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basic: use _unlocked() stdio in strip_tab_ansi() (#6385)

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Trivial performance boost by explicitly bypassing the implicit
locking of stdio.

This significantly affects common cases of `journalctl` usage:

 Before:

  # time ./journalctl -b -1 > /dev/null
   real    0m26.628s
   user    0m26.495s
   sys     0m0.125s

  # time ./journalctl -b -1 > /dev/null
   real    0m27.069s
   user    0m26.936s
   sys     0m0.134s

  # time ./journalctl -b -1 > /dev/null
   real    0m26.727s
   user    0m26.607s
   sys     0m0.119s

 After:

  # time ./journalctl -b -1 > /dev/null
   real    0m23.394s
   user    0m23.244s
   sys     0m0.142s

  # time ./journalctl -b -1 > /dev/null
   real    0m23.283s
   user    0m23.160s
   sys     0m0.121s

  # time ./journalctl -b -1 > /dev/null
   real    0m23.274s
   user    0m23.125s
   sys     0m0.144s

Fixes https://github.com/systemd/systemd/issues/6341
This commit is contained in:
Vito Caputo
2017-07-18 00:05:52 +02:00
committed by Lennart Poettering
parent e758bc9132
commit db3f45e2d2
1 changed files with 12 additions and 7 deletions
Download Patch File Download Diff File Expand all files Collapse all files
src/basic/string-util.c
+12 -7
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@@ -635,6 +635,11 @@ char *strip_tab_ansi(char **ibuf, size_t *_isz) {
if (!f)
return NULL;
/* Note we use the _unlocked() stdio variants on f for performance
* reasons. It's safe to do so since we created f here and it
* doesn't leave our scope.
*/
for (i = *ibuf; i < *ibuf + isz + 1; i++) {
switch (state) {
@@ -645,21 +650,21 @@ char *strip_tab_ansi(char **ibuf, size_t *_isz) {
else if (*i == '\x1B')
state = STATE_ESCAPE;
else if (*i == '\t')
fputs(" ", f);
fputs_unlocked(" ", f);
else
fputc(*i, f);
fputc_unlocked(*i, f);
break;
case STATE_ESCAPE:
if (i >= *ibuf + isz) { /* EOT */
fputc('\x1B', f);
fputc_unlocked('\x1B', f);
break;
} else if (*i == '[') {
state = STATE_BRACKET;
begin = i + 1;
} else {
fputc('\x1B', f);
fputc(*i, f);
fputc_unlocked('\x1B', f);
fputc_unlocked(*i, f);
state = STATE_OTHER;
}
@@ -669,8 +674,8 @@ char *strip_tab_ansi(char **ibuf, size_t *_isz) {
if (i >= *ibuf + isz || /* EOT */
(!(*i >= '0' && *i <= '9') && *i != ';' && *i != 'm')) {
fputc('\x1B', f);
fputc('[', f);
fputc_unlocked('\x1B', f);
fputc_unlocked('[', f);
state = STATE_OTHER;
i = begin-1;
} else if (*i == 'm')