Re: [PATCH] x86_64: prevent auto select of mwait_idle for AMD CPUs
On Tue, Apr 10, 2007 at 08:11:18PM +0200, Andi Kleen wrote: > On Tuesday 10 April 2007 19:24:25 Andreas Herrmann wrote: > > This fix is needed for AMD family 10h CPUs. > > > > It prevents auto select of mwait_idle for AMD CPUs. > > MWAIT does not enter C-states on family 10h and more > > power saving is reached by entering C1 with > > default_idle. > > > > The patch also adds an idle=mwait command line option > > to select mwait_idle for benchmarking. > > I already did my own patch earlier. Applied for reference. > > -Andi Great. Your patch is the better solution. Regards, Andreas - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
Re: [PATCH] x86_64: prevent auto select of mwait_idle for AMD CPUs
On Tuesday 10 April 2007 19:24:25 Andreas Herrmann wrote:
> This fix is needed for AMD family 10h CPUs.
>
> It prevents auto select of mwait_idle for AMD CPUs.
> MWAIT does not enter C-states on family 10h and more
> power saving is reached by entering C1 with
> default_idle.
>
> The patch also adds an idle=mwait command line option
> to select mwait_idle for benchmarking.
I already did my own patch earlier. Applied for reference.
-Andi
Don't use MWAIT on AMD Family 10/11
It doesn't put the CPU into deeper sleep states, so it's better to use the
standard
idle loop to save power. But allow to reenable it anyways for benchmarking.
I also removed the obsolete idle=halt
Signed-off-by: Andi Kleen <[EMAIL PROTECTED]>
Index: linux/Documentation/kernel-parameters.txt
===
--- linux.orig/Documentation/kernel-parameters.txt
+++ linux/Documentation/kernel-parameters.txt
@@ -673,8 +673,15 @@ and is between 256 and 4096 characters.
idebus= [HW] (E)IDE subsystem - VLB/PCI bus speed
See Documentation/ide.txt.
- idle= [HW]
- Format: idle=poll or idle=halt
+ idle= [X86]
+ Format: idle=poll or idle=mwait
+ 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.
+ idle=mwait. On systems which support MONITOR/MWAIT but
the kernel chose
+ 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.
ignore_loglevel [KNL]
Ignore loglevel setting - this will print /all/
Index: linux/arch/i386/kernel/cpu/amd.c
===
--- linux.orig/arch/i386/kernel/cpu/amd.c
+++ linux/arch/i386/kernel/cpu/amd.c
@@ -22,6 +22,8 @@
extern void vide(void);
__asm__(".align 4\nvide: ret");
+int force_mwait __initdata;
+
static void __cpuinit init_amd(struct cpuinfo_x86 *c)
{
u32 l, h;
@@ -241,6 +243,9 @@ static void __cpuinit init_amd(struct cp
if (cpuid_eax(0x8000) >= 0x8006)
num_cache_leaves = 3;
+
+ if ((c->x86 == 0x10 || c->x86 == 0x11) && !force_mwait)
+ clear_bit(X86_FEATURE_MWAIT, &c->x86_capability);
}
static unsigned int __cpuinit amd_size_cache(struct cpuinfo_x86 * c, unsigned
int size)
Index: linux/arch/i386/kernel/process.c
===
--- linux.orig/arch/i386/kernel/process.c
+++ linux/arch/i386/kernel/process.c
@@ -272,25 +272,24 @@ void __devinit select_idle_routine(const
}
}
-static int __init idle_setup (char *str)
+static int __init idle_setup(char *str)
{
- if (!strncmp(str, "poll", 4)) {
+ if (!strcmp(str, "poll")) {
printk("using polling idle threads.\n");
pm_idle = poll_idle;
#ifdef CONFIG_X86_SMP
if (smp_num_siblings > 1)
printk("WARNING: polling idle and HT enabled,
performance may degrade.\n");
#endif
- } else if (!strncmp(str, "halt", 4)) {
- printk("using halt in idle threads.\n");
- pm_idle = default_idle;
- }
+ } else if (!strcmp(str, "mwait"))
+ force_mwait = 1;
+ else
+ return -1;
boot_option_idle_override = 1;
- return 1;
+ return 0;
}
-
-__setup("idle=", idle_setup);
+early_param("idle", idle_setup);
void show_regs(struct pt_regs * regs)
{
Index: linux/arch/x86_64/kernel/process.c
===
--- linux.orig/arch/x86_64/kernel/process.c
+++ linux/arch/x86_64/kernel/process.c
@@ -288,16 +288,18 @@ void __cpuinit select_idle_routine(const
static int __init idle_setup (char *str)
{
- if (!strncmp(str, "poll", 4)) {
+ if (!strcmp(str, "poll")) {
printk("using polling idle threads.\n");
pm_idle = poll_idle;
- }
+ } else if (!strcmp(str, "mwait"))
+ force_mwait = 1;
+ else
+ return -1;
boot_option_idle_override = 1;
- return 1;
+ return 0;
}
-
-__setup("idle=", idle_setup);
+early_param("idle", idle_setup);
/* Prints also some state that isn't saved in the pt_regs */
void __show_regs(struct pt_regs * regs)
Index: linux/arch/x86_64/kernel/setup.c
===
--- linux.orig/arch/x86_64/kernel/setup.c
+++ linux/arch/x86_64/kernel/setup.c
@@ -79,6 +79,8 @@ int bootloader_type;
unsigned long saved_video_mode;
+i
Re: [PATCH] x86_64: prevent auto select of mwait_idle for AMD CPUs
Actually I have also written patches to clear the MWAIT flag for AMD CPUs. But after re-reading of specs (also Intel's specs) I preferred to keep the MWAIT flag but to introduce a MWAIT_NO_CSTATE flag. I think this is the cleaner solution. Regards, Andreas - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
[PATCH] x86_64: prevent auto select of mwait_idle for AMD CPUs
This fix is needed for AMD family 10h CPUs.
