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Date:   Wed, 29 May 2019 17:02:02 -0600
From:   Jonathan Corbet <corbet@lwn.net>
To:     Mauro Carvalho Chehab <mchehab+samsung@kernel.org>
Cc:     Linux Doc Mailing List <linux-doc@vger.kernel.org>,
        Mauro Carvalho Chehab <mchehab@infradead.org>,
        linux-kernel@vger.kernel.org
Subject: Re: [PATCH 4/5] docs: by default, build docs a lot faster with
 Sphinx >= 1.7
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        <baf19095789f2b2ed0c7a940703037a00cd77850.1558955082.git.mchehab+samsung@kernel.org>
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On Mon, 27 May 2019 08:07:40 -0300
Mauro Carvalho Chehab <mchehab+samsung@kernel.org> wrote:

> Since Sphinx version 1.7, it is possible to use "-jauto" in
> order to speedup documentation builds. On older versions,
> while -j was already supported, one would need to set the
> number of threads manually.
> 
> So, if SPHINXOPTS is not provided, add -jauto, in order to
> speed up the build. That makes it *a lot* times faster than
> without -j.
> 
> If one really wants to slow things down, it can just use:
> 
> 	make SPHINXOPTS=-j1 htmldocs
> 
> Signed-off-by: Mauro Carvalho Chehab <mchehab+samsung@kernel.org>
> ---
>  Documentation/Makefile | 2 ++
>  1 file changed, 2 insertions(+)
> 
> diff --git a/Documentation/Makefile b/Documentation/Makefile
> index 380e24053d6f..794233d05789 100644
> --- a/Documentation/Makefile
> +++ b/Documentation/Makefile
> @@ -28,6 +28,8 @@ ifeq ($(HAVE_SPHINX),0)
>  
>  else # HAVE_SPHINX
>  
> +SPHINXOPTS = $(shell perl -e 'open IN,"sphinx-build --version |"; while (<IN>) { if (m/([\d\.]+)/) { print "-jauto" if ($$1 >= "1.7") } ;} close IN')
> +

So this totally fails to work for me with any version of sphinx, and I'm
not enough of a Perl person to figure it out.  Sometimes I'll see the
sphinx-build output, i.e.:

    sphinx-build 1.8.4

and sometimes (like with 2.0) I don't, but I never get -jauto regardless.
Not sure what's going on here?

Thanks,

jon