Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx> writes:
> Yes. Also, I'm not sure if the 15% possible improvement on my SSD case
> is even worth it for something that in the end isn't necessarily the
> common case.
Cold cache being uncommon case would be forever true but more and
more people are on SSD, and 15% is not a trivial improvement.
> Are there people out there who use "git grep" over NFS and have been
> unhappy with performance? If are willing to recompile git with a
> different THREAD value in builtin/grep.c,...
OK, you have to recompile at least once for experiment, so perhaps
building the test binary with this patch may help.
builtin/grep.c | 30 ++++++++++++++++++++++--------
1 file changed, 22 insertions(+), 8 deletions(-)
diff --git a/builtin/grep.c b/builtin/grep.c
index 159e65d..f635cd5 100644
--- a/builtin/grep.c
+++ b/builtin/grep.c
@@ -26,12 +26,14 @@ static char const * const grep_usage[] = {
static int use_threads = 1;
#ifndef NO_PTHREADS
-#define THREADS 8
-static pthread_t threads[THREADS];
+#define MAX_THREADS 100
+static int num_threads = 8;
+static pthread_t threads[MAX_THREADS];
-/* We use one producer thread and THREADS consumer
- * threads. The producer adds struct work_items to 'todo' and the
- * consumers pick work items from the same array.
+/*
+ * We use one producer thread and THREADS consumer threads. The
+ * producer adds struct work_items to 'todo' and the consumers pick
+ * work items from the same array.
*/
struct work_item {
struct grep_source source;
@@ -205,7 +207,7 @@ static void start_threads(struct grep_opt *opt)
strbuf_init(&todo[i].out, 0);
}
- for (i = 0; i < ARRAY_SIZE(threads); i++) {
+ for (i = 0; i < num_threads; i++) {
int err;
struct grep_opt *o = grep_opt_dup(opt);
o->output = strbuf_out;
@@ -237,7 +239,7 @@ static int wait_all(void)
pthread_cond_broadcast(&cond_add);
grep_unlock();
- for (i = 0; i < ARRAY_SIZE(threads); i++) {
+ for (i = 0; i < num_threads; i++) {
void *h;
pthread_join(threads[i], &h);
hit |= (int) (intptr_t) h;
@@ -636,6 +638,7 @@ int cmd_grep(int argc, const char **argv, const char *prefix)
int i;
int dummy;
int use_index = 1;
+ int num_threads_explicit = -1;
int pattern_type_arg = GREP_PATTERN_TYPE_UNSPECIFIED;
struct option options[] = {
@@ -743,6 +746,8 @@ int cmd_grep(int argc, const char **argv, const char *prefix)
N_("allow calling of grep(1) (ignored by this build)")),
{ OPTION_CALLBACK, 0, "help-all", &options, NULL, N_("show usage"),
PARSE_OPT_HIDDEN | PARSE_OPT_NOARG, help_callback },
+ OPT_INTEGER(0, "threads", &num_threads_explicit,
+ N_("use threads when searching")),
OPT_END()
};
@@ -773,6 +778,15 @@ int cmd_grep(int argc, const char **argv, const char *prefix)
PARSE_OPT_NO_INTERNAL_HELP);
grep_commit_pattern_type(pattern_type_arg, &opt);
+ if (MAX_THREADS <= num_threads_explicit) {
+ warning("limiting --threads to %d", MAX_THREADS);
+ num_threads = MAX_THREADS;
+ } else if (num_threads_explicit < 0) {
+ ; /* keep num_threads to compiled-in default */
+ } else {
+ num_threads = num_threads_explicit;
+ }
+
if (use_index && !startup_info->have_repository)
/* die the same way as if we did it at the beginning */
setup_git_directory();
@@ -834,7 +848,7 @@ int cmd_grep(int argc, const char **argv, const char *prefix)
}
#ifndef NO_PTHREADS
- if (list.nr || cached || online_cpus() == 1)
+ if ((list.nr || cached || online_cpus() == 1) && num_threads_explicit < 0)
use_threads = 0;
#else
use_threads = 0;
--
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