On Wed, 8 Jun 2005, Andi Kleen wrote:
> However this means __cacheline_aligned_mostly_readonly doesnt make much
> sense since there is no need for alignment in read only. How about
> replacing it with a __mostly_readonly that doesnt align and remove
> __cacheline_aligned_mostly_readonly?
Hmm. No. The bigger cpu maps may benefit from cacheline alignment for
even for read access. Here is a patch that introduces __mostly_readonly in
addition to __cacheline_aligned_mostly_readonly:
---
Create a new __mostly_readonly attribute.
Turns out that some smaller entities would also benefit from placement
with other variables that are mostly readonly. The following patch
introduces the __mostly_readonly attribute. This is simply the
__cacheline_aligned_most_readonly attribute without the cacheline
alignment.
The patch places cur_timer, hpet_usec_quotient and trickle_thresh
into that section.
Signed-off-by: Alok N Kataria <[email protected]>
Signed-off-by: Shai Fultheim <[email protected]>
Signed-off-by: Christoph Lameter <[email protected]>
Index: linux-2.6.12-rc6-mm1/arch/i386/kernel/time.c
===================================================================
--- linux-2.6.12-rc6-mm1.orig/arch/i386/kernel/time.c 2005-06-14 15:43:18.000000000 -0700
+++ linux-2.6.12-rc6-mm1/arch/i386/kernel/time.c 2005-06-14 15:43:19.000000000 -0700
@@ -88,7 +88,7 @@ EXPORT_SYMBOL(rtc_lock);
DEFINE_SPINLOCK(i8253_lock);
EXPORT_SYMBOL(i8253_lock);
-struct timer_opts *cur_timer = &timer_none;
+struct timer_opts *cur_timer __mostly_readonly = &timer_none;
/*
* This is a special lock that is owned by the CPU and holds the index
Index: linux-2.6.12-rc6-mm1/arch/i386/kernel/timers/timer_hpet.c
===================================================================
--- linux-2.6.12-rc6-mm1.orig/arch/i386/kernel/timers/timer_hpet.c 2005-06-14 15:43:18.000000000 -0700
+++ linux-2.6.12-rc6-mm1/arch/i386/kernel/timers/timer_hpet.c 2005-06-14 15:43:19.000000000 -0700
@@ -18,7 +18,9 @@
#include "mach_timer.h"
#include <asm/hpet.h>
-static unsigned long hpet_usec_quotient; /* convert hpet clks to usec */
+static unsigned long hpet_usec_quotient __mostly_readonly;
+ /* convert hpet clks to usec */
+
static unsigned long tsc_hpet_quotient; /* convert tsc to hpet clks */
static unsigned long hpet_last; /* hpet counter value at last tick*/
static unsigned long last_tsc_low; /* lsb 32 bits of Time Stamp Counter */
Index: linux-2.6.12-rc6-mm1/drivers/char/random.c
===================================================================
--- linux-2.6.12-rc6-mm1.orig/drivers/char/random.c 2005-06-14 15:43:18.000000000 -0700
+++ linux-2.6.12-rc6-mm1/drivers/char/random.c 2005-06-14 15:43:19.000000000 -0700
@@ -271,7 +271,8 @@ static int random_write_wakeup_thresh =
* samples to avoid wasting CPU time and reduce lock contention.
*/
-static int trickle_thresh = INPUT_POOL_WORDS * 28;
+static int trickle_thresh __mostly_readonly =
+ INPUT_POOL_WORDS * 28;
static DEFINE_PER_CPU(int, trickle_count) = 0;
Index: linux-2.6.12-rc6-mm1/include/linux/cache.h
===================================================================
--- linux-2.6.12-rc6-mm1.orig/include/linux/cache.h 2005-06-14 15:43:18.000000000 -0700
+++ linux-2.6.12-rc6-mm1/include/linux/cache.h 2005-06-14 15:46:58.000000000 -0700
@@ -26,9 +26,13 @@
#endif
#if defined(CONFIG_X86)
+
+#define __mostly_readonly __attribute__((__section__(".data.mostly_readonly")))
+
#define __cacheline_aligned_mostly_readonly \
__attribute__((__aligned__(SMP_CACHE_BYTES), \
__section__(".data.mostly_readonly")))
+
#else
#define __cacheline_aligned_mostly_readonly __cacheline_aligned
#endif
-
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