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Message-ID: <4B55607E.8070403@cn.fujitsu.com>
Date: Tue, 19 Jan 2010 15:34:22 +0800
From: Lai Jiangshan <laijs@...fujitsu.com>
To: Steven Rostedt <rostedt@...dmis.org>, linux-kernel@...r.kernel.org,
Ingo Molnar <mingo@...e.hu>,
Andrew Morton <akpm@...ux-foundation.org>,
Frederic Weisbecker <fweisbec@...il.com>
Subject: [PATCH 5/6] tracing: reduce latency and remove percpu trace_seq
__print_flags() and __print_symbolic() use percpu trace_seq:
1) Its memory is preallocated, it wastes memory when we don't use tracing.
2) It wastes memory for multi-cpus system.
3) It disables preemption when it executes its core routine
"trace_seq_printf(s, "%s: ", #call);" and introduce latency
for more important process.
So we move this trace_seq to struct trace_iterator.
Signed-off-by: Lai Jiangshan <laijs@...fujitsu.com>
---
diff --git a/include/linux/ftrace_event.h b/include/linux/ftrace_event.h
index be9ece5..348500d 100644
--- a/include/linux/ftrace_event.h
+++ b/include/linux/ftrace_event.h
@@ -12,9 +12,6 @@ struct dentry;
#define FTRACE_SEQ_BUFSIZE PAGE_SIZE
-DECLARE_PER_CPU(struct trace_seq, ftrace_event_seq);
-DECLARE_PER_CPU(unsigned char[FTRACE_SEQ_BUFSIZE], ftrace_event_buffer);
-
struct trace_print_flags {
unsigned long mask;
const char *name;
@@ -60,6 +57,10 @@ struct trace_iterator {
struct trace_seq seq;
unsigned char buffer[FTRACE_SEQ_BUFSIZE];
+ /* trace_seq for __print_flags() and __print_symbolic() */
+ struct trace_seq tmp_seq;
+ unsigned char tmp_buffer[FTRACE_SEQ_BUFSIZE];
+
struct trace_entry *ent;
int leftover;
int cpu;
diff --git a/include/trace/ftrace.h b/include/trace/ftrace.h
index f30f4d6..4807d1e 100644
--- a/include/trace/ftrace.h
+++ b/include/trace/ftrace.h
@@ -141,8 +141,7 @@
* struct trace_seq *s = &iter->seq;
* struct ftrace_raw_<call> *field; <-- defined in stage 1
* struct trace_entry *entry;
- * struct trace_seq *p;
- * unsigned char *buffer;
+ * struct trace_seq *p = &iter->tmp_seq;
* int ret;
*
* entry = iter->ent;
@@ -154,11 +153,8 @@
*
* field = (typeof(field))entry;
*
- * p = get_cpu_var(ftrace_event_seq);
- * buffer = get_cpu_var(ftrace_event_buffer);
- * trace_seq_init(p, buffer, FTRACE_SEQ_BUFSIZE);
+ * trace_seq_init(p, iter->tmp_buffer, FTRACE_SEQ_BUFSIZE);
* ret = trace_seq_printf(s, <TP_printk> "\n");
- * put_cpu();
* if (!ret)
* return TRACE_TYPE_PARTIAL_LINE;
*
@@ -208,10 +204,8 @@ ftrace_raw_output_id_##call(int event_id, const char *name, \
struct trace_seq *s = &iter->seq; \
struct ftrace_raw_##call *field; \
struct trace_entry *entry; \
- struct trace_seq *p; \
- unsigned char *buffer; \
+ struct trace_seq *p = &iter->tmp_seq; \
int ret; \
- int cpu; \
\
entry = iter->ent; \
\
@@ -222,14 +216,10 @@ ftrace_raw_output_id_##call(int event_id, const char *name, \
\
field = (typeof(field))entry; \
\
- cpu = get_cpu(); \
- p = &per_cpu(ftrace_event_seq, cpu); \
- buffer = per_cpu(ftrace_event_buffer, cpu); \
- trace_seq_init(p, buffer, FTRACE_SEQ_BUFSIZE); \
+ trace_seq_init(p, iter->tmp_buffer, FTRACE_SEQ_BUFSIZE); \
ret = trace_seq_printf(s, "%s: ", name); \
if (ret) \
ret = trace_seq_printf(s, print); \
- put_cpu(); \
if (!ret) \
return TRACE_TYPE_PARTIAL_LINE; \
\
@@ -253,10 +243,8 @@ 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; \
- unsigned char *buffer; \
+ struct trace_seq *p = &iter->tmp_seq; \
int ret; \
- int cpu; \
\
entry = iter->ent; \
\
@@ -267,14 +255,10 @@ ftrace_raw_output_##call(struct trace_iterator *iter, int flags) \
\
field = (typeof(field))entry; \
\
- cpu = get_cpu(); \
- p = &per_cpu(ftrace_event_seq, cpu); \
- buffer = per_cpu(ftrace_event_buffer, cpu); \
trace_seq_init(p, buffer, FTRACE_SEQ_BUFSIZE); \
ret = trace_seq_printf(s, "%s: ", #call); \
if (ret) \
ret = trace_seq_printf(s, print); \
- put_cpu(); \
if (!ret) \
return TRACE_TYPE_PARTIAL_LINE; \
\
diff --git a/kernel/trace/trace_output.c b/kernel/trace/trace_output.c
index 78f9825..f531a16 100644
--- a/kernel/trace/trace_output.c
+++ b/kernel/trace/trace_output.c
@@ -16,11 +16,6 @@
DECLARE_RWSEM(trace_event_mutex);
-DEFINE_PER_CPU(struct trace_seq, ftrace_event_seq);
-DEFINE_PER_CPU(unsigned char[PAGE_SIZE], ftrace_event_buffer);
-EXPORT_PER_CPU_SYMBOL(ftrace_event_seq);
-EXPORT_PER_CPU_SYMBOL(ftrace_event_buffer);
-
static struct hlist_head event_hash[EVENT_HASHSIZE] __read_mostly;
static int next_event_type = __TRACE_LAST_TYPE + 1;
--
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