Messages in this thread Patch in this message |  | | Date | Mon, 30 Jan 2012 15:20:51 -0800 | From | Andrew Morton <> | Subject | Re: [PATCH] Add num_to_str() for speedup /proc/stat |
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On Mon, 30 Jan 2012 14:16:19 +0900 KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com> wrote:
> From: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com> > Date: Mon, 30 Jan 2012 14:15:12 +0900 > Subject: [PATCH] Add num_to_str() for speedup /proc/stat > > At reading /proc/stat, most of time is consumed by vsnprintf() at el. > > Here is a test script, reading /proc/stat 1000 times.. > > == 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 > > Maybe it's worth to add this simple function.
I suppose so - the new infrastructure can be used elsewhere.
I tried doing the
if (kstst_irqs(j) == 0) { seq_putc(p, ' '); seq_putc(p, '0');
think on top of this and didn't observe any improvement.
I made some changes - please review. I'm not sure why you did "char tmp[66]"?
From: Andrew Morton <akpm@linux-foundation.org> Subject: procfs-add-num_to_str-to-speed-up-proc-stat-fix
- remove incorrect comment - use less stack in num_to_str() - move comment from .h to .c - simplify seq_put_decimal_ull()
Cc: Eric Dumazet <eric.dumazet@gmail.com> Cc: Glauber Costa <glommer@parallels.com> Cc: Ingo Molnar <mingo@elte.hu> Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com> Cc: Paul Turner <pjt@google.com> Cc: Peter Zijlstra <a.p.zijlstra@chello.nl> Cc: Russell King <rmk@arm.linux.org.uk> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> ---
fs/seq_file.c | 5 ++--- include/linux/kernel.h | 6 ------ include/linux/seq_file.h | 4 +--- lib/vsprintf.c | 8 +++++++- 4 files changed, 10 insertions(+), 13 deletions(-)
diff -puN fs/proc/stat.c~procfs-add-num_to_str-to-speed-up-proc-stat-fix fs/proc/stat.c diff -puN fs/seq_file.c~procfs-add-num_to_str-to-speed-up-proc-stat-fix fs/seq_file.c --- a/fs/seq_file.c~procfs-add-num_to_str-to-speed-up-proc-stat-fix +++ a/fs/seq_file.c @@ -659,14 +659,13 @@ int seq_put_decimal_ull(struct seq_file if (m->count + 2 >= m->size) /* we'll write 2 bytes at least */ goto overflow; + m->buf[m->count++] = delimiter; + if (num < 10) { - m->buf[m->count++] = delimiter; m->buf[m->count++] = num + '0'; return 0; } - m->buf[m->count++] = delimiter; - len = num_to_str(m->buf + m->count, m->size - m->count, num); if (!len) goto overflow; diff -puN include/linux/kernel.h~procfs-add-num_to_str-to-speed-up-proc-stat-fix include/linux/kernel.h --- a/include/linux/kernel.h~procfs-add-num_to_str-to-speed-up-proc-stat-fix +++ a/include/linux/kernel.h @@ -299,12 +299,6 @@ extern long long simple_strtoll(const ch #define strict_strtoull kstrtoull #define strict_strtoll kstrtoll -/* - * Convert passed number to decimal string. - * returns returns the length of string. at buffer overflow, returns 0. - * - * If speed is not important, use snprintf(). It's easy to read the code. - */ extern int num_to_str(char *buf, int size, unsigned long long num); /* lib/printf utilities */ diff -puN include/linux/seq_file.h~procfs-add-num_to_str-to-speed-up-proc-stat-fix include/linux/seq_file.h --- a/include/linux/seq_file.h~procfs-add-num_to_str-to-speed-up-proc-stat-fix +++ a/include/linux/seq_file.h @@ -121,10 +121,8 @@ int single_release(struct inode *, struc 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 *); - -/* defined in lib/vsprintf.c */ int seq_put_decimal_ull(struct seq_file *m, char delimiter, - unsigned long long num); + unsigned long long num); #define SEQ_START_TOKEN ((void *)1) /* diff -puN lib/vsprintf.c~procfs-add-num_to_str-to-speed-up-proc-stat-fix lib/vsprintf.c --- a/lib/vsprintf.c~procfs-add-num_to_str-to-speed-up-proc-stat-fix +++ a/lib/vsprintf.c @@ -212,9 +212,15 @@ char *put_dec(char *buf, unsigned long l } } +/* + * Convert passed number to decimal string. + * Returns the length of string. On buffer overflow, returns 0. + * + * If speed is not important, use snprintf(). It's easy to read the code. + */ int num_to_str(char *buf, int size, unsigned long long num) { - char tmp[66]; + char tmp[21]; /* Enough for 2^64 in decimal */ int idx, len; len = put_dec(tmp, num) - tmp; _
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