ftrace: remove-idx-sync

remove idx syncing - it's expensive on SMP.

Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>

diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
index 9a931c7c2da31472bae5af55f7608bd1b466486e..ce8ceb8aea6afc7b50d5a638beb3b99b01267c1d 100644 (file)
--- a/kernel/trace/trace.c
+++ b/kernel/trace/trace.c
@@ -99,7 +99,6 @@ notrace cycle_t ftrace_now(int cpu)
        return time;
 }
 
-static atomic_t                        tracer_counter;
 static struct trace_array      global_trace;
 
 static DEFINE_PER_CPU(struct trace_array_cpu, global_trace_cpu);
@@ -661,7 +660,6 @@ tracing_generic_entry_update(struct trace_entry *entry, unsigned long flags)
 
        pc = preempt_count();
 
-       entry->idx              = atomic_inc_return(&tracer_counter);
        entry->preempt_count    = pc & 0xff;
        entry->pid              = tsk->pid;
        entry->t                = ftrace_now(raw_smp_processor_id());
@@ -757,8 +755,10 @@ find_next_entry(struct trace_iterator *iter, int *ent_cpu)
                if (!head_page(tr->data[cpu]))
                        continue;
                ent = trace_entry_idx(tr, tr->data[cpu], iter, cpu);
-               if (ent &&
-                   (!next || (long)(next->idx - ent->idx) > 0)) {
+               /*
+                * Pick the entry with the smallest timestamp:
+                */
+               if (ent && (!next || ent->t < next->t)) {
                        next = ent;
                        next_cpu = cpu;
                }
@@ -800,8 +800,6 @@ trace_consume(struct trace_iterator *iter)
        if (data->trace_head == data->trace_tail &&
            data->trace_head_idx == data->trace_tail_idx)
                data->trace_idx = 0;
-
-       trace_iterator_increment(iter);
 }
 
 static notrace void *
@@ -1160,33 +1158,6 @@ print_lat_fmt(struct trace_iterator *iter, unsigned int trace_idx, int cpu)
        }
 }
 
-static notrace void sync_time_offset(struct trace_iterator *iter)
-{
-       struct trace_array_cpu *prev_array, *array;
-       struct trace_entry *prev_entry, *entry;
-       cycle_t prev_t, t;
-
-       entry = iter->ent;
-       prev_entry = iter->prev_ent;
-       if (!prev_entry)
-               return;
-
-       prev_array = iter->tr->data[iter->prev_cpu];
-       array = iter->tr->data[iter->cpu];
-
-       prev_t = prev_entry->t + prev_array->time_offset;
-       t = entry->t + array->time_offset;
-
-       /*
-        * If time goes backwards we increase the offset of
-        * the current array, to not have observable time warps.
-        * This will quickly synchronize the time offsets of
-        * multiple CPUs:
-        */
-       if (t < prev_t)
-               array->time_offset += prev_t - t;
-}
-
 static notrace int
 print_trace_fmt(struct trace_iterator *iter)
 {
@@ -1200,12 +1171,11 @@ print_trace_fmt(struct trace_iterator *iter)
        int S;
        int ret;
 
-       sync_time_offset(iter);
        entry = iter->ent;
 
        comm = trace_find_cmdline(iter->ent->pid);
 
-       t = ns2usecs(entry->t + iter->tr->data[iter->cpu]->time_offset);
+       t = ns2usecs(entry->t);
        usec_rem = do_div(t, 1000000ULL);
        secs = (unsigned long)t;
 

diff --git a/kernel/trace/trace.h b/kernel/trace/trace.h
index 30cad677e9d0bae2f25eddbcd2e489785cd70698..27fa2d06f499648c03441ba5a34cbc1fb94bf124 100644 (file)
--- a/kernel/trace/trace.h
+++ b/kernel/trace/trace.h
@@ -38,7 +38,6 @@ struct trace_entry {
        char                    preempt_count;
        int                     pid;
        cycle_t                 t;
-       unsigned long           idx;
        union {
                struct ftrace_entry             fn;
                struct ctx_switch_entry         ctx;
@@ -57,7 +56,6 @@ struct trace_array_cpu {
        atomic_t                disabled;
        spinlock_t              lock;
        struct lock_class_key   lock_key;
-       cycle_t                 time_offset;
 
        /* these fields get copied into max-trace: */
        unsigned                trace_head_idx;