linux-kernel - Re: [RFC PATCH] makefile: add debug option to enable function aligned on 32 bytes

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [day] [month] [year] [list]

Message-ID: <20200724010645.GB65362@shbuild999.sh.intel.com>
Date:   Fri, 24 Jul 2020 09:06:45 +0800
From:   Feng Tang <feng.tang@...el.com>
To:     Andrew Morton <akpm@...ux-foundation.org>
Cc:     Masahiro Yamada <masahiroy@...nel.org>,
        Michal Marek <michal.lkml@...kovi.net>,
        linux-kbuild@...r.kernel.org, linux-kernel@...r.kernel.org,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        andi.kleen@...el.com, ying.huang@...el.com,
        andriy.shevchenko@...el.com, philip.li@...el.com,
        rong.a.chen@...el.com
Subject: Re: [RFC PATCH] makefile: add debug option to enable function
 aligned on 32 bytes

On Thu, Jul 23, 2020 at 05:57:04PM -0700, Andrew Morton wrote:
> On Thu, 23 Jul 2020 14:29:33 +0800 Feng Tang <feng.tang@...el.com> wrote:
> 
> > > > gcc has an option '-falign-functions=n' to force text aligned, and with
> > > > that option enabled, some of those performance changes will be gone,
> > > > like [1][2][3].
> > > > 
> > > > Add this option so that developers and 0day can easily find performance
> > > > bump caused by text alignment change,
> > > 
> > > Would they use it this way, or would they simply always enable the
> > > option to reduce the variability?
> > 
> > I may mis-understood it in my last reply. If you are asking about how
> > will developers and 0day use this option, for 0day, I've talked with
> > 0day folks, they may just enable it by default, as 0day cares more about
> > the performance delta caused by a commit (Adding Philip and Rong from
> > 0day).
> 
> OK, thanks, I suspected as much.
> 
> The patch is so simple and probably-will-work, I guess we toss it in
> there and see.

Thanks!

> However it would be good if the 0day people could use it for a while
> and then provide some feedback on whether it is actually proving
> useful.  If not, we get to remove some stuff.

Yes, 0day is a good user to try this.

Thanks,
Feng