AcoSail/kernel_optimize_test
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tracing: Reduce latency and remove percpu trace_seq

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__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>
This commit is contained in:
Lai Jiangshan 2010-06-03 18:26:24 +08:00 committed by Steven Rostedt
parent 985023dee6
commit bc289ae98b
3 changed files with 6 additions and 14 deletions
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5
include/linux/ftrace_event.h
View File

@ -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;

12
include/trace/ftrace.h
View File

@ -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; \
\

3
kernel/trace/trace_output.c
View File

@ -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;