It prevents auto select of mwait_idle for AMD CPUs.
MWAIT does not enter C-states on family 10h and more
power saving is reached by entering C1 with
default_idle.
The patch also adds an idle=mwait command line option
to select mwait_idle for benchmarking.
Signed-off-by: Andreas Herrmann <[EMAIL PROTECTED]>
---
arch/x86_64/kernel/process.c|9 +++--
arch/x86_64/kernel/setup.c |4
include/asm-x86_64/cpufeature.h |1 +
3 files changed, 12 insertions(+), 2 deletions(-)
diff --git a/arch/x86_64/kernel/process.c b/arch/x86_64/kernel/process.c
index d8d5ccc..18fe9de 100644
--- a/arch/x86_64/kernel/process.c
+++ b/arch/x86_64/kernel/process.c
@@ -271,7 +271,8 @@ static void mwait_idle(void)
void __cpuinit select_idle_routine(const struct cpuinfo_x86 *c)
{
static int printed;
- if (cpu_has(c, X86_FEATURE_MWAIT)) {
+ if (cpu_has(c, X86_FEATURE_MWAIT) &&
+ !cpu_has(c, X86_FEATURE_MWAIT_NO_CSTATE)) {
/*
* Skip, if setup has overridden idle.
* One CPU supports mwait => All CPUs supports mwait
@@ -291,7 +292,11 @@ static int __init idle_setup (char *str)
if (!strncmp(str, "poll", 4)) {
printk("using polling idle threads.\n");
pm_idle = poll_idle;
- }
+ } else if (!strncmp(str, "mwait", 5))
+ if (boot_cpu_has(X86_FEATURE_MWAIT)) {
+ printk(KERN_INFO "using mwait in idle threads.\n");
+ pm_idle = mwait_idle;
+ }
boot_option_idle_override = 1;
return 1;
diff --git a/arch/x86_64/kernel/setup.c b/arch/x86_64/kernel/setup.c
index 3d98b69..b707025 100644
--- a/arch/x86_64/kernel/setup.c
+++ b/arch/x86_64/kernel/setup.c
@@ -612,6 +612,10 @@ static void __cpuinit init_amd(struct cpuinfo_x86 *c)
/* RDTSC can be speculated around */
clear_bit(X86_FEATURE_SYNC_RDTSC, &c->x86_capability);
+
+ /* prevent auto select of mwait_idle */
+ if (cpu_has(c, X86_FEATURE_MWAIT))
+ set_bit(X86_FEATURE_MWAIT_NO_CSTATE, c->x86_capability);
}
static void __cpuinit detect_ht(struct cpuinfo_x86 *c)
diff --git a/include/asm-x86_64/cpufeature.h b/include/asm-x86_64/cpufeature.h
index 0b3c686..9331d1a 100644
--- a/include/asm-x86_64/cpufeature.h
+++ b/include/asm-x86_64/cpufeature.h
@@ -70,6 +70,7 @@
#define X86_FEATURE_ARCH_PERFMON (3*32+9) /* Intel Architectural PerfMon */
#define X86_FEATURE_PEBS (3*32+10) /* Precise-Event Based Sampling */
#define X86_FEATURE_BTS(3*32+11) /* Branch Trace Store */
+#define X86_FEATURE_MWAIT_NO_CSTATE (3*32+12) /* mwait does not enter c-state
*/
/* Intel-defined CPU features, CPUID level 0x0001 (ecx), word 4 */
#define X86_FEATURE_XMM3 (4*32+ 0) /* Streaming SIMD Extensions-3 */
--
1.5.0.6
-
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