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Commit bc289ae9 authored by Lai Jiangshan's avatar Lai Jiangshan Committed by Steven Rostedt
Browse files

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: default avatarLai Jiangshan <laijs@cn.fujitsu.com>
LKML-Reference: <4C078350.7090106@cn.fujitsu.com>
Signed-off-by: default avatarSteven Rostedt <rostedt@goodmis.org>
parent 985023de

include/linux/ftrace_event.h

+3 −2
Original line number Diff line number Diff line
@@ -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;

include/trace/ftrace.h

+3 −9
Original line number Diff line number Diff line
@@ -145,7 +145,7 @@ 
 *	struct trace_seq *s = &iter->seq;

 *	struct ftrace_raw_<call> *field; <-- defined in stage 1

 *	struct trace_entry *entry;

 *	struct trace_seq *p;

 *	struct trace_seq *p = &iter->tmp_seq;

 *	int ret;

 *

 *	entry = iter->ent;
@@ -157,12 +157,10 @@ 
 *

 *	field = (typeof(field))entry;

 *

 *	p = &get_cpu_var(ftrace_event_seq);

 *	trace_seq_init(p);

 *	ret = trace_seq_printf(s, "%s: ", <call>);

 *	if (ret)

 *		ret = trace_seq_printf(s, <TP_printk> "\n");

 *	put_cpu();

 *	if (!ret)

 *		return TRACE_TYPE_PARTIAL_LINE;

 *
@@ -216,7 +214,7 @@ ftrace_raw_output_##call(struct trace_iterator *iter, int flags, \ 
	struct trace_seq *s = &iter->seq;				\

	struct ftrace_raw_##call *field;				\

	struct trace_entry *entry;					\

	struct trace_seq *p;						\

	struct trace_seq *p = &iter->tmp_seq;				\

	int ret;							\

									\

	event = container_of(trace_event, struct ftrace_event_call,	\
@@ -231,12 +229,10 @@ ftrace_raw_output_##call(struct trace_iterator *iter, int flags, \ 
									\

	field = (typeof(field))entry;					\

									\

	p = &get_cpu_var(ftrace_event_seq);				\

	trace_seq_init(p);						\

	ret = trace_seq_printf(s, "%s: ", event->name);			\

	if (ret)							\

		ret = trace_seq_printf(s, print);			\

	put_cpu();							\

	if (!ret)							\

		return TRACE_TYPE_PARTIAL_LINE;				\

									\
@@ -255,7 +251,7 @@ ftrace_raw_output_##call(struct trace_iterator *iter, int flags, \ 
	struct trace_seq *s = &iter->seq;				\

	struct ftrace_raw_##template *field;				\

	struct trace_entry *entry;					\

	struct trace_seq *p;						\

	struct trace_seq *p = &iter->tmp_seq;				\

	int ret;							\

									\

	entry = iter->ent;						\
@@ -267,12 +263,10 @@ ftrace_raw_output_##call(struct trace_iterator *iter, int flags, \ 
									\

	field = (typeof(field))entry;					\

									\

	p = &get_cpu_var(ftrace_event_seq);				\

	trace_seq_init(p);						\

	ret = trace_seq_printf(s, "%s: ", #call);			\

	if (ret)							\

		ret = trace_seq_printf(s, print);			\

	put_cpu();							\

	if (!ret)							\

		return TRACE_TYPE_PARTIAL_LINE;				\

									\

kernel/trace/trace_output.c

+0 −3
Original line number Diff line number Diff line
@@ -16,9 +16,6 @@ 


DECLARE_RWSEM(trace_event_mutex);



DEFINE_PER_CPU(struct trace_seq, ftrace_event_seq);

EXPORT_PER_CPU_SYMBOL(ftrace_event_seq);



static struct hlist_head event_hash[EVENT_HASHSIZE] __read_mostly;



static int next_event_type = __TRACE_LAST_TYPE + 1;