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This patch cleans up the strsep implementation and improves performance.

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Currently strsep calls strpbrk is is now a veneer to strcspn.  Calling
strcspn directly is faster.  Since it handles a delimiter string of size
1 as a special case, this is not needed in strsep itself.  Although this
means there is a slightly higher overhead if the delimiter size is 1,
all other cases are slightly faster.  The overall performance gain is 5-10%
on AArch64.

The string/bits/string2.h header contains optimizations for constant
delimiters of size 1-3.  Benchmarking these showed similar performance for
size 1 (since in all cases strchr/strchrnul is used), while size 2 and 3
can give up to 2x speedup for small input strings.  However if these cases
are common it seems much better to add this optimization to strcspn.
So move these header optimizations to string-inlines.c.

Improve the strsep benchmark so that it actually benchmarks something.
The current version contains a delimiter character at every position in the
input string, so there is very little work to do, and the extremely inefficent
simple_strsep implementation appears fastest in every case.  The new version
has either no match in the input for the fail case and a match halfway in the
input for the success case.  The input is then restored so that each iteration
does exactly the same amount of work.  Reduce the number of testcases since
simple_strsep takes a lot of time now.

	* benchtests/bench-strsep.c (oldstrsep): Add old implementation.
	(do_one_test) Restore original string so iteration works.
	* string/string-inlines.c (do_test): Create better input strings.
	(test_main) Reduce number of testruns.
	* string/string-inlines.c (__old_strsep_1c): New function.
	(__old_strsep_2c): Likewise.
	(__old_strsep_3c): Likewise.
	* string/strsep.c (__strsep): Remove case of small delim string.
	Call strcspn directly rather than strpbrk.
	* string/bits/string2.h (__strsep): Remove define.
	(__strsep_1c): Remove.
	(__strsep_2c): Remove.
	(__strsep_3c): Remove.
	(strsep): Remove.
	* sysdeps/unix/sysv/linux/internal_statvfs.c
	(__statvfs_getflags): Rename to __strsep.
This commit is contained in:
Wilco Dijkstra 2016-12-21 15:16:29 +00:00
parent d08ab9ced7
commit 5625f666ce
6 changed files with 145 additions and 135 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

19
ChangeLog
View File

@ -1,3 +1,22 @@
2015-12-21 Wilco Dijkstra <wdijkstr@arm.com>
* benchtests/bench-strsep.c (oldstrsep): Add old implementation.
(do_one_test) Restore original string so iteration works.
* string/string-inlines.c (do_test): Create better input strings.
(test_main) Reduce number of testruns.
* string/string-inlines.c (__old_strsep_1c): New function.
(__old_strsep_2c): Likewise.
(__old_strsep_3c): Likewise.
* string/strsep.c (__strsep): Remove case of small delim string.
Call strcspn directly rather than strpbrk.
* string/bits/string2.h (__strsep): Remove define.
(__strsep_1c): Remove.
(__strsep_2c): Remove.
(__strsep_3c): Remove.
(strsep): Remove.
* sysdeps/unix/sysv/linux/internal_statvfs.c
(__statvfs_getflags): Rename to __strsep.
2016-12-21 Florian Weimer <fweimer@redhat.com>
* csu/libc-tls.c (_dl_tls_setup): Remove.

