tracing: Reduce latency and remove percpu trace_seq

__print_flags() and __print_symbolic() use percpu trace_seq:

1) Its memory is allocated at compile time, it wastes memory if we don't use tracing.
2) It is percpu data and it wastes more memory for multi-cpus system.
3) It disables preemption when it executes its core routine
   "trace_seq_printf(s, "%s: ", #call);" and introduces latency.

So we move this trace_seq to struct trace_iterator.

Signed-off-by: Lai Jiangshan <laijs@cn.fujitsu.com>
LKML-Reference: <4C078350.7090106@cn.fujitsu.com>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>

1 files changed, 3 insertions, 2 deletions

diff --git a/include/linux/ftrace_event.h b/include/linux/ftrace_event.h
index 2b7b1395b4d5..02b8b24f8f51 100644
--- a/include/linux/ftrace_event.h
+++ b/include/linux/ftrace_event.h
@@ -11,8 +11,6 @@ struct trace_array;
 struct tracer;
 struct dentry;
 
-DECLARE_PER_CPU(struct trace_seq, ftrace_event_seq);
-
 struct trace_print_flags {
         unsigned long           mask;
         const char              *name;
@@ -58,6 +56,9 @@ struct trace_iterator {
         struct ring_buffer_iter *buffer_iter[NR_CPUS];
         unsigned long           iter_flags;
 
+        /* trace_seq for __print_flags() and __print_symbolic() etc. */
+        struct trace_seq        tmp_seq;
+
         /* The below is zeroed out in pipe_read */
         struct trace_seq        seq;
         struct trace_entry      *ent;