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Wed, 28 Nov 2018 05:31:57 +0000 From: Honnappa Nagarahalli <Honnappa.Nagarahalli@arm.com> To: "Van Haaren, Harry" <harry.van.haaren@intel.com>, Stephen Hemminger <stephen@networkplumber.org> CC: "dev@dpdk.org" <dev@dpdk.org>, nd <nd@arm.com>, Dharmik Thakkar <Dharmik.Thakkar@arm.com>, Malvika Gupta <Malvika.Gupta@arm.com>, "Gavin Hu (Arm Technology China)" <Gavin.Hu@arm.com>, Honnappa Nagarahalli <Honnappa.Nagarahalli@arm.com>, nd <nd@arm.com> Thread-Topic: [dpdk-dev] [RFC 0/3] tqs: add thread quiescent state library Thread-Index: AQHUhqB8tEevwcHR9UqXBYKYUzkOUKVkOZ6AgABmmXA= Date: Wed, 28 Nov 2018 05:31:56 +0000 Message-ID: <AM6PR08MB3672F16A8B729EF14E38A2D098D10@AM6PR08MB3672.eurprd08.prod.outlook.com> References: <20181122033055.3431-1-honnappa.nagarahalli@arm.com> <20181127142803.423c9b00@xeon-e3> <E923DB57A917B54B9182A2E928D00FA65E31B1F7@IRSMSX102.ger.corp.intel.com> In-Reply-To: <E923DB57A917B54B9182A2E928D00FA65E31B1F7@IRSMSX102.ger.corp.intel.com> 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=Honnappa.Nagarahalli@arm.com; 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DIR:OUT; SFP:1101; SCL:1; SRVR:AM6PR08MB4119; H:AM6PR08MB3672.eurprd08.prod.outlook.com; FPR:; SPF:None; LANG:en; PTR:InfoNoRecords; MX:1; A:1; received-spf: None (protection.outlook.com: arm.com does not designate permitted sender hosts) x-microsoft-antispam-message-info: hETRXuCXXhjt7MQbrnQcGXkLGvnD6OB3zb8JHSydzz5/M9ZyoEcwhcfXH782+8d+j8iB+7ofgDcNuklk7Wf/ZCy6Xpi65rGLUf6zln4Teh+9m+8kV1dqVV2Qb/Fo7ui+Z/mprzH/YJTDJ/kA/3IfZLbCQgVTP4JS5QMFGLn+goL1b1cEsrPX3FYzUVwhYDxwT+s2mS37IXKeB5z69dopEqpA59KqMZSSRBO3sp+kmaWpsRH6hcI/1UG1SYQDCIZih6UKcfklVbZk3hJCkhPGr1Wz94ANeDpe/Z4HH4g+/6emDTeF5JqyJA88F6DexWIIq9Y9eB8L+jelELl8w2SQrCi7XSWK78G7boAcFedIoiE= spamdiagnosticoutput: 1:99 spamdiagnosticmetadata: NSPM Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: quoted-printable MIME-Version: 1.0 X-OriginatorOrg: arm.com X-MS-Exchange-CrossTenant-Network-Message-Id: 322bd4ba-e4c0-40f1-6df6-08d654f2d024 X-MS-Exchange-CrossTenant-originalarrivaltime: 28 Nov 2018 05:31:56.9746 (UTC) X-MS-Exchange-CrossTenant-fromentityheader: Hosted X-MS-Exchange-CrossTenant-id: f34e5979-57d9-4aaa-ad4d-b122a662184d X-MS-Exchange-Transport-CrossTenantHeadersStamped: AM6PR08MB4119 Subject: Re: [dpdk-dev] [RFC 0/3] tqs: add thread quiescent state library X-BeenThere: dev@dpdk.org X-Mailman-Version: 2.1.15 Precedence: list List-Id: DPDK patches and discussions <dev.dpdk.org> List-Unsubscribe: <https://mails.dpdk.org/options/dev>, <mailto:dev-request@dpdk.org?subject=unsubscribe> List-Archive: <http://mails.dpdk.org/archives/dev/> List-Post: <mailto:dev@dpdk.org> List-Help: <mailto:dev-request@dpdk.org?subject=help> List-Subscribe: <https://mails.dpdk.org/listinfo/dev>, <mailto:dev-request@dpdk.org?subject=subscribe> X-List-Received-Date: Wed, 28 Nov 2018 05:32:02 -0000 > > > > On Wed, 21 Nov 2018 21:30:52 -0600 > > Honnappa Nagarahalli <honnappa.nagarahalli@arm.com> wrote: > > > > > Lock-less data structures provide scalability and determinism. > > > They enable use cases where locking may not be allowed (for ex: > > > real-time applications). > > > >=20 > <snip