linux-kernel - Re: [PATCH 2/4] trace: avoid calling cc-option -mrecord-mcount for every Makefile

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Date:   Mon, 6 Aug 2018 11:07:40 -0700
From:   Andi Kleen <ak@...ux.intel.com>
To:     Vasily Gorbik <gor@...ux.ibm.com>
Cc:     Masahiro Yamada <yamada.masahiro@...ionext.com>,
        Michal Marek <michal.lkml@...kovi.net>,
        Martin Schwidefsky <schwidefsky@...ibm.com>,
        Heiko Carstens <heiko.carstens@...ibm.com>,
        Steven Rostedt <rostedt@...dmis.org>,
        Ingo Molnar <mingo@...hat.com>, linux-kbuild@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-s390@...r.kernel.org
Subject: Re: [PATCH 2/4] trace: avoid calling cc-option -mrecord-mcount for
 every Makefile

On Mon, Aug 06, 2018 at 03:17:44PM +0200, Vasily Gorbik wrote:
> Currently if CONFIG_FTRACE_MCOUNT_RECORD is enabled -mrecord-mcount
> compiler flag support is tested for every Makefile.

Good catch.  Does it make a measurable compile time difference?

> 
> Top 4 cc-option usages:
>     511 -mrecord-mcount
>      11  -fno-stack-protector
>       9 -Wno-override-init
>       2 -fsched-pressure
> 
> To address that move cc-option from scripts/Makefile.build to top Makefile
> and export CC_USING_RECORD_MCOUNT to be used in original place.
> 
> While doing that also add -mrecord-mcount to CC_FLAGS_FTRACE (if gcc
> actually supports it).
> 
> Signed-off-by: Vasily Gorbik <gor@...ux.ibm.com>

Acked-by: Andi Kleen <ak@...ux.intel.com>

-Andi