In clock sched we now have three loads:
- Function pointer
- quotient for multiplication
- offset
However, it is possible to improve performance substantially, by
guaranteeing that all three loads are from the same cacheline.
By moving these three values first in sparc64_tick_ops, and by having
tick_operations 64-byte aligned we guarantee this.
Signed-off-by: Pavel Tatashin <pasha.tatashin@xxxxxxxxxx>
Reviewed-by: Shannon Nelson <shannon.nelson@xxxxxxxxxx>
Reviewed-by: Steven Sistare <steven.sistare@xxxxxxxxxx>
---
arch/sparc/include/asm/timer_64.h | 5 +++++
arch/sparc/kernel/time_64.c | 17 +++++++----------
2 files changed, 12 insertions(+), 10 deletions(-)
diff --git a/arch/sparc/include/asm/timer_64.h b/arch/sparc/include/asm/timer_64.h
index fce4150..bde2cc4 100644
--- a/arch/sparc/include/asm/timer_64.h
+++ b/arch/sparc/include/asm/timer_64.h
@@ -9,7 +9,12 @@
#include <linux/types.h>
#include <linux/init.h>
+/* The most frequently accessed fields should be first,
+ * to fit into the same cacheline.
+ */
struct sparc64_tick_ops {
+ unsigned long ticks_per_nsec_quotient;
+ unsigned long offset;
unsigned long long (*get_tick)(void);
int (*add_compare)(unsigned long);
unsigned long softint_mask;
diff --git a/arch/sparc/kernel/time_64.c b/arch/sparc/kernel/time_64.c
index 5f53b74..d654f5c 100644
--- a/arch/sparc/kernel/time_64.c
+++ b/arch/sparc/kernel/time_64.c
@@ -164,7 +164,7 @@ static unsigned long tick_add_tick(unsigned long adj)
return new_tick;
}
-static struct sparc64_tick_ops tick_operations __read_mostly = {
+static struct sparc64_tick_ops tick_operations __aligned(64) __read_mostly = {
.name = "tick",
.init_tick = tick_init_tick,
.disable_irq = tick_disable_irq,
@@ -391,9 +391,6 @@ static int hbtick_add_compare(unsigned long adj)
.softint_mask = 1UL << 0,
};
-static unsigned long timer_ticks_per_nsec_quotient __read_mostly;
-static unsigned long timer_offset __read_mostly;
-
unsigned long cmos_regs;
EXPORT_SYMBOL(cmos_regs);
@@ -784,11 +781,11 @@ void __init time_init(void)
tb_ticks_per_usec = freq / USEC_PER_SEC;
- timer_ticks_per_nsec_quotient =
+ tick_operations.ticks_per_nsec_quotient =
clocksource_hz2mult(freq, SPARC64_NSEC_PER_CYC_SHIFT);
- timer_offset = (tick_operations.get_tick()
- * timer_ticks_per_nsec_quotient)
+ tick_operations.offset = (tick_operations.get_tick()
+ * tick_operations.ticks_per_nsec_quotient)
>> SPARC64_NSEC_PER_CYC_SHIFT;
clocksource_tick.name = tick_operations.name;
@@ -816,11 +813,11 @@ void __init time_init(void)
unsigned long long sched_clock(void)
{
+ unsigned long quotient = tick_operations.ticks_per_nsec_quotient;
+ unsigned long offset = tick_operations.offset;
unsigned long ticks = tick_operations.get_tick();
- return ((ticks * timer_ticks_per_nsec_quotient)
- >> SPARC64_NSEC_PER_CYC_SHIFT)
- - timer_offset;
+ return ((ticks * quotient) >> SPARC64_NSEC_PER_CYC_SHIFT) - offset;
}
int read_current_timer(unsigned long *timer_val)
--
1.7.1
--
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