77
benchtests/bench-strsep.c
View File

@ -49,10 +49,56 @@ simple_strsep (char **s1, char *s2)
return begin;
}
char *
oldstrsep (char **stringp, const char *delim)
{
char *begin, *end;
begin = *stringp;
if (begin == NULL)
return NULL;
/* A frequent case is when the delimiter string contains only one
character. Here we don't need to call the expensive `strpbrk'
function and instead work using `strchr'. */
if (delim[0] == '\0' || delim[1] == '\0')
{
char ch = delim[0];
if (ch == '\0')
end = NULL;
else
{
if (*begin == ch)
end = begin;
else if (*begin == '\0')
end = NULL;
else
end = strchr (begin + 1, ch);
}
}
else
/* Find the end of the token. */
end = strpbrk (begin, delim);
if (end)
{
/* Terminate the token and set *STRINGP past NUL character. */
*end++ = '\0';
*stringp = end;
}
else
/* No more delimiters; this is the last token. */
*stringp = NULL;
return begin;
}
typedef char *(*proto_t) (const char **, const char *);
IMPL (simple_strsep, 0)
IMPL (strsep, 1)
IMPL (oldstrsep, 2)
static void
do_one_test (impl_t * impl, const char *s1, const char *s2)
@ -63,7 +109,10 @@ do_one_test (impl_t * impl, const char *s1, const char *s2)
TIMING_NOW (start);
for (i = 0; i < iters; ++i)
{
CALL (impl, &s1, s2);
const char *s1a = s1;
CALL (impl, &s1a, s2);
if (s1a != NULL)
((char*)s1a)[-1] = '1';
}
TIMING_NOW (stop);
@ -76,7 +125,10 @@ static void
do_test (size_t align1, size_t align2, size_t len1, size_t len2, int fail)
{
char *s2 = (char *) (buf2 + align2);
static const char d[] = "1234567890abcdef";
/* Search for a delimiter in a string containing mostly '0', so don't
use '0' as a delimiter. */
static const char d[] = "123456789abcdefg";
#define dl (sizeof (d) - 1)
char *ss2 = s2;
for (size_t l = len2; l > 0; l = l > dl ? l - dl : 0)
@ -92,24 +144,9 @@ do_test (size_t align1, size_t align2, size_t len1, size_t len2, int fail)
FOR_EACH_IMPL (impl, 0)
{
char *s1 = (char *) (buf1 + align1);
if (fail)
{
char *ss1 = s1;
for (size_t l = len1; l > 0; l = l > dl ? l - dl : 0)
{
size_t t = l > dl ? dl : l;
memcpy (ss1, d, t);
++ss1[len2 > 7 ? 7 : len2 - 1];
ss1 += t;
}
}
else
{
memset (s1, '0', len1);
memcpy (s1 + (len1 - len2) - 2, s2, len2);
if ((len1 / len2) > 4)
memcpy (s1 + (len1 - len2) - (3 * len2), s2, len2);
}
if (!fail)
s1[len1 / 2] = '1';
s1[len1] = '\0';
do_one_test (impl, s1, s2);
}
@ -127,7 +164,7 @@ test_main (void)
putchar ('\n');
for (size_t klen = 2; klen < 32; ++klen)
for (size_t hlen = 2 * klen; hlen < 16 * klen; hlen += klen)
for (size_t hlen = 4 * klen; hlen < 8 * klen; hlen += klen)
{
do_test (0, 0, hlen, klen, 0);
do_test (0, 0, hlen, klen, 1);

90
string/bits/string2.h
View File

@ -180,96 +180,6 @@ extern void *__rawmemchr (const void *__s, int __c);
#endif
#if !defined _HAVE_STRING_ARCH_strsep || defined _FORCE_INLINES
# ifndef _HAVE_STRING_ARCH_strsep
extern char *__strsep_g (char **__stringp, const char *__delim);
# define __strsep(s, reject) \
__extension__ \
({ char __r0, __r1, __r2; \
(__builtin_constant_p (reject) && __string2_1bptr_p (reject) \
&& (__r0 = ((const char *) (reject))[0], \
((const char *) (reject))[0] != '\0') \
? ((__r1 = ((const char *) (reject))[1], \
((const char *) (reject))[1] == '\0') \
? __strsep_1c (s, __r0) \
: ((__r2 = ((const char *) (reject))[2], __r2 == '\0') \
? __strsep_2c (s, __r0, __r1) \
: (((const char *) (reject))[3] == '\0' \
? __strsep_3c (s, __r0, __r1, __r2) \
: __strsep_g (s, reject)))) \
: __strsep_g (s, reject)); })
# endif
__STRING_INLINE char *__strsep_1c (char **__s, char __reject);
__STRING_INLINE char *
__strsep_1c (char **__s, char __reject)
{
char *__retval = *__s;
if (__retval != NULL && (*__s = strchr (__retval, __reject)) != NULL)
*(*__s)++ = '\0';
return __retval;
}
__STRING_INLINE char *__strsep_2c (char **__s, char __reject1, char __reject2);
__STRING_INLINE char *
__strsep_2c (char **__s, char __reject1, char __reject2)
{
char *__retval = *__s;
if (__retval != NULL)
{
char *__cp = __retval;
while (1)
{
if (*__cp == '\0')
{
__cp = NULL;
break;
}
if (*__cp == __reject1 || *__cp == __reject2)
{
*__cp++ = '\0';
break;
}
++__cp;
}
*__s = __cp;
}
return __retval;
}
__STRING_INLINE char *__strsep_3c (char **__s, char __reject1, char __reject2,
char __reject3);
__STRING_INLINE char *
__strsep_3c (char **__s, char __reject1, char __reject2, char __reject3)
{
char *__retval = *__s;
if (__retval != NULL)
{
char *__cp = __retval;
while (1)
{
if (*__cp == '\0')
{
__cp = NULL;
break;
}
if (*__cp == __reject1 || *__cp == __reject2 || *__cp == __reject3)
{
*__cp++ = '\0';
break;
}
++__cp;
}
*__s = __cp;
}
return __retval;
}
# ifdef __USE_MISC
# define strsep(s, reject) __strsep (s, reject)
# endif
#endif
/* We need the memory allocation functions for inline strdup().
Referring to stdlib.h (even minimally) is not allowed
in any of the tight standards compliant modes. */

