tracing: Consolidate max_tr into main trace_array structure

Currently, the way the latency tracers and snapshot feature works
is to have a separate trace_array called "max_tr" that holds the
snapshot buffer. For latency tracers, this snapshot buffer is used
to swap the running buffer with this buffer to save the current max
latency.

The only items needed for the max_tr is really just a copy of the buffer
itself, the per_cpu data pointers, the time_start timestamp that states
when the max latency was triggered, and the cpu that the max latency
was triggered on. All other fields in trace_array are unused by the
max_tr, making the max_tr mostly bloat.

This change removes the max_tr completely, and adds a new structure
called trace_buffer, that holds the buffer pointer, the per_cpu data
pointers, the time_start timestamp, and the cpu where the latency occurred.

The trace_array, now has two trace_buffers, one for the normal trace and
one for the max trace or snapshot. By doing this, not only do we remove
the bloat from the max_trace but the instances of traces can now use
their own snapshot feature and not have just the top level global_trace have
the snapshot feature and latency tracers for itself.

Signed-off-by: Steven Rostedt <rostedt@goodmis.org>

1 files changed, 4 insertions, 4 deletions

diff --git a/kernel/trace/trace_sched_switch.c b/kernel/trace/trace_sched_switch.c
index 1ffe39abd6fc..4e98e3b257a3 100644
--- a/kernel/trace/trace_sched_switch.c
+++ b/kernel/trace/trace_sched_switch.c
@@ -28,7 +28,7 @@ tracing_sched_switch_trace(struct trace_array *tr,
                            unsigned long flags, int pc)
 {
         struct ftrace_event_call *call = &event_context_switch;
-        struct ring_buffer *buffer = tr->buffer;
+        struct ring_buffer *buffer = tr->trace_buffer.buffer;
         struct ring_buffer_event *event;
         struct ctx_switch_entry *entry;
 
@@ -69,7 +69,7 @@ probe_sched_switch(void *ignore, struct task_struct *prev, struct task_struct *n
         pc = preempt_count();
         local_irq_save(flags);
         cpu = raw_smp_processor_id();
-        data = per_cpu_ptr(ctx_trace->data, cpu);
+        data = per_cpu_ptr(ctx_trace->trace_buffer.data, cpu);
 
         if (likely(!atomic_read(&data->disabled)))
                 tracing_sched_switch_trace(ctx_trace, prev, next, flags, pc);
@@ -86,7 +86,7 @@ tracing_sched_wakeup_trace(struct trace_array *tr,
         struct ftrace_event_call *call = &event_wakeup;
         struct ring_buffer_event *event;
         struct ctx_switch_entry *entry;
-        struct ring_buffer *buffer = tr->buffer;
+        struct ring_buffer *buffer = tr->trace_buffer.buffer;
 
         event = trace_buffer_lock_reserve(buffer, TRACE_WAKE,
                                           sizeof(*entry), flags, pc);
@@ -123,7 +123,7 @@ probe_sched_wakeup(void *ignore, struct task_struct *wakee, int success)
         pc = preempt_count();
         local_irq_save(flags);
         cpu = raw_smp_processor_id();
-        data = per_cpu_ptr(ctx_trace->data, cpu);
+        data = per_cpu_ptr(ctx_trace->trace_buffer.data, cpu);
 
         if (likely(!atomic_read(&data->disabled)))
                 tracing_sched_wakeup_trace(ctx_trace, wakee, current,