Received-SPF: pass (google.com: best guess record for domain of linux-kernel-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) client-ip=209.132.180.67;
MIME-Version: 1.0
References: <20190620184523.155756-1-mka@chromium.org> <CAKwvOdn-o9UszRW+MQ9Z0Ds9B2wSVBWUsPBPSF0S2DYxVFYpqA@mail.gmail.com>
In-Reply-To: <CAKwvOdn-o9UszRW+MQ9Z0Ds9B2wSVBWUsPBPSF0S2DYxVFYpqA@mail.gmail.com>
From:   Doug Anderson <dianders@google.com>
Date:   Thu, 20 Jun 2019 13:13:12 -0700
Message-ID: <CAD=FV=WcH=dVeVWznO7Ti5A8HBDRM=rPvvH=-XJ2o1PKXvHAQw@mail.gmail.com>
Subject: Re: [PATCH] gen_compile_command: Add support for separate
 KBUILD_OUTPUT directory
To:     Nick Desaulniers <ndesaulniers@google.com>
Cc:     Matthias Kaehlcke <mka@chromium.org>,
        Tom Roeder <tmroeder@google.com>,
        Masahiro Yamada <yamada.masahiro@socionext.com>,
        LKML <linux-kernel@vger.kernel.org>,
        Raul E Rangel <rrangel@chromium.org>,
        Tom Hughes <tomhughes@chromium.org>,
        Ryan Case <ryandcase@chromium.org>, Yu Liu <yudiliu@google.com>
Content-Type: text/plain; charset="UTF-8"
Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk

Hi,

On Thu, Jun 20, 2019 at 12:53 PM Nick Desaulniers
<ndesaulniers@google.com> wrote:
>
> I do miss Doug's Kbuild caching patches' speedup.

You actually get quite a bit of this by grabbing a new version of
ccache (assuming you use ccache).  :-P  You still have to pay the
penalty (twice) for all the options that are tested that the compiler
_doesn't_ support, but at least you get the cache for the commands
that the compiler does support.

Specifically, make sure you have a ccache with:

    * https://github.com/ccache/ccache/pull/365
    * https://github.com/ccache/ccache/pull/370

I still have it in my thoughts to avoid the penalty for options that
the compiler doesn't support but haven't had time to work on it
recently.


-Doug