Change the grep PCRE v1 code to use JIT when available. When PCRE
support was initially added in commit 63e7e9d8b6 ("git-grep: Learn
PCRE", 2011-05-09) PCRE had no JIT support, it was integrated into
8.20 released on 2011-10-21.
Enabling JIT support usually improves performance by more than
40%. The pattern compilation times are relatively slower, but those
relative numbers are tiny, and are easily made back in all but the
most trivial cases of grep. Detailed benchmarks & overview of
compilation times is at: http://sljit.sourceforge.net/pcre.html
With this change the difference in a t/perf/p7820-grep-engines.sh run
is, with just the /perl/ tests shown:
$ GIT_PERF_REPEAT_COUNT=30 GIT_PERF_LARGE_REPO=~/g/linux GIT_PERF_MAKE_OPTS='-j8 USE_LIBPCRE=YesPlease CC=~/perl5/installed/bin/gcc NO_R_TO_GCC_LINKER=YesPlease CFLAGS=-O3 LIBPCREDIR=/home/avar/g/pcre/inst LDFLAGS=-Wl,-rpath,/home/avar/g/pcre/inst/lib' ./run HEAD~ HEAD p7820-grep-engines.sh
Test HEAD~ HEAD
---------------------------------------------------------------------------------------
7820.3: perl grep 'how.to' 0.35(1.11+0.43) 0.23(0.42+0.46) -34.3%
7820.7: perl grep '^how to' 0.64(2.71+0.36) 0.27(0.66+0.44) -57.8%
7820.11: perl grep '[how] to' 0.63(2.51+0.42) 0.33(0.98+0.39) -47.6%
7820.15: perl grep '(e.t[^ ]*|v.ry) rare' 1.17(5.61+0.35) 0.34(1.08+0.46) -70.9%
7820.19: perl grep 'm(ú|u)lt.b(æ|y)te' 0.43(1.52+0.44) 0.30(0.88+0.42) -30.2%
The conditional support for JIT is implemented as suggested in the
pcrejit(3) man page. E.g. defining PCRE_STUDY_JIT_COMPILE to 0 if it's
not present.
The implementation is relatively verbose because even if
PCRE_CONFIG_JIT is defined only a call to pcre_config() can determine
if the JIT is available, and if so the faster pcre_jit_exec() function
should be called instead of pcre_exec(), and a different (but not
complimentary!) function needs to be called to free pcre1_extra_info.
There's no graceful fallback if pcre_jit_stack_alloc() fails under
PCRE_CONFIG_JIT, instead the program will simply abort. I don't think
this is worth handling gracefully, it'll only fail in cases where
malloc() doesn't work, in which case we're screwed anyway.
Signed-off-by: Ævar Arnfjörð Bjarmason <avarab@xxxxxxxxx>
---
grep.c | 34 +++++++++++++++++++++++++++++++++-
grep.h | 6 ++++++
2 files changed, 39 insertions(+), 1 deletion(-)
diff --git a/grep.c b/grep.c
index 1157529115..49e9aed457 100644
--- a/grep.c
+++ b/grep.c
@@ -351,6 +351,9 @@ static void compile_pcre1_regexp(struct grep_pat *p, const struct grep_opt *opt)
const char *error;
int erroffset;
int options = PCRE_MULTILINE;
+#ifdef PCRE_CONFIG_JIT
+ int canjit;
+#endif
if (opt->ignore_case) {
if (has_non_ascii(p->pattern))
@@ -365,9 +368,20 @@ static void compile_pcre1_regexp(struct grep_pat *p, const struct grep_opt *opt)
if (!p->pcre1_regexp)
compile_regexp_failed(p, error);
- p->pcre1_extra_info = pcre_study(p->pcre1_regexp, 0, &error);
+ p->pcre1_extra_info = pcre_study(p->pcre1_regexp, PCRE_STUDY_JIT_COMPILE, &error);
if (!p->pcre1_extra_info && error)
die("%s", error);
+
+#ifdef PCRE_CONFIG_JIT
+ pcre_config(PCRE_CONFIG_JIT, &canjit);
+ if (canjit == 1) {
+ p->pcre1_jit_stack = pcre_jit_stack_alloc(1, 1024 * 1024);
+ if (!p->pcre1_jit_stack)
+ die("BUG: Couldn't allocate PCRE JIT stack");
+ pcre_assign_jit_stack(p->pcre1_extra_info, NULL, p->pcre1_jit_stack);
+ p->pcre1_jit_on = 1;
+ }
+#endif
}
static int pcre1match(struct grep_pat *p, const char *line, const char *eol,
@@ -378,8 +392,17 @@ static int pcre1match(struct grep_pat *p, const char *line, const char *eol,
if (eflags & REG_NOTBOL)
flags |= PCRE_NOTBOL;
+#ifdef PCRE_CONFIG_JIT
+ if (p->pcre1_jit_on)
+ ret = pcre_jit_exec(p->pcre1_regexp, p->pcre1_extra_info, line,
+ eol - line, 0, flags, ovector,
+ ARRAY_SIZE(ovector), p->pcre1_jit_stack);
+ else
+#endif
+ /* PCRE_CONFIG_JIT !p->pcre1_jit_on else branch */
ret = pcre_exec(p->pcre1_regexp, p->pcre1_extra_info, line, eol - line,
0, flags, ovector, ARRAY_SIZE(ovector));
+
if (ret < 0 && ret != PCRE_ERROR_NOMATCH)
die("pcre_exec failed with error code %d", ret);
if (ret > 0) {
@@ -394,7 +417,16 @@ static int pcre1match(struct grep_pat *p, const char *line, const char *eol,
static void free_pcre1_regexp(struct grep_pat *p)
{
pcre_free(p->pcre1_regexp);
+
+#ifdef PCRE_CONFIG_JIT
+ if (p->pcre1_jit_on) {
+ pcre_free_study(p->pcre1_extra_info);
+ pcre_jit_stack_free(p->pcre1_jit_stack);
+ } else
+#endif
+ /* PCRE_CONFIG_JIT !p->pcre1_jit_on else branch */
pcre_free(p->pcre1_extra_info);
+
pcre_free((void *)p->pcre1_tables);
}
#else /* !USE_LIBPCRE1 */
diff --git a/grep.h b/grep.h
index 38ac82b638..14f47189f9 100644
--- a/grep.h
+++ b/grep.h
@@ -3,9 +3,13 @@
#include "color.h"
#ifdef USE_LIBPCRE1
#include <pcre.h>
+#ifndef PCRE_STUDY_JIT_COMPILE
+#define PCRE_STUDY_JIT_COMPILE 0
+#endif
#else
typedef int pcre;
typedef int pcre_extra;
+typedef int pcre_jit_stack;
#endif
#include "kwset.h"
#include "thread-utils.h"
@@ -48,7 +52,9 @@ struct grep_pat {
regex_t regexp;
pcre *pcre1_regexp;
pcre_extra *pcre1_extra_info;
+ pcre_jit_stack *pcre1_jit_stack;
const unsigned char *pcre1_tables;
+ int pcre1_jit_on;
kwset_t kws;
unsigned fixed:1;
unsigned ignore_case:1;
--
2.13.0.303.g4ebf302169