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

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Message-ID: <cea4f99c8162405ca4337d20ec0b85d4@AcuMS.aculab.com>
Date:   Tue, 22 Mar 2022 22:27:58 +0000
From:   David Laight <David.Laight@...LAB.COM>
To:     'Jakub Kicinski' <kuba@...nel.org>
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

From: Jakub Kicinski
> Sent: 22 March 2022 18:28
> 
> 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.

Not in the cpu clock count tables I've read.

	David

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