detailed RFC commit messag> >=20 > > > Dharmik Thakkar (1): > > > test/tqs: Add API and functional tests > > > > > > Honnappa Nagarahalli (2): > > > log: add TQS log type > > > tqs: add thread quiescent state library > > > > > > config/common_base | 6 + > > > lib/Makefile | 2 + > > > lib/librte_eal/common/include/rte_log.h | 1 + > > > lib/librte_tqs/Makefile | 23 + > > > lib/librte_tqs/meson.build | 5 + > > > lib/librte_tqs/rte_tqs.c | 249 +++++++++++ > > > lib/librte_tqs/rte_tqs.h | 352 +++++++++++++++ > > > lib/librte_tqs/rte_tqs_version.map | 16 + > > > lib/meson.build | 2 +- > > > mk/rte.app.mk | 1 + > > > test/test/Makefile | 2 + > > > test/test/autotest_data.py | 6 + > > > test/test/meson.build | 5 +- > > > test/test/test_tqs.c | 540 ++++++++++++++++++++++= ++ > > > 14 files changed, 1208 insertions(+), 2 deletions(-) create mode > > > 100644 lib/librte_tqs/Makefile create mode 100644 > > > lib/librte_tqs/meson.build create mode 100644 > > > lib/librte_tqs/rte_tqs.c create mode 100644 > > > lib/librte_tqs/rte_tqs.h create mode 100644 > > > lib/librte_tqs/rte_tqs_version.map > > > create mode 100644 test/test/test_tqs.c > > > > > > > Mixed feelings about this one. > > > > Love to see RCU used for more things since it is much better than > > reader/writer locks for many applications. But hate to see DPDK > > reinventing every other library and not reusing code. Userspace RCU > > https://liburcu.org/ is widely supported by distro's, more throughly > > tested and documented, and more flexiple. > > > > The issue with many of these reinventions is a tradeoff of DPDK > > growing another dependency on external library versus using common code= . > > Agree with the dependency issues. Sometimes flexibility also causes confusi= on and features that are not necessarily required for a targeted use case. = I have seen that much of the functionality that can be left to the applicat= ion is implemented as part of the library. I think having it in DPDK will give us control over the amount of capabilit= y this library will have and freedom over changes we would like to make to = such a library. I also view DPDK as one package where all things required f= or data plane development are available. > > For RCU, the big issue for me is the testing and documentation of how > > to do RCU safely. Many people get it wrong! Hopefully, we all will do a better job collectively :) >=20 >=20 > Some notes on liburcu (and my amateur understanding of LGPL, I'm not a > license lawyer :) >=20 > Liburcu is LGPL, which AFAIK means we must dynamically link applications = if > the application code is BSD or other permissive licenses. >=20 > The side effect of this is that urcu function calls must be "real" functi= on calls > and inlining them is not possible. Therefore using liburcu in LGPL mode c= ould > have a performance impact in this case. I expect estimating the performan= ce > cost would be > difficult as its pretty much a case-by-case depending on what you're doin= g in > the surrounding code. >=20 > Generally I'm in favour of using established libraries (particularly for = complex > functionality like RCU) but in this case I think there's a tradeoff with = raw > performance.