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: <20180621080624.GO11011@yexl-desktop>
In-Reply-To: <20180621080624.GO11011@yexl-desktop>
From:   Linus Torvalds <torvalds@linux-foundation.org>
Date:   Thu, 21 Jun 2018 17:15:09 +0900
Message-ID: <CA+55aFxXCD8qLfHcnshLR2_Feb=RLkOFfCeqPF_sShy7rK2cAw@mail.gmail.com>
Subject: Re: [lkp-robot] [Kbuild] 050e9baa9d: netperf.Throughput_total_tps
 -5.6% regression (FYI)
To:     kernel test robot <xiaolong.ye@intel.com>
Cc:     Masahiro Yamada <yamada.masahiro@socionext.com>,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
        LKP <lkp@01.org>, Huang Ying <ying.huang@intel.com>,
        Aaron Lu <aaron.lu@intel.com>
Content-Type: text/plain; charset="UTF-8"
Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk

On Thu, Jun 21, 2018 at 5:10 PM kernel test robot <xiaolong.ye@intel.com> wrote:
>
> FYI, we noticed a -5.6% regression of netperf.Throughput_total_tps due to commit 050e9b ("Kbuild: rename CC_STACKPROTECTOR[_STRONG] config variables")

That's perhaps a surprisingly large cost to stack protector, but you
did move from "no stack protector at all":

> $ grep STACKPROTECTOR config-4.17.0-11782-gbe779f0
> CONFIG_HAVE_CC_STACKPROTECTOR=y
> CONFIG_CC_HAS_STACKPROTECTOR_NONE=y
> # CONFIG_CC_STACKPROTECTOR is not set
> CONFIG_CC_HAS_SANE_STACKPROTECTOR=y

To having the *strong* stack protector enabled:

> $ grep STACKPROTECTOR config-4.17.0-11783-g050e9baa
> CONFIG_HAVE_CC_STACKPROTECTOR=y
> CONFIG_CC_HAS_STACKPROTECTOR_NONE=y
> CONFIG_STACKPROTECTOR=y
> CONFIG_STACKPROTECTOR_STRONG=y
> CONFIG_CC_HAS_SANE_STACKPROTECTOR=y

so you're testing the "no overhead" case to the "worst overhead" case.

                Linus