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MINOR: regex: use a thread-local match pointer for pcre2

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The pcre2 matching requires an array of matches for grouping, that is
allocated when executing the rule by pre-processing it, and that is
immediately freed after use. This is quite inefficient and results in
annoying patterns in "show profiling" that attribute the allocations
to libpcre2 and the releases to haproxy.

A good suggestion from Dragan is to pre-allocate these per thread,
since the entry is not specific to a regex. In addition we're already
limited to MAX_MATCH matches so we don't even have the problem of
having to grow it while parsing nor processing.

The current patch adds a per-thread pair of init/deinit functions to
allocate a thread-local entry for that, and gets rid of the dynamic
allocations. It will result in cleaner memory management patterns and
slightly higher performance (+2.5%) when using pcre2.
This commit is contained in:
Willy Tarreau 2025-10-13 16:47:50 +02:00
parent 6f4ca37880
commit fda6dc9597
2 changed files with 37 additions and 29 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

14
include/haproxy/regex.h
View File

@ -30,6 +30,10 @@
extern THREAD_LOCAL regmatch_t pmatch[MAX_MATCH];
#if defined(USE_PCRE2)
extern THREAD_LOCAL pcre2_match_data *local_pcre2_match;
#endif
/* "str" is the string that contain the regex to compile.
* "regex" is preallocated memory. After the execution of this function, this
* struct contain the compiled regex.
@ -58,13 +62,10 @@ static inline int regex_exec(const struct my_regex *preg, char *subject)
return 0;
return 1;
#elif defined(USE_PCRE2)
pcre2_match_data *pm;
int ret;
pm = pcre2_match_data_create_from_pattern(preg->reg, NULL);
ret = preg->mfn(preg->reg, (PCRE2_SPTR)subject, (PCRE2_SIZE)strlen(subject),
0, 0, pm, NULL);
pcre2_match_data_free(pm);
0, 0, local_pcre2_match, NULL);
if (ret < 0)
return 0;
return 1;
@ -90,13 +91,10 @@ static inline int regex_exec2(const struct my_regex *preg, char *subject, int le
return 0;
return 1;
#elif defined(USE_PCRE2)
pcre2_match_data *pm;
int ret;
pm = pcre2_match_data_create_from_pattern(preg->reg, NULL);
ret = preg->mfn(preg->reg, (PCRE2_SPTR)subject, (PCRE2_SIZE)length,
0, 0, pm, NULL);
pcre2_match_data_free(pm);
0, 0, local_pcre2_match, NULL);
if (ret < 0)
return 0;
return 1;

52
src/regex.c
View File

@ -23,6 +23,11 @@
/* regex trash buffer used by various regex tests */
THREAD_LOCAL regmatch_t pmatch[MAX_MATCH]; /* rm_so, rm_eo for regular expressions */
#if defined(USE_PCRE2)
/* avoid alloc/free cycles */
THREAD_LOCAL pcre2_match_data *local_pcre2_match = NULL;
#endif
int exp_replace(char *dst, unsigned int dst_size, char *src, const char *str, const regmatch_t *matches)
{
char *old_dst = dst;
@ -134,7 +139,6 @@ int regex_exec_match(const struct my_regex *preg, const char *subject,
int ret;
#ifdef USE_PCRE2
PCRE2_SIZE *matches;
pcre2_match_data *pm;
#else
int matches[MAX_MATCH * 3];
#endif
@ -169,15 +173,12 @@ int regex_exec_match(const struct my_regex *preg, const char *subject,
* space in the matches array.
*/
#ifdef USE_PCRE2
pm = pcre2_match_data_create_from_pattern(preg->reg, NULL);
ret = preg->mfn(preg->reg, (PCRE2_SPTR)subject, (PCRE2_SIZE)strlen(subject), 0, options, pm, NULL);
ret = preg->mfn(preg->reg, (PCRE2_SPTR)subject, (PCRE2_SIZE)strlen(subject), 0, options, local_pcre2_match, NULL);
if (ret < 0) {
pcre2_match_data_free(pm);
if (ret < 0)
return 0;
}
matches = pcre2_get_ovector_pointer(pm);
matches = pcre2_get_ovector_pointer(local_pcre2_match);
#else
ret = pcre_exec(preg->reg, preg->extra, subject, strlen(subject), 0, options, matches, enmatch * 3);
@ -199,9 +200,6 @@ int regex_exec_match(const struct my_regex *preg, const char *subject,
pmatch[i].rm_so = -1;
pmatch[i].rm_eo = -1;
}
#ifdef USE_PCRE2
pcre2_match_data_free(pm);
#endif
return 1;
#else
int match;
@ -228,7 +226,6 @@ int regex_exec_match2(const struct my_regex *preg, char *subject, int length,
int ret;
#ifdef USE_PCRE2
PCRE2_SIZE *matches;
pcre2_match_data *pm;
#else
int matches[MAX_MATCH * 3];
#endif
@ -262,15 +259,11 @@ int regex_exec_match2(const struct my_regex *preg, char *subject, int length,
* space in the matches array.
*/
#ifdef USE_PCRE2
pm = pcre2_match_data_create_from_pattern(preg->reg, NULL);
ret = preg->mfn(preg->reg, (PCRE2_SPTR)subject, (PCRE2_SIZE)length, 0, options, pm, NULL);
if (ret < 0) {
pcre2_match_data_free(pm);
ret = preg->mfn(preg->reg, (PCRE2_SPTR)subject, (PCRE2_SIZE)length, 0, options, local_pcre2_match, NULL);
if (ret < 0)
return 0;
}
matches = pcre2_get_ovector_pointer(pm);
matches = pcre2_get_ovector_pointer(local_pcre2_match);
#else
ret = pcre_exec(preg->reg, preg->extra, subject, length, 0, options, matches, enmatch * 3);
if (ret < 0)
@ -291,9 +284,6 @@ int regex_exec_match2(const struct my_regex *preg, char *subject, int length,
pmatch[i].rm_so = -1;
pmatch[i].rm_eo = -1;
}
#ifdef USE_PCRE2
pcre2_match_data_free(pm);
#endif
return 1;
#else
char old_char = subject[length];
@ -451,6 +441,26 @@ static void regex_register_build_options(void)
INITCALL0(STG_REGISTER, regex_register_build_options);
#ifdef USE_PCRE2
static int init_pcre2_per_thread(void)
{
local_pcre2_match = pcre2_match_data_create(MAX_MATCH - 1, NULL);
if (!local_pcre2_match) {
ha_alert("Failed to allocate PCRE2 match data context for thread %u.\n", tid);
return 0;
}
return 1;
}
static void deinit_pcre2_per_thread(void)
{
pcre2_match_data_free(local_pcre2_match);
}
REGISTER_PER_THREAD_INIT(init_pcre2_per_thread);
REGISTER_PER_THREAD_DEINIT(deinit_pcre2_per_thread);
#endif
/*
* Local variables:
* c-indent-level: 8