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authorKAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>2012-03-24 02:02:54 +0400
committerLinus Torvalds <torvalds@linux-foundation.org>2012-03-24 03:58:42 +0400
commit1ac101a5d675aca2426c5cd460c73fb95acb8391 (patch)
tree5d993fde0c5e67de97c0d9ffac54163f06fc90c9 /include/linux/seq_file.h
parent59a32e2ce5eb809967cac4e718bc527beca83c59 (diff)
downloadlinux-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/seq_file.h')
-rw-r--r--include/linux/seq_file.h3
1 files changed, 2 insertions, 1 deletions
diff --git a/include/linux/seq_file.h b/include/linux/seq_file.h
index 44f1514b00ba..5bba42c99448 100644
--- a/include/linux/seq_file.h
+++ b/include/linux/seq_file.h
@@ -121,9 +121,10 @@ int single_release(struct inode *, struct file *);
void *__seq_open_private(struct file *, const struct seq_operations *, int);
int seq_open_private(struct file *, const struct seq_operations *, int);
int seq_release_private(struct inode *, struct file *);
+int seq_put_decimal_ull(struct seq_file *m, char delimiter,
+ unsigned long long num);
#define SEQ_START_TOKEN ((void *)1)
-
/*
* Helpers for iteration over list_head-s in seq_files
*/