diff options
| author | KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com> | 2012-03-24 02:02:54 +0400 |
|---|---|---|
| committer | Linus Torvalds <torvalds@linux-foundation.org> | 2012-03-24 03:58:42 +0400 |
| commit | 1ac101a5d675aca2426c5cd460c73fb95acb8391 (patch) | |
| tree | 5d993fde0c5e67de97c0d9ffac54163f06fc90c9 /include/linux/kernel.h | |
| parent | 59a32e2ce5eb809967cac4e718bc527beca83c59 (diff) | |
| download | linux-1ac101a5d675aca2426c5cd460c73fb95acb8391.tar.xz | |
procfs: add num_to_str() to speed up /proc/stat
== stat_check.py
num = 0
with open("/proc/stat") as f:
while num < 1000 :
data = f.read()
f.seek(0, 0)
num = num + 1
==
perf shows
20.39% stat_check.py [kernel.kallsyms] [k] format_decode
13.41% stat_check.py [kernel.kallsyms] [k] number
12.61% stat_check.py [kernel.kallsyms] [k] vsnprintf
10.85% stat_check.py [kernel.kallsyms] [k] memcpy
4.85% stat_check.py [kernel.kallsyms] [k] radix_tree_lookup
4.43% stat_check.py [kernel.kallsyms] [k] seq_printf
This patch removes most of calls to vsnprintf() by adding num_to_str()
and seq_print_decimal_ull(), which prints decimal numbers without rich
functions provided by printf().
On my 8cpu box.
== Before patch ==
[root@bluextal test]# time ./stat_check.py
real 0m0.150s
user 0m0.026s
sys 0m0.121s
== After patch ==
[root@bluextal test]# time ./stat_check.py
real 0m0.055s
user 0m0.022s
sys 0m0.030s
[akpm@linux-foundation.org: remove incorrect comment, use less statck in num_to_str(), move comment from .h to .c, simplify seq_put_decimal_ull()]
[andrea@betterlinux.com: avoid breaking the ABI in /proc/stat]
Signed-off-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Signed-off-by: Andrea Righi <andrea@betterlinux.com>
Cc: Eric Dumazet <eric.dumazet@gmail.com>
Cc: Glauber Costa <glommer@parallels.com>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Paul Turner <pjt@google.com>
Cc: Russell King <rmk@arm.linux.org.uk>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'include/linux/kernel.h')
| -rw-r--r-- | include/linux/kernel.h | 2 |
1 files changed, 2 insertions, 0 deletions
diff --git a/include/linux/kernel.h b/include/linux/kernel.h index f2085b541a24..3e140add5360 100644 --- a/include/linux/kernel.h +++ b/include/linux/kernel.h @@ -312,6 +312,8 @@ extern long long simple_strtoll(const char *,char **,unsigned int); #define strict_strtoull kstrtoull #define strict_strtoll kstrtoll +extern int num_to_str(char *buf, int size, unsigned long long num); + /* lib/printf utilities */ extern __printf(2, 3) int sprintf(char *buf, const char * fmt, ...); |