[patch] Mark cyc2ns_scale readmostly

[patch] Mark cyc2ns_scale readmostly

[Ravikiran G Thirumalai]

This variable is rarely written to.  Mark the variable accordingly

Signed-off-by: Ravikiran Thirumalai <kiran@scalex86.org>
Signed-off-by: Shai Fultheim <shai@scalex86.org>

Index: linux-2.6.16-rc6mm1/arch/i386/kernel/tsc.c
===================================================================
--- linux-2.6.16-rc6mm1.orig/arch/i386/kernel/tsc.c	2006-03-17 11:18:53.000000000 -0800
+++ linux-2.6.16-rc6mm1/arch/i386/kernel/tsc.c	2006-03-17 11:26:35.000000000 -0800
@@ -87,7 +87,7 @@ EXPORT_SYMBOL_GPL(mark_tsc_unstable);
  *
  *			-johnstul@us.ibm.com "math is hard, lets go shopping!"
  */
-static unsigned long cyc2ns_scale;
+static unsigned long cyc2ns_scale __read_mostly;
 
 #define CYC2NS_SCALE_FACTOR 10 /* 2^10, carefully chosen */
 
Index: linux-2.6.16-rc6mm1/arch/x86_64/kernel/time.c
===================================================================
--- linux-2.6.16-rc6mm1.orig/arch/x86_64/kernel/time.c	2006-03-17 11:18:53.000000000 -0800
+++ linux-2.6.16-rc6mm1/arch/x86_64/kernel/time.c	2006-03-17 11:23:07.000000000 -0800
@@ -467,7 +467,7 @@ static irqreturn_t timer_interrupt(int i
 	return IRQ_HANDLED;
 }
 
-static unsigned int cyc2ns_scale;
+static unsigned int cyc2ns_scale __read_mostly;
 #define CYC2NS_SCALE_FACTOR 10 /* 2^10, carefully chosen */
 
 static inline void set_cyc2ns_scale(unsigned long cpu_khz)

Re: [patch] Mark cyc2ns_scale readmostly

[Andrew Morton]

Ravikiran G Thirumalai <kiran@scalex86.org> wrote:
>
> This variable is rarely written to.  Mark the variable accordingly
>

I dropped all John's timekeeping patches today - he's redoing everything. 
So I've reworked this against mainline.

x86 actually has two cyc2ns_scale's.

 arch/i386/kernel/timers/timer_hpet.c |    2 +-
 arch/i386/kernel/timers/timer_tsc.c  |    2 +-
 arch/x86_64/kernel/time.c            |    2 +-
 3 files changed, 3 insertions(+), 3 deletions(-)

diff -puN arch/i386/kernel/timers/timer_hpet.c~mark-cyc2ns_scale-readmostly arch/i386/kernel/timers/timer_hpet.c
--- devel/arch/i386/kernel/timers/timer_hpet.c~mark-cyc2ns_scale-readmostly	2006-03-17 21:34:19.000000000 -0800
+++ devel-akpm/arch/i386/kernel/timers/timer_hpet.c	2006-03-17 21:34:19.000000000 -0800
@@ -46,7 +46,7 @@ static seqlock_t monotonic_lock = SEQLOC
  *
  *			-johnstul@us.ibm.com "math is hard, lets go shopping!"
  */
-static unsigned long cyc2ns_scale;
+static unsigned long cyc2ns_scale __read_mostly;
 #define CYC2NS_SCALE_FACTOR 10 /* 2^10, carefully chosen */
 
 static inline void set_cyc2ns_scale(unsigned long cpu_khz)
diff -puN arch/i386/kernel/timers/timer_tsc.c~mark-cyc2ns_scale-readmostly arch/i386/kernel/timers/timer_tsc.c
--- devel/arch/i386/kernel/timers/timer_tsc.c~mark-cyc2ns_scale-readmostly	2006-03-17 21:34:19.000000000 -0800
+++ devel-akpm/arch/i386/kernel/timers/timer_tsc.c	2006-03-17 21:34:19.000000000 -0800
@@ -74,7 +74,7 @@ late_initcall(start_lost_tick_compensati
  *
  *			-johnstul@us.ibm.com "math is hard, lets go shopping!"
  */
-static unsigned long cyc2ns_scale; 
+static unsigned long cyc2ns_scale __read_mostly;
 #define CYC2NS_SCALE_FACTOR 10 /* 2^10, carefully chosen */
 
 static inline void set_cyc2ns_scale(unsigned long cpu_khz)
diff -puN arch/x86_64/kernel/time.c~mark-cyc2ns_scale-readmostly arch/x86_64/kernel/time.c
--- devel/arch/x86_64/kernel/time.c~mark-cyc2ns_scale-readmostly	2006-03-17 21:34:19.000000000 -0800
+++ devel-akpm/arch/x86_64/kernel/time.c	2006-03-17 21:34:19.000000000 -0800
@@ -477,7 +477,7 @@ static irqreturn_t timer_interrupt(int i
 	return IRQ_HANDLED;
 }
 
-static unsigned int cyc2ns_scale;
+static unsigned int cyc2ns_scale __read_mostly;
 #define CYC2NS_SCALE_FACTOR 10 /* 2^10, carefully chosen */
 
 static inline void set_cyc2ns_scale(unsigned long cpu_khz)
_