From: David Laight <David.Laight@ACULAB.COM>
To: 'Jakub Kicinski' <kuba@kernel.org>
Cc: 'Alexander Lobakin' <alexandr.lobakin@intel.com>,
'Wan Jiabing' <wanjiabing@vivo.com>,
Jesse Brandeburg <jesse.brandeburg@intel.com>,
"Tony Nguyen" <anthony.l.nguyen@intel.com>,
"David S. Miller" <davem@davemloft.net>,
Paolo Abeni <pabeni@redhat.com>,
"intel-wired-lan@lists.osuosl.org"
<intel-wired-lan@lists.osuosl.org>,
"netdev@vger.kernel.org" <netdev@vger.kernel.org>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>
Subject: RE: [PATCH v2] ice: use min_t() to make code cleaner in ice_gnss
Date: Tue, 22 Mar 2022 22:27:58 +0000 [thread overview]
Message-ID: <cea4f99c8162405ca4337d20ec0b85d4@AcuMS.aculab.com> (raw)
In-Reply-To: <20220322112730.482d674d@kicinski-fedora-pc1c0hjn.dhcp.thefacebook.com>
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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next prev parent reply other threads:[~2022-03-22 22:28 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-03-21 13:59 [PATCH v2] ice: use min_t() to make code cleaner in ice_gnss Wan Jiabing
2022-03-21 16:02 ` David Laight
2022-03-22 17:50 ` Alexander Lobakin
2022-03-22 18:12 ` David Laight
2022-03-22 18:27 ` Jakub Kicinski
2022-03-22 21:02 ` Don't do arithmetic on anything smaller than 'int' (was: [PATCH v2] ice: use min_t() to make code cleaner in ice_gnss) Paul Menzel
2022-03-23 12:06 ` [Intel-wired-lan] " Alexander Lobakin
2022-03-22 22:27 ` David Laight [this message]
2022-04-05 4:50 ` [PATCH v2] ice: use min_t() to make code cleaner in ice_gnss G, GurucharanX
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