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>
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@ -9,7 +9,12 @@
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#include <linux/types.h>
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#include <linux/init.h>
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/* The most frequently accessed fields should be first,
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* to fit into the same cacheline.
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*/
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struct sparc64_tick_ops {
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unsigned long ticks_per_nsec_quotient;
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unsigned long offset;
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unsigned long long (*get_tick)(void);
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int (*add_compare)(unsigned long);
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unsigned long softint_mask;
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@ -164,7 +164,7 @@ static unsigned long tick_add_tick(unsigned long adj)
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return new_tick;
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}
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static struct sparc64_tick_ops tick_operations __read_mostly = {
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static struct sparc64_tick_ops tick_operations __cacheline_aligned = {
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.name = "tick",
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.init_tick = tick_init_tick,
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.disable_irq = tick_disable_irq,
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@ -391,9 +391,6 @@ static struct sparc64_tick_ops hbtick_operations __read_mostly = {
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.softint_mask = 1UL << 0,
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};
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static unsigned long timer_ticks_per_nsec_quotient __read_mostly;
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static unsigned long timer_offset __read_mostly;
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unsigned long cmos_regs;
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EXPORT_SYMBOL(cmos_regs);
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@ -784,11 +781,11 @@ void __init time_init(void)
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tb_ticks_per_usec = freq / USEC_PER_SEC;
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timer_ticks_per_nsec_quotient =
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tick_operations.ticks_per_nsec_quotient =
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clocksource_hz2mult(freq, SPARC64_NSEC_PER_CYC_SHIFT);
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timer_offset = (tick_operations.get_tick()
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* timer_ticks_per_nsec_quotient)
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tick_operations.offset = (tick_operations.get_tick()
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* tick_operations.ticks_per_nsec_quotient)
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>> SPARC64_NSEC_PER_CYC_SHIFT;
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clocksource_tick.name = tick_operations.name;
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@ -816,11 +813,11 @@ void __init time_init(void)
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unsigned long long sched_clock(void)
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{
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unsigned long quotient = tick_operations.ticks_per_nsec_quotient;
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unsigned long offset = tick_operations.offset;
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unsigned long ticks = tick_operations.get_tick();
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return ((ticks * timer_ticks_per_nsec_quotient)
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>> SPARC64_NSEC_PER_CYC_SHIFT)
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- timer_offset;
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return ((ticks * quotient) >> SPARC64_NSEC_PER_CYC_SHIFT) - offset;
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}
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int read_current_timer(unsigned long *timer_val)
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