diff options
| author | Pavel Tatashin | 2017-06-12 16:41:44 -0400 |
|---|---|---|
| committer | David S. Miller | 2017-06-12 15:44:02 -0700 |
| commit | 178bf2b9a20e866677bbca5cb521b09a8498c1d7 (patch) | |
| tree | c8147817fafe9eafc7ef486375eb77423666f389 | |
| parent | b5dd4d807f0fe7da67c5cc67b2ec681b60e4994b (diff) | |
sparc64: optimize loads in clock_sched()
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@oracle.com>
Reviewed-by: Shannon Nelson <shannon.nelson@oracle.com>
Reviewed-by: Steven Sistare <steven.sistare@oracle.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
| -rw-r--r-- | arch/sparc/include/asm/timer_64.h | 5 | ||||
| -rw-r--r-- | 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 fce415034000..bde2cc40ae02 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 5f53b74dd493..44e37e9f8428 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 __cacheline_aligned = { .name = "tick", .init_tick = tick_init_tick, .disable_irq = tick_disable_irq, @@ -391,9 +391,6 @@ static struct sparc64_tick_ops hbtick_operations __read_mostly = { .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) |