From mboxrd@z Thu Jan  1 00:00:00 1970
From: Jeff King <peff@peff.net>
Subject: Re: [PATCH v2 3/3] grep: disable threading in all but worktree case
Date: Tue, 6 Dec 2011 23:24:31 -0500
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Cc: git@vger.kernel.org, Eric Herman <eric@freesa.org>,
	Junio C Hamano <gitster@pobox.com>
To: =?utf-8?B?UmVuw6k=?= Scharfe <rene.scharfe@lsrfire.ath.cx>
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On Tue, Dec 06, 2011 at 11:48:26PM +0100, Ren=C3=A9 Scharfe wrote:

>  #ifndef NO_PTHREADS
> -	if (use_threads) {
> +	if (nr_threads > 0) {
>  		grep_sha1_async(opt, name, sha1);
>  		return 0;
>  	} else

Should this be "if (nr_threads > 1)"?

As a user, I would do:

  git grep --threads=3D1 ...

if I wanted a single-threaded process. Instead, we actually spawn a
sub-thread and do all of the locking, which has a measurable cost:

  $ time git grep --threads=3D0 SIMPLE HEAD >/dev/null
  real    0m2.994s
  user    0m2.932s
  sys     0m0.060s

  $ time git grep --threads=3D1 SIMPLE HEAD >/dev/null
  real    0m3.407s
  user    0m3.392s
  sys     0m0.140s

Should --threads=3D1 be equivalent to --threads=3D0?

-Peff