From 0cc30e0e842a25846e76e09f62a1d425a25ee556 Mon Sep 17 00:00:00 2001 From: Jeff King Date: Thu, 16 Apr 2015 05:01:38 -0400 Subject: strbuf_getwholeline: use getdelim if it is available We spend a lot of time in strbuf_getwholeline in a tight loop reading characters from a stdio handle into a buffer. The libc getdelim() function can do this for us with less overhead. It's in POSIX.1-2008, and was a GNU extension before that. Therefore we can't rely on it, but can fall back to the existing getc loop when it is not available. The HAVE_GETDELIM knob is turned on automatically for Linux, where we have glibc. We don't need to set any new feature-test macros, because we already define _GNU_SOURCE. Other systems that implement getdelim may need to other macros (probably _POSIX_C_SOURCE >= 200809L), but we can address that along with setting the Makefile knob after testing the feature on those systems. Running "git rev-parse refs/heads/does-not-exist" on a repo with an extremely large (1.6GB) packed-refs file went from (best-of-5): real 0m8.601s user 0m8.084s sys 0m0.524s to: real 0m6.768s user 0m6.340s sys 0m0.432s for a wall-clock speedup of 21%. Based on a patch from Rasmus Villemoes . Signed-off-by: Jeff King Signed-off-by: Junio C Hamano --- config.mak.uname | 1 + 1 file changed, 1 insertion(+) (limited to 'config.mak.uname') diff --git a/config.mak.uname b/config.mak.uname index f4e77cb9e5..d26665fa54 100644 --- a/config.mak.uname +++ b/config.mak.uname @@ -36,6 +36,7 @@ ifeq ($(uname_S),Linux) HAVE_DEV_TTY = YesPlease HAVE_CLOCK_GETTIME = YesPlease HAVE_CLOCK_MONOTONIC = YesPlease + HAVE_GETDELIM = YesPlease endif ifeq ($(uname_S),GNU/kFreeBSD) HAVE_ALLOCA_H = YesPlease -- cgit v1.2.1