From eae3fc9871111e9bbc77dad5481a3e805e02ac46 Mon Sep 17 00:00:00 2001 From: Pavel Tatashin Date: Mon, 12 Jun 2017 16:41:48 -0400 Subject: [PATCH] sparc64: optimize functions that access tick Replace read tick function pointers with the new hot-patched get_tick(). This optimizes the performance of functions such as: sched_clock() Signed-off-by: Pavel Tatashin Reviewed-by: Steven Sistare Signed-off-by: David S. Miller --- arch/sparc/kernel/time_64.c | 22 +++++++++++++--------- 1 file changed, 13 insertions(+), 9 deletions(-) diff --git a/arch/sparc/kernel/time_64.c b/arch/sparc/kernel/time_64.c index ca27415c393a..a612a91cb9cd 100644 --- a/arch/sparc/kernel/time_64.c +++ b/arch/sparc/kernel/time_64.c @@ -752,12 +752,10 @@ static unsigned long tb_ticks_per_usec __read_mostly; void __delay(unsigned long loops) { - unsigned long bclock, now; + unsigned long bclock = get_tick(); - bclock = tick_operations.get_tick(); - do { - now = tick_operations.get_tick(); - } while ((now-bclock) < loops); + while ((get_tick() - bclock) < loops) + ; } EXPORT_SYMBOL(__delay); @@ -769,7 +767,7 @@ EXPORT_SYMBOL(udelay); static u64 clocksource_tick_read(struct clocksource *cs) { - return tick_operations.get_tick(); + return get_tick(); } static void __init get_tick_patch(void) @@ -853,13 +851,19 @@ 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 * quotient) >> SPARC64_NSEC_PER_CYC_SHIFT) - offset; + /* Use barrier so the compiler emits the loads first and overlaps load + * latency with reading tick, because reading %tick/%stick is a + * post-sync instruction that will flush and restart subsequent + * instructions after it commits. + */ + barrier(); + + return ((get_tick() * quotient) >> SPARC64_NSEC_PER_CYC_SHIFT) - offset; } int read_current_timer(unsigned long *timer_val) { - *timer_val = tick_operations.get_tick(); + *timer_val = get_tick(); return 0; } -- 2.20.1