linux-kernel - Re: [ubsan] f0996bc297: netperf.Throughput_total

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Message-ID: <4834add1-711e-b441-1956-1ab2b2d89353@virtuozzo.com>
Date:   Mon, 20 May 2019 12:50:30 +0300
From:   Andrey Ryabinin <aryabinin@...tuozzo.com>
To:     kernel test robot <rong.a.chen@...el.com>
Cc:     Linus Torvalds <torvalds@...ux-foundation.org>,
        LKML <linux-kernel@...r.kernel.org>, lkp@...org
Subject: Re: [ubsan] f0996bc297: netperf.Throughput_total_tps -7.6% regression



On 5/20/19 8:38 AM, kernel test robot wrote:
> Greeting,
> 
> FYI, we noticed a -7.6% regression of netperf.Throughput_total_tps due to commit:
> 
> 
> commit: f0996bc2978e02d2ea898101462b960f6119b18f ("ubsan: Fix nasty -Wbuiltin-declaration-mismatch GCC-9 warnings")
> https://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git master
> 

This can't be right. First of all the commit makes changes only lib/ubsan.c which is compiled only when CONFIG_UBSAN=y.
In your config:
# CONFIG_UBSAN is not set 

But even in the case of enabled UBSAN that commit doesn't change the generated machine code at all.