tracing: optimize global_trace_clock cachelines
The prev_trace_clock_time is only read or written to when the trace_clock_lock is taken. For better perfomance, they should share the same cache line. Reported-by: Peter Zijlstra <a.p.zijlstra@chello.nl> Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
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@ -66,10 +66,14 @@ u64 notrace trace_clock(void)
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* Used by plugins that need globally coherent timestamps.
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* Used by plugins that need globally coherent timestamps.
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*/
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*/
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static u64 prev_trace_clock_time;
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/* keep prev_time and lock in the same cacheline. */
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static struct {
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static raw_spinlock_t trace_clock_lock ____cacheline_aligned_in_smp =
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u64 prev_time;
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(raw_spinlock_t)__RAW_SPIN_LOCK_UNLOCKED;
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raw_spinlock_t lock;
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} trace_clock_struct ____cacheline_aligned_in_smp =
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{
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.lock = (raw_spinlock_t)__RAW_SPIN_LOCK_UNLOCKED,
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};
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u64 notrace trace_clock_global(void)
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u64 notrace trace_clock_global(void)
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{
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{
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@ -88,19 +92,19 @@ u64 notrace trace_clock_global(void)
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if (unlikely(in_nmi()))
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if (unlikely(in_nmi()))
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goto out;
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goto out;
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__raw_spin_lock(&trace_clock_lock);
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__raw_spin_lock(&trace_clock_struct.lock);
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/*
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/*
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* TODO: if this happens often then maybe we should reset
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* TODO: if this happens often then maybe we should reset
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* my_scd->clock to prev_trace_clock_time+1, to make sure
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* my_scd->clock to prev_time+1, to make sure
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* we start ticking with the local clock from now on?
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* we start ticking with the local clock from now on?
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*/
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*/
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if ((s64)(now - prev_trace_clock_time) < 0)
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if ((s64)(now - trace_clock_struct.prev_time) < 0)
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now = prev_trace_clock_time + 1;
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now = trace_clock_struct.prev_time + 1;
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prev_trace_clock_time = now;
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trace_clock_struct.prev_time = now;
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__raw_spin_unlock(&trace_clock_lock);
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__raw_spin_unlock(&trace_clock_struct.lock);
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out:
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out:
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raw_local_irq_restore(flags);
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raw_local_irq_restore(flags);
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