linux-kernel - Re: [PATCH v2] ice: use min_t() to make code cleaner in ice

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

Message-ID: <20220322112730.482d674d@kicinski-fedora-pc1c0hjn.dhcp.thefacebook.com>
Date:   Tue, 22 Mar 2022 11:27:30 -0700
From:   Jakub Kicinski <kuba@...nel.org>
To:     David Laight <David.Laight@...LAB.COM>
Cc:     'Alexander Lobakin' <alexandr.lobakin@...el.com>,
        'Wan Jiabing' <wanjiabing@...o.com>,
        Jesse Brandeburg <jesse.brandeburg@...el.com>,
        Tony Nguyen <anthony.l.nguyen@...el.com>,
        "David S. Miller" <davem@...emloft.net>,
        Paolo Abeni <pabeni@...hat.com>,
        "intel-wired-lan@...ts.osuosl.org" <intel-wired-lan@...ts.osuosl.org>,
        "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v2] ice: use min_t() to make code cleaner in ice_gnss

On Tue, 22 Mar 2022 18:12:08 +0000 David Laight wrote:
> > > Oh FFS why is that u16?
> > > Don't do arithmetic on anything smaller than 'int'  
> > 
> > Any reasoning? I don't say it's good or bad, just want to hear your
> > arguments (disasms, perf and object code measurements) etc.  
> 
> Look at the object code on anything except x86.
> The compiler has to add instruction to mask the value
> (which is in a full sized register) down to 16 bits
> after every arithmetic operation.

Isn't it also slower on some modern x86 CPUs?
I could have sworn someone mentioned that in the past.