which is simpler and safer. With this, we come out of C1 on next tick
>(1 mS or 4 mS) and ACPI reevaluates the C-states while going to idle.
>
>Signed-off-by: Venkatesh Pallipadi <venkatesh.pallipadi@intel.com>
>
>diff -purN linux-2.6.18.x86_64.org/drivers/acpi/processor_idle.c linux-2.6.18.x86_64/drivers/acpi/processor_idle.c
>--- linux-2.6.18.x86_64.org/drivers/acpi/processor_idle.c	2006-09-19 20:42:06.000000000 -0700
>+++ linux-2.6.18.x86_64/drivers/acpi/processor_idle.c	2008-05-28 08:37:20.000000000 -0700
>@@ -247,10 +247,7 @@ static void acpi_processor_idle(void)
> 
> 	cx = pr->power.state;
> 	if (!cx) {
>-		if (pm_idle_save)
>-			pm_idle_save();
>-		else
>-			acpi_safe_halt();
>+		acpi_safe_halt();
> 		return;
> 	}
> 
>@@ -340,13 +337,8 @@ static void acpi_processor_idle(void)
> 	case ACPI_STATE_C1:
> 		/*
> 		 * Invoke C1.
>-		 * Use the appropriate idle routine, the one that would
>-		 * be used without acpi C-states.
> 		 */
>-		if (pm_idle_save)
>-			pm_idle_save();
>-		else
>-			acpi_safe_halt();
>+		acpi_safe_halt();
> 
> 		/*
> 		 * TBD: Can't get time duration while in C1, as resumes

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Attachments on bug 455447: 311847