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Thu, 30 Jan 2020 23:10:16 +0000 From: Rick Macklem To: freebsd-net Subject: NFS performance depends on low latency reception of small TCP segments Thread-Topic: NFS performance depends on low latency reception of small TCP segments Thread-Index: AQHV18GQFrKXcHa270y7CKj+bcj9Ug== Date: Thu, 30 Jan 2020 23:10:16 +0000 Message-ID: Accept-Language: en-US Content-Language: en-US X-MS-Has-Attach: X-MS-TNEF-Correlator: x-ms-publictraffictype: Email x-ms-office365-filtering-correlation-id: a14bbe21-5293-4f7e-576a-08d7a5d9916d x-ms-traffictypediagnostic: YTBPR01MB2416: x-microsoft-antispam-prvs: x-ms-oob-tlc-oobclassifiers: OLM:9508; x-forefront-prvs: 02981BE340 x-forefront-antispam-report: SFV:NSPM; SFS:(10009020)(366004)(189003)(199004)(8936002)(4744005)(8676002)(81166006)(81156014)(6916009)(26005)(2906002)(186003)(6506007)(5660300002)(9686003)(52536014)(7696005)(86362001)(66446008)(76116006)(71200400001)(33656002)(55016002)(498600001)(64756008)(66476007)(66556008)(66946007)(91956017); DIR:OUT; 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R_SPF_ALLOW(-0.20)[+ip4:40.107.0.0/16]; TO_MATCH_ENVRCPT_ALL(0.00)[]; MIME_GOOD(-0.10)[text/plain]; DMARC_NA(0.00)[uoguelph.ca]; NEURAL_HAM_LONG(-1.00)[-1.000,0]; RCPT_COUNT_ONE(0.00)[1]; RCVD_COUNT_THREE(0.00)[3]; IP_SCORE(-1.39)[ipnet: 40.64.0.0/10(-3.85), asn: 8075(-3.06), country: US(-0.05)]; TO_DN_ALL(0.00)[]; RCVD_IN_DNSWL_NONE(0.00)[60.66.107.40.list.dnswl.org : 127.0.3.0]; FROM_EQ_ENVFROM(0.00)[]; R_DKIM_NA(0.00)[]; MIME_TRACE(0.00)[0:+]; ASN(0.00)[asn:8075, ipnet:40.64.0.0/10, country:US]; ARC_ALLOW(-1.00)[i=1] X-BeenThere: freebsd-net@freebsd.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Networking and TCP/IP with FreeBSD List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Thu, 30 Jan 2020 23:10:19 -0000 Hi,=0A= =0A= I have seen recent discussion related to NET_EPOCH.=0A= This is way out of my expertise, but...=0A= =0A= NFS traffic is basically bi-directional small messages.=0A= If a change increases the latency of reception of a small=0A= message (TCP segment) which is not followed by further=0A= TCP segments in the same direction...=0A= --> A significant NFS performance hit could be observed.=0A= =0A= I don't have hardware that can do reasonable benchmarking,=0A= so if some else can test for NFS performance regressions=0A= when making TCP stack changes, it would be appreciated.=0A= --> The time it takes to do a fairly large build like a kernel=0A= or buildworld over NFS on fast hardware with fast networking=0A= would probably do it.=0A= =0A= Just wanted the people doing TCP stack work to be aware of this, rick=0A=