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tracing: optimize trace_printk()

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Impact: micro-optimization

trace_printk() does this unconditionally:

	trace_printk_fmt = fmt;

Where trace_printk_fmt is an entry into a global array. This is
very SMP-unfriendly.

So only write it once per bootup.

Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Peter Zijlstra <peterz@infradead.org>
LKML-Reference: <1236356510-8381-5-git-send-email-fweisbec@gmail.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
This commit is contained in:
Ingo Molnar 2009-03-09 10:11:36 +01:00
parent 8a20d84d09
commit 7bffc23e56
1 changed files with 8 additions and 2 deletions
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6
include/linux/kernel.h
View file

@ -454,7 +454,10 @@ do { \
do { \
static const char *trace_printk_fmt \
__attribute__((section("__trace_printk_fmt"))); \
\
if (!trace_printk_fmt) \
trace_printk_fmt = fmt; \
\
__trace_printk_check_format(fmt, ##args); \
__trace_printk(_THIS_IP_, trace_printk_fmt, ##args); \
} while (0)
@ -467,7 +470,10 @@ __trace_printk(unsigned long ip, const char *fmt, ...)
do { \
static const char *trace_printk_fmt \
__attribute__((section("__trace_printk_fmt"))); \
\
if (!trace_printk_fmt) \
trace_printk_fmt = fmt; \
\
__ftrace_vprintk(_THIS_IP_, trace_printk_fmt, vargs); \
} while (0)