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[PATCH v3] Add git-grep threads param

From
Victor Leschuk <vleschuk@gmail.com>
Date
Oct 26, 2015, 12:32 UTC
Message-ID
<1445862733-838-1-git-send-email-vleschuk@accesssoftek.com>

Make number of git-grep worker threads a configuration parameter. According to several tests on systems with different number of CPU cores the hard-coded number of 8 threads is not optimal for all systems: tuning this parameter can significantly speed up grep performance.

Signed-off-by: Victor Leschuk <vleschuk@accesssoftek.com>
---
 Documentation/config.txt               |  4 ++++
 Documentation/git-grep.txt             |  4 ++++
 builtin/grep.c                         | 34 ++++++++++++++++++++++++++--------
 contrib/completion/git-completion.bash |  1 +
 grep.c                                 | 10 ++++++++++
 grep.h                                 |  2 ++
 6 files changed, 47 insertions(+), 8 deletions(-)
diff --git a/Documentation/config.txt b/Documentation/config.txt
index 391a0c3..1c95587 100644
--- a/Documentation/config.txt
+++ b/Documentation/config.txt
@@ -1447,6 +1447,10 @@ grep.extendedRegexp::
 	option is ignored when the 'grep.patternType' option is set to a value
 	other than 'default'.
 
+grep.threads::
+	Number of grep worker threads, use it to tune up performance on
+	multicore machines. Default value is 8.
+
 gpg.program::
 	Use this custom program instead of "gpg" found on $PATH when
 	making or verifying a PGP signature. The program must support the
diff --git a/Documentation/git-grep.txt b/Documentation/git-grep.txt
index 4a44d6d..fbd4f83 100644
--- a/Documentation/git-grep.txt
+++ b/Documentation/git-grep.txt
@@ -22,6 +22,7 @@ SYNOPSIS
 	   [--color[=<when>] | --no-color]
 	   [--break] [--heading] [-p | --show-function]
 	   [-A <post-context>] [-B <pre-context>] [-C <context>]
+	   [--threads <num>]
 	   [-W | --function-context]
 	   [-f <file>] [-e] <pattern>
 	   [--and|--or|--not|(|)|-e <pattern>...]
@@ -220,6 +221,9 @@ OPTIONS
 	Show <num> leading lines, and place a line containing
 	`--` between contiguous groups of matches.
 
+--threads <num>::
+	Set number of worker threads to <num>. Default is 8.
+
 -W::
 --function-context::
 	Show the surrounding text from the previous line containing a
diff --git a/builtin/grep.c b/builtin/grep.c
index d04f440..5ef1b07 100644
--- a/builtin/grep.c
+++ b/builtin/grep.c
@@ -27,8 +27,7 @@ static char const * const grep_usage[] = {
 static int use_threads = 1;
 
 #ifndef NO_PTHREADS
-#define THREADS 8
-static pthread_t threads[THREADS];
+static pthread_t *threads;
 
 /* We use one producer thread and THREADS consumer
  * threads. The producer adds struct work_items to 'todo' and the
@@ -206,7 +205,8 @@ static void start_threads(struct grep_opt *opt)
 		strbuf_init(&todo[i].out, 0);
 	}
 
-	for (i = 0; i < ARRAY_SIZE(threads); i++) {
+	threads = xcalloc(opt->num_threads, sizeof(pthread_t));
+	for (i = 0; i < opt->num_threads; i++) {
 		int err;
 		struct grep_opt *o = grep_opt_dup(opt);
 		o->output = strbuf_out;
@@ -220,7 +220,7 @@ static void start_threads(struct grep_opt *opt)
 	}
 }
 
-static int wait_all(void)
+static int wait_all(struct grep_opt *opt)
 {
 	int hit = 0;
 	int i;
@@ -238,12 +238,14 @@ static int wait_all(void)
 	pthread_cond_broadcast(&cond_add);
 	grep_unlock();
 
-	for (i = 0; i < ARRAY_SIZE(threads); i++) {
+	for (i = 0; i < opt->num_threads; i++) {
 		void *h;
 		pthread_join(threads[i], &h);
 		hit |= (int) (intptr_t) h;
 	}
 
+	free(threads);
+
 	pthread_mutex_destroy(&grep_mutex);
 	pthread_mutex_destroy(&grep_read_mutex);
 	pthread_mutex_destroy(&grep_attr_mutex);
@@ -256,7 +258,7 @@ static int wait_all(void)
 }
 #else /* !NO_PTHREADS */
 
