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| author | Ingo Molnar <mingo@elte.hu> | 2009-03-09 10:11:36 +0100 |
|---|---|---|
| committer | Ingo Molnar <mingo@elte.hu> | 2009-03-09 10:11:36 +0100 |
| commit | 7bffc23e56e92c14b787bf4d95249a32085bfed5 (patch) | |
| tree | 9c1bbea2f258c82b5a9ff5e30db3a8f0c9cc3faa /include/linux/kernel.h | |
| parent | 8a20d84d09ab5d121f989cd99e4fc5f4b49f98ba (diff) | |
| download | lwn-7bffc23e56e92c14b787bf4d95249a32085bfed5.tar.gz lwn-7bffc23e56e92c14b787bf4d95249a32085bfed5.zip | |
tracing: optimize trace_printk()
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>
Diffstat (limited to 'include/linux/kernel.h')
| -rw-r--r-- | include/linux/kernel.h | 10 |
1 files changed, 8 insertions, 2 deletions
diff --git a/include/linux/kernel.h b/include/linux/kernel.h index 4e726b9a71ec..7742798c9208 100644 --- a/include/linux/kernel.h +++ b/include/linux/kernel.h @@ -454,7 +454,10 @@ do { \ do { \ static const char *trace_printk_fmt \ __attribute__((section("__trace_printk_fmt"))); \ - trace_printk_fmt = 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"))); \ - trace_printk_fmt = fmt; \ + \ + if (!trace_printk_fmt) \ + trace_printk_fmt = fmt; \ + \ __ftrace_vprintk(_THIS_IP_, trace_printk_fmt, vargs); \ } while (0) |