[PATCH v4 4/8] grep: add support for the PCRE v1 JIT API
- From
Ævar Arnfjörð Bjarmason <avarab@gmail.com>
- Date
- Jun 1, 2017, 18:20 UTC
- Message-ID
- <20170601182056.31142-5-avarab@gmail.com>
- In-Reply-To
- <20170601182056.31142-1-avarab@gmail.com>
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.
That there's no assignment of `p->pcre1_jit_on = 0` when PCRE_CONFIG_JIT isn't defined isn't a bug. The create_grep_pat() function allocates the grep_pat allocates it with calloc(), so it's guaranteed to be 0 when PCRE_CONFIG_JIT isn't defined.
I you're bisecting and find this change, check that your PCRE isn't older than 8.32. This change intentionally broke really old versions of PCRE, but that's fixed in follow-up commits.
Signed-off-by: Ævar Arnfjörð Bjarmason <avarab@gmail.com> --- grep.c | 40 ++++++++++++++++++++++++++++++++++++---- grep.h | 6 ++++++ 2 files changed, 42 insertions(+), 4 deletions(-)
diff --git a/grep.c b/grep.c index d03d424e5c..ffe95995ee 100644 --- a/grep.c +++ b/grep.c @@ -365,9 +365,22 @@ 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, &p->pcre1_jit_on); + if (p->pcre1_jit_on == 1) { + p->pcre1_jit_stack = pcre_jit_stack_alloc(1, 1024 * 1024); + if (!p->pcre1_jit_stack) + die("Couldn't allocate PCRE JIT stack"); + pcre_assign_jit_stack(p->pcre1_extra_info, NULL, p->pcre1_jit_stack); + } else if (p->pcre1_jit_on != 0) { + die("BUG: The pcre1_jit_on variable should be 0 or 1, not %d", + p->pcre1_jit_on); + } +#endif } static int pcre1match(struct grep_pat *p, const char *line, const char *eol, @@ -378,8 +391,19 @@ static int pcre1match(struct grep_pat *p, const char *line, const char *eol, if (eflags & REG_NOTBOL) flags |= PCRE_NOTBOL; - ret = pcre_exec(p->pcre1_regexp, p->pcre1_extra_info, line, eol - line, - 0, flags, ovector, ARRAY_SIZE(ovector)); +#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 + { + 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 +418,15 @@ 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); - pcre_free(p->pcre1_extra_info); +#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_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