From: Andrei Vagin <avagin@xxxxxxxxxx>
Subject: proc: optimize single-symbol delimiters to spead up seq_put_decimal_ull
A delimiter is a string which is printed before a number.
A syngle-symbol delimiters can be printed by set_putc() and this works
faster than printing by set_puts().
== test_proc.c
int main(int argc, char **argv)
{
int n, i, fd;
char buf[16384];
n = atoi(argv[1]);
for (i = 0; i < n; i++) {
fd = open(argv[2], O_RDONLY);
if (fd < 0)
return 1;
if (read(fd, buf, sizeof(buf)) <= 0)
return 1;
close(fd);
}
return 0;
}
==
$ time ./test_proc 1000000 /proc/1/stat
== Before patch ==
real 0m3.820s
user 0m0.337s
sys 0m3.394s
== After patch ==
real 0m3.110s
user 0m0.324s
sys 0m2.700s
Link: http://lkml.kernel.org/r/20180212074931.7227-3-avagin@xxxxxxxxxx
Signed-off-by: Andrei Vagin <avagin@xxxxxxxxxx>
Cc: Alexey Dobriyan <adobriyan@xxxxxxxxx>
Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@xxxxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
fs/seq_file.c | 24 ++++++++++++------------
1 file changed, 12 insertions(+), 12 deletions(-)
diff -puN fs/seq_file.c~proc-optimize-single-symbol-delimiters-to-spead-up-seq_put_decimal_ull fs/seq_file.c
--- a/fs/seq_file.c~proc-optimize-single-symbol-delimiters-to-spead-up-seq_put_decimal_ull
+++ a/fs/seq_file.c
@@ -693,12 +693,12 @@ void seq_put_decimal_ull_width(struct se
if (m->count + 2 >= m->size) /* we'll write 2 bytes at least */
goto overflow;
- len = strlen(delimiter);
- if (m->count + len >= m->size)
- goto overflow;
-
- memcpy(m->buf + m->count, delimiter, len);
- m->count += len;
+ if (delimiter && delimiter[0]) {
+ if (delimiter[1] == 0)
+ seq_putc(m, delimiter[0]);
+ else
+ seq_puts(m, delimiter);
+ }
if (!width)
width = 1;
@@ -782,12 +782,12 @@ void seq_put_decimal_ll(struct seq_file
if (m->count + 3 >= m->size) /* we'll write 2 bytes at least */
goto overflow;
- len = strlen(delimiter);
- if (m->count + len >= m->size)
- goto overflow;
-
- memcpy(m->buf + m->count, delimiter, len);
- m->count += len;
+ if (delimiter && delimiter[0]) {
+ if (delimiter[1] == 0)
+ seq_putc(m, delimiter[0]);
+ else
+ seq_puts(m, delimiter);
+ }
if (m->count + 2 >= m->size)
goto overflow;
_
--
To unsubscribe from this list: send the line "unsubscribe mm-commits" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
