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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 <pasha.tatashin@oracle.com>
Reviewed-by: Steven Sistare <steven.sistare@oracle.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Pavel Tatashin 2017-06-12 16:41:48 -04:00 committed by David S. Miller
parent 4929c83a6c
commit eae3fc9871
1 changed files with 13 additions and 9 deletions
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22
arch/sparc/kernel/time_64.c
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@ -752,12 +752,10 @@ static unsigned long tb_ticks_per_usec __read_mostly;
void __delay(unsigned long loops) void __delay(unsigned long loops)
{ {
unsigned long bclock, now; unsigned long bclock = get_tick();
bclock = tick_operations.get_tick(); while ((get_tick() - bclock) < loops)
do { ;
now = tick_operations.get_tick();
} while ((now-bclock) < loops);
} }
EXPORT_SYMBOL(__delay); EXPORT_SYMBOL(__delay);
@ -769,7 +767,7 @@ EXPORT_SYMBOL(udelay);
static u64 clocksource_tick_read(struct clocksource *cs) static u64 clocksource_tick_read(struct clocksource *cs)
{ {
return tick_operations.get_tick(); return get_tick();
} }
static void __init get_tick_patch(void) 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 quotient = tick_operations.ticks_per_nsec_quotient;
unsigned long offset = tick_operations.offset; 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) int read_current_timer(unsigned long *timer_val)
{ {
*timer_val = tick_operations.get_tick(); *timer_val = get_tick();
return 0; return 0;
} }