linux-kernel - Re: [lkp-robot] [Kbuild] 050e9baa9d: netperf.Throughput_total

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Date:   Thu, 21 Jun 2018 17:15:09 +0900
From:   Linus Torvalds <torvalds@...ux-foundation.org>
To:     kernel test robot <xiaolong.ye@...el.com>
Cc:     Masahiro Yamada <yamada.masahiro@...ionext.com>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        LKP <lkp@...org>, Huang Ying <ying.huang@...el.com>,
        Aaron Lu <aaron.lu@...el.com>
Subject: Re: [lkp-robot] [Kbuild] 050e9baa9d: netperf.Throughput_total_tps
 -5.6% regression (FYI)

On Thu, Jun 21, 2018 at 5:10 PM kernel test robot <xiaolong.ye@...el.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