Re: [PATCH v2 2/7] grep: skip pthreads overhead when using one thread
From: Junio C Hamano <hidden>
Date: 2017-05-24 04:45:49
Ævar Arnfjörð Bjarmason [off-list ref] writes:
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.OK, this is what Peff and you were discussing in the earlier round, having the controller do the work himself, instead of sitting and waiting for a sole worker to finish the work. Looks good. Thanks.
quoted hunk
Signed-off-by: Ævar Arnfjörð Bjarmason <redacted> --- 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"));