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authorIngo Molnar <mingo@elte.hu>2008-05-12 15:20:48 -0400
committerThomas Gleixner <tglx@linutronix.de>2008-05-23 14:54:37 -0400
commit0fd9e0dac9026df09986a4b201518ae015814aef (patch)
treebbc20440973ac0196818a9a1b91fde17148fd8fd /kernel/trace/trace.c
parent26994ead1fc8cced63f17e9848edc1771036664e (diff)
ftrace: use cpu clock again
Signed-off-by: Ingo Molnar <mingo@elte.hu> Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Diffstat (limited to 'kernel/trace/trace.c')
-rw-r--r--kernel/trace/trace.c54
1 files changed, 1 insertions, 53 deletions
diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
index 3dc6eac85b11..d74c039305ad 100644
--- a/kernel/trace/trace.c
+++ b/kernel/trace/trace.c
@@ -42,61 +42,9 @@ ns2usecs(cycle_t nsec)
42 return nsec; 42 return nsec;
43} 43}
44 44
45static const int time_sync_freq_max = 128;
46static const cycle_t time_sync_thresh = 100000;
47
48static DEFINE_PER_CPU(cycle_t, time_offset);
49static DEFINE_PER_CPU(cycle_t, prev_cpu_time);
50static DEFINE_PER_CPU(int, time_sync_count);
51static DEFINE_PER_CPU(int, time_sync_freq);
52
53/*
54 * Global lock which we take every now and then to synchronize
55 * the CPUs time. This method is not warp-safe, but it's good
56 * enough to synchronize slowly diverging time sources and thus
57 * it's good enough for tracing:
58 */
59static DEFINE_SPINLOCK(time_sync_lock);
60static cycle_t prev_global_time;
61
62static notrace cycle_t __ftrace_now_sync(cycles_t time, int cpu)
63{
64 unsigned long flags;
65
66 spin_lock_irqsave(&time_sync_lock, flags);
67
68 /*
69 * Update the synchronization frequency:
70 */
71 if (per_cpu(time_sync_freq, cpu) < time_sync_freq_max)
72 per_cpu(time_sync_freq, cpu) *= 2;
73 per_cpu(time_sync_count, cpu) = per_cpu(time_sync_freq, cpu);
74
75 if (time < prev_global_time) {
76 per_cpu(time_offset, cpu) += prev_global_time - time;
77 time = prev_global_time;
78 } else {
79 prev_global_time = time;
80 }
81
82 spin_unlock_irqrestore(&time_sync_lock, flags);
83
84 return time;
85}
86
87notrace cycle_t ftrace_now(int cpu) 45notrace cycle_t ftrace_now(int cpu)
88{ 46{
89 cycle_t prev_cpu_time, time, delta_time; 47 return cpu_clock(cpu);
90
91 prev_cpu_time = per_cpu(prev_cpu_time, cpu);
92 time = sched_clock() + per_cpu(time_offset, cpu);
93 delta_time = time-prev_cpu_time;
94
95 if (unlikely(delta_time > time_sync_thresh ||
96 --per_cpu(time_sync_count, cpu) <= 0))
97 time = __ftrace_now_sync(time, cpu);
98
99 return time;
100} 48}
101 49
102static struct trace_array global_trace; 50static struct trace_array global_trace;