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Subject[PATCH] raise tsc clocksource rating
Date
From: Glauber de Oliveira Costa <glauber@t60.localdomain>

tsc is very good time source (when it does not have drifts, does not
change it's frequency, i.e. when it works), so it should have its rating
raised to a value greater than, or equal 400.

Since it's being a tendency among paravirt clocksources to use values
around 400, we should declare tsc as even better: So we use 500.

This patch also touches the comments on clocksource.h, which suggests
that 499 would be a limit on the rating values.

Signed-off-by: Glauber de Oliveira Costa <gcosta@redhat.com>
---
arch/x86/kernel/tsc_32.c | 2 +-
arch/x86/kernel/tsc_64.c | 2 +-
include/linux/clocksource.h | 2 +-
3 files changed, 3 insertions(+), 3 deletions(-)

diff --git a/arch/x86/kernel/tsc_32.c b/arch/x86/kernel/tsc_32.c
index 9ebc0da..4d91e59 100644
--- a/arch/x86/kernel/tsc_32.c
+++ b/arch/x86/kernel/tsc_32.c
@@ -280,7 +280,7 @@ static cycle_t read_tsc(void)

static struct clocksource clocksource_tsc = {
.name = "tsc",
- .rating = 300,
+ .rating = 500,
.read = read_tsc,
.mask = CLOCKSOURCE_MASK(64),
.mult = 0, /* to be set */
diff --git a/arch/x86/kernel/tsc_64.c b/arch/x86/kernel/tsc_64.c
index 9c70af4..4fd5b1b 100644
--- a/arch/x86/kernel/tsc_64.c
+++ b/arch/x86/kernel/tsc_64.c
@@ -262,7 +262,7 @@ static cycle_t __vsyscall_fn vread_tsc(void)

static struct clocksource clocksource_tsc = {
.name = "tsc",
- .rating = 300,
+ .rating = 500,
.read = read_tsc,
.mask = CLOCKSOURCE_MASK(64),
.shift = 22,
diff --git a/include/linux/clocksource.h b/include/linux/clocksource.h
index 107787a..5b0aadd 100644
--- a/include/linux/clocksource.h
+++ b/include/linux/clocksource.h
@@ -39,7 +39,7 @@ struct clocksource;
* A correct and usable clocksource.
* 300-399: Desired.
* A reasonably fast and accurate clocksource.
- * 400-499: Perfect
+ * >= 400 : Perfect
* The ideal clocksource. A must-use where
* available.
* @read: returns a cycle value
--
1.5.0.6
-
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