[PATCH v2 2/7] grep: skip pthreads overhead when using one thread

From: Ævar Arnfjörð Bjarmason <avarab@gmail.com>
Date: May 23, 2017, 19:24 UTC
Message-ID: <20170523192453.14172-3-avarab@gmail.com>
In-Reply-To: <20170523192453.14172-1-avarab@gmail.com>

Skip the administrative overhead of using pthreads when only using one thread. Instead take the non-threaded path which would be taken under NO_PTHREADS.

The threading support was initially added in commit 5b594f457a ("Threaded grep", 2010-01-25) with a hardcoded compile-time number of 8 threads. Later the number of threads was made configurable in commit 89f09dd34e ("grep: add --threads=<num> option and grep.threads configuration", 2015-12-15).

That change did not add any special handling for --threads=1. Now we take a slightly faster path by skipping thread handling entirely when 1 thread is requested.

Signed-off-by: Ævar Arnfjörð Bjarmason <avarab@gmail.com>
---
 builtin/grep.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/builtin/grep.c b/builtin/grep.c
index 12e62fcbf3..bd008cb100 100644
--- a/builtin/grep.c
+++ b/builtin/grep.c
@@ -1238,6 +1238,8 @@ int cmd_grep(int argc, const char **argv, const char *prefix)
 		num_threads = GREP_NUM_THREADS_DEFAULT;
 	else if (num_threads < 0)
 		die(_("invalid number of threads specified (%d)"), num_threads);
+	if (num_threads == 1)
+		num_threads = 0;
 #else
 	if (num_threads)
 		warning(_("no threads support, ignoring --threads"));

-- 
2.13.0.303.g4ebf302169