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Wed, 1 Aug 2018 18:03:04 +0000 From: Yongseok Koh To: Stephen Hemminger CC: Adrien Mazarguil , "dev@dpdk.org" Thread-Topic: [dpdk-dev] [PATCH 0/5] remove usage of register keyword in C Thread-Index: AQHUKOvm8fvVdThTyUaSyf8D4BmtkaSpitIAgAAWD4CAAZENAA== Date: Wed, 1 Aug 2018 18:03:04 +0000 Message-ID: <50204CDA-B4AD-44C8-AB07-2FE9C2A412C0@mellanox.com> References: <20180731163059.27085-1-stephen@networkplumber.org> <20180731164840.GD5211@6wind.com> <20180731110737.38555f02@xeon-e3> In-Reply-To: <20180731110737.38555f02@xeon-e3> Accept-Language: en-US Content-Language: en-US X-MS-Has-Attach: X-MS-TNEF-Correlator: authentication-results: spf=none (sender IP is ) smtp.mailfrom=yskoh@mellanox.com; x-originating-ip: [209.116.155.178] x-ms-publictraffictype: Email x-microsoft-exchange-diagnostics: 1; HE1PR0501MB2252; 6:R4WIjsR6PDfDGCnjWSUqFGMzqv7n4pq3m5oFKvv73kWqgZMjH9by27L3AVgga+RFIbnBiYcs/pzdsV0uFw26vHozZAtsIDmqgMV+jIQP13fmHTu8d9oSX4iEUP/7Sx7fekTIWz4ruvRs4pQTHZBQ57Ar79gLGcQKGu4Yfu//loN/8yli3PwdN58EJfQC+Mb6LpIIVwJcyhgxfv5jjXDXyNjibV20AyGTbKOtoYTdDLTQM/yI1FZh+VxOXN+ul8g6dLoMntB2OMGwxhJ/+4t1miUhOuIfGCgNj1ggY7fYpdFidRYWkH9yXukb5Svy/T/JpfxSmNscVERG/uQkI1fp2cKuZShKYCHYhrP+CnEZ6DkXF/lJAcy3xLzb1RsIUTEO0p9WE6qrDAMFVAnia6S3bVPvVXaVJtcbBNusuxaA8Pb90+XOi8ypq3dnQlodDzWancsO3EzwLdK1R2BVJQZ1AA==; 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DIR:OUT; SFP:1101; SCL:1; SRVR:HE1PR0501MB2252; H:HE1PR0501MB2043.eurprd05.prod.outlook.com; FPR:; SPF:None; LANG:en; PTR:InfoNoRecords; MX:1; A:1; received-spf: None (protection.outlook.com: mellanox.com does not designate permitted sender hosts) x-microsoft-antispam-message-info: YQ3AR+6c0xYhLAMzuU/NHMgY53lZOzlAve3KpeRHE+8KYF5i4CfP4r4C2ok2Sp9zJJ7eNd2qsLCyL7Yt7GGmg9pwxLQkrx0MxM1+ho+JEZYz5W6qN4GRbj9jVlakHT8NczuqULQ5j8NbByswn1WyirX9Bjy5/i9IzDGLY11vfAw+bPH+8Im63R38ZZ4kgxHzFakUvIm/0cC4fERmAvEYdrXJ+dY6Nt68TQ770ylwSXFUGAFT+LsTM69Obn1sq/1ZVDfXPY9IioW16EmiGCRVyt874Hgw/+NJEYymQP7Vi4TQWBD8U5HpDSXFXx6Q+qx0llvSHRlizaA2s0VbVfNFDPElcW1Nu3VTbZxCpGwhNrI= spamdiagnosticoutput: 1:99 spamdiagnosticmetadata: NSPM Content-Type: text/plain; charset="us-ascii" Content-ID: <785EDC668DA45540ADD4AC321F73F944@eurprd05.prod.outlook.com> Content-Transfer-Encoding: quoted-printable MIME-Version: 1.0 X-OriginatorOrg: Mellanox.com X-MS-Exchange-CrossTenant-Network-Message-Id: 477acb64-3285-40f6-08af-08d5f7d90737 X-MS-Exchange-CrossTenant-originalarrivaltime: 01 Aug 2018 18:03:04.3053 (UTC) X-MS-Exchange-CrossTenant-fromentityheader: Hosted X-MS-Exchange-CrossTenant-id: a652971c-7d2e-4d9b-a6a4-d149256f461b X-MS-Exchange-Transport-CrossTenantHeadersStamped: HE1PR0501MB2252 Subject: Re: [dpdk-dev] [PATCH 0/5] remove usage of register keyword in C X-BeenThere: dev@dpdk.org X-Mailman-Version: 2.1.15 Precedence: list List-Id: DPDK patches and discussions List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Wed, 01 Aug 2018 18:03:06 -0000 > On Jul 31, 2018, at 11:07 AM, Stephen Hemminger wrote: >=20 > On Tue, 31 Jul 2018 18:48:40 +0200 > Adrien Mazarguil wrote: >=20 >> On Tue, Jul 31, 2018 at 09:30:54AM -0700, Stephen Hemminger wrote: >>> Declaring variables as register in C is a leftover from an earlier >>> era (like cassette tape decks in cars). =20 >>=20 >> I don't agree here. It's a hint for compilers and developers that the >> address of such variables won't be needed (and cannot be taken) to enabl= e >> whatever optimizations are possible knowing this. >>=20 >> Somewhat like inline functions, it's not a forced optimization, just a >> useful hint that shouldn't hurt if used wisely. >>=20 >> Besides, cassette decks are not dead yet :) >=20 > If you look at the code, that is not how register is being used (ie. don'= t take > address of this). It seems like an attempt at optimization. I know compilers are smart enough and the occurrences in mlx4/5 were made f= rom my old fashioned habit. But, I don't see any urgency to push this patch in = RC stage even though I'm 99% sure that it is harmless. And in general I don't = even understand why we can't live with that if it isn't harmful (or a violation)= but informative. I mean no badness but at least one goodness :-) Thanks, Yongseok