64
string/string-inlines.c
View File

@ -63,6 +63,70 @@ __old_strtok_r_1c (char *__s, char __sep, char **__nextp)
return __result;
}
compat_symbol (libc, __old_strtok_r_1c, __strtok_r_1c, GLIBC_2_1_1);
char *
__old_strsep_1c (char **__s, char __reject)
{
char *__retval = *__s;
if (__retval != NULL && (*__s = strchr (__retval, __reject)) != NULL)
*(*__s)++ = '\0';
return __retval;
}
compat_symbol (libc, __old_strsep_1c, __strsep_1c, GLIBC_2_1_1);
char *
__old_strsep_2c (char **__s, char __reject1, char __reject2)
{
char *__retval = *__s;
if (__retval != NULL)
{
char *__cp = __retval;
while (1)
{
if (*__cp == '\0')
{
__cp = NULL;
break;
}
if (*__cp == __reject1 || *__cp == __reject2)
{
*__cp++ = '\0';
break;
}
++__cp;
}
*__s = __cp;
}
return __retval;
}
compat_symbol (libc, __old_strsep_2c, __strsep_2c, GLIBC_2_1_1);
char *
__old_strsep_3c (char **__s, char __reject1, char __reject2, char __reject3)
{
char *__retval = *__s;
if (__retval != NULL)
{
char *__cp = __retval;
while (1)
{
if (*__cp == '\0')
{
__cp = NULL;
break;
}
if (*__cp == __reject1 || *__cp == __reject2 || *__cp == __reject3)
{
*__cp++ = '\0';
break;
}
++__cp;
}
*__s = __cp;
}
return __retval;
}
compat_symbol (libc, __old_strsep_3c, __strsep_3c, GLIBC_2_1_1);
#endif
#if SHLIB_COMPAT (libc, GLIBC_2_1_1, GLIBC_2_24)

24
string/strsep.c
View File

@ -29,30 +29,10 @@ __strsep (char **stringp, const char *delim)
if (begin == NULL)
return NULL;
/* A frequent case is when the delimiter string contains only one
character. Here we don't need to call the expensive `strpbrk'
function and instead work using `strchr'. */
if (delim[0] == '\0' || delim[1] == '\0')
{
char ch = delim[0];
if (ch == '\0')
end = NULL;
else
{
if (*begin == ch)
end = begin;
else if (*begin == '\0')
end = NULL;
else
end = strchr (begin + 1, ch);
}
}
else
/* Find the end of the token. */
end = strpbrk (begin, delim);
end = begin + strcspn (begin, delim);
if (end)
if (*end)
{
/* Terminate the token and set *STRINGP past NUL character. */
*end++ = '\0';

2
sysdeps/unix/sysv/linux/internal_statvfs.c
View File

@ -168,7 +168,7 @@ __statvfs_getflags (const char *name, int fstype, int fd)
char *cp = mntbuf.mnt_opts;
char *opt;
while ((opt = strsep (&cp, ",")) != NULL)
while ((opt = __strsep (&cp, ",")) != NULL)
if (strcmp (opt, "ro") == 0)
result |= ST_RDONLY;
else if (strcmp (opt, "nosuid") == 0)