-static int wait_all(void)
+static int wait_all(struct grep_opt *opt)
 {
 	return 0;
 }
@@ -702,6 +704,8 @@ int cmd_grep(int argc, const char **argv, const char *prefix)
 			N_("show <n> context lines before matches")),
 		OPT_INTEGER('A', "after-context", &opt.post_context,
 			N_("show <n> context lines after matches")),
+		OPT_INTEGER(0, "threads", &opt.num_threads,
+			N_("use <n> worker threads")),
 		OPT_NUMBER_CALLBACK(&opt, N_("shortcut for -C NUM"),
 			context_callback),
 		OPT_BOOL('p', "show-function", &opt.funcname,
@@ -832,8 +836,22 @@ int cmd_grep(int argc, const char **argv, const char *prefix)
 	}
 
 #ifndef NO_PTHREADS
-	if (list.nr || cached || online_cpus() == 1)
+	if (!opt.num_threads) {
+		use_threads = 0; /* User explicitely told not to use threads */
+	}
+	else if (list.nr || cached) {
+		use_threads = 0; /* Can not multi-thread object lookup */
+	}
+	else if (opt.num_threads >= 0) {
+		use_threads = 1; /* User explicitely set the number of threads */
+	}
+	else if (online_cpus() <= 1) {
 		use_threads = 0;
+	}
+	else {
+		use_threads = 1;
+		opt.num_threads = GREP_NUM_THREADS_DEFAULT;
+	}
 #else
 	use_threads = 0;
 #endif
@@ -910,7 +928,7 @@ int cmd_grep(int argc, const char **argv, const char *prefix)
 	}
 
 	if (use_threads)
-		hit |= wait_all();
+		hit |= wait_all(&opt);
 	if (hit && show_in_pager)
 		run_pager(&opt, prefix);
 	free_grep_patterns(&opt);
diff --git a/contrib/completion/git-completion.bash b/contrib/completion/git-completion.bash
index 482ca84..390d9c0 100644
--- a/contrib/completion/git-completion.bash
+++ b/contrib/completion/git-completion.bash
@@ -1310,6 +1310,7 @@ _git_grep ()
 			--full-name --line-number
 			--extended-regexp --basic-regexp --fixed-strings
 			--perl-regexp
+			--threads
 			--files-with-matches --name-only
 			--files-without-match
 			--max-depth
diff --git a/grep.c b/grep.c
index 7b2b96a..b53fb14 100644
--- a/grep.c
+++ b/grep.c
@@ -40,6 +40,7 @@ void init_grep_defaults(void)
 	color_set(opt->color_selected, "");
 	color_set(opt->color_sep, GIT_COLOR_CYAN);
 	opt->color = -1;
+	opt->num_threads = -1;
 }
 
 static int parse_pattern_type_arg(const char *opt, const char *arg)
@@ -124,6 +125,14 @@ int grep_config(const char *var, const char *value, void *cb)
 			return config_error_nonbool(var);
 		return color_parse(value, color);
 	}
+
+	if (!strcmp(var, "grep.threads")) {
+		int threads = git_config_int(var, value);
+		if (threads < 0)
+			die("invalid number of threads specified (%d)", threads);
+		opt->num_threads = threads;
+		return 0;
+	}
 	return 0;
 }
 
@@ -150,6 +159,7 @@ void grep_init(struct grep_opt *opt, const char *prefix)
 	opt->pathname = def->pathname;
 	opt->regflags = def->regflags;
 	opt->relative = def->relative;
+	opt->num_threads = def->num_threads;
 
 	color_set(opt->color_context, def->color_context);
 	color_set(opt->color_filename, def->color_filename);
diff --git a/grep.h b/grep.h
index 95f197a..bb20456 100644
--- a/grep.h
+++ b/grep.h
@@ -132,6 +132,8 @@ struct grep_opt {
 	unsigned pre_context;
 	unsigned post_context;
 	unsigned last_shown;
+#define GREP_NUM_THREADS_DEFAULT 8
+	int num_threads;
 	int show_hunk_mark;
 	int file_break;
 	int heading;

-- 
2.6.2.281.g222e106.dirty
Next: John Keeping
Message 1 of 7 in “Add git-grep threads param”
  1. Add git-grep threads paramVictor Leschuk, Oct 26, 2015
  2. John KeepingOct 26, 2015
  3. Victor LeschukOct 27, 2015
  4. John KeepingOct 27, 2015
  5. Victor LeschukOct 27, 2015
  6. John KeepingOct 27, 2015
  7. Victor LeschukOct 27, 2015

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