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ftrace: remove-idx-sync

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remove idx syncing - it's expensive on SMP.

Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
This commit is contained in:
Ingo Molnar 2008-05-12 21:20:46 +02:00 committed by Thomas Gleixner
parent 53c37c17aa
commit cdd31cd2d7
2 changed files with 5 additions and 37 deletions
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40
kernel/trace/trace.c
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@ -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;

2
kernel/trace/trace.h
View File

@ -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;