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Mon, 26 Jul 2021 17:53:03 +0000 From: Chuck Lever III To: Tom Talpey CC: Linux NFS Mailing List , "linux-rdma@vger.kernel.org" Subject: Re: [PATCH v1 1/3] svcrdma: Fewer calls to wake_up() in Send completion handler Thread-Topic: [PATCH v1 1/3] svcrdma: Fewer calls to wake_up() in Send completion handler Thread-Index: AQHXgi0aAICH5QRXb0W5AeOWKdTjH6tVeDMAgAARmgA= Date: Mon, 26 Jul 2021 17:53:03 +0000 Message-ID: References: <162731055652.13580.8774661104190191089.stgit@klimt.1015granger.net> <162731081843.13580.15415936872318036839.stgit@klimt.1015granger.net> In-Reply-To: Accept-Language: en-US Content-Language: en-US X-MS-Has-Attach: X-MS-TNEF-Correlator: authentication-results: talpey.com; dkim=none (message not signed) header.d=none;talpey.com; dmarc=none action=none header.from=oracle.com; x-ms-publictraffictype: Email x-ms-office365-filtering-correlation-id: 5e8e02e1-02ef-4e7b-4ce6-08d9505e3728 x-ms-traffictypediagnostic: SJ0PR10MB5534: x-microsoft-antispam-prvs: x-ms-oob-tlc-oobclassifiers: OLM:6430; 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charset="us-ascii" Content-ID: Content-Transfer-Encoding: quoted-printable MIME-Version: 1.0 X-OriginatorOrg: oracle.com X-MS-Exchange-CrossTenant-AuthAs: Internal X-MS-Exchange-CrossTenant-AuthSource: SJ0PR10MB4688.namprd10.prod.outlook.com X-MS-Exchange-CrossTenant-Network-Message-Id: 5e8e02e1-02ef-4e7b-4ce6-08d9505e3728 X-MS-Exchange-CrossTenant-originalarrivaltime: 26 Jul 2021 17:53:03.1425 (UTC) X-MS-Exchange-CrossTenant-fromentityheader: Hosted X-MS-Exchange-CrossTenant-id: 4e2c6054-71cb-48f1-bd6c-3a9705aca71b X-MS-Exchange-CrossTenant-mailboxtype: HOSTED X-MS-Exchange-CrossTenant-userprincipalname: QAqA/i5jaZKwfnLb1+YtpVbW+e6tjO6vExibprptIlLdjlsY66FajAuFZNL2CU72GsH4VKJtKgisRda5lavTDA== X-MS-Exchange-Transport-CrossTenantHeadersStamped: SJ0PR10MB5534 X-Proofpoint-Virus-Version: vendor=nai engine=6200 definitions=10057 signatures=668682 X-Proofpoint-Spam-Details: rule=notspam policy=default score=0 suspectscore=0 bulkscore=0 phishscore=0 malwarescore=0 spamscore=0 mlxlogscore=999 mlxscore=0 adultscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2104190000 definitions=main-2107260104 X-Proofpoint-ORIG-GUID: 1c0stp2ZQDC9cLbk6riE4W2VxTgDG9SD X-Proofpoint-GUID: 1c0stp2ZQDC9cLbk6riE4W2VxTgDG9SD Precedence: bulk List-ID: X-Mailing-List: linux-rdma@vger.kernel.org > On Jul 26, 2021, at 12:50 PM, Tom Talpey wrote: >=20 > On 7/26/2021 10:46 AM, Chuck Lever wrote: >> /** >> * svc_rdma_wc_send - Invoked by RDMA provider for each polled Send WC >> * @cq: Completion Queue context >> @@ -275,11 +289,9 @@ static void svc_rdma_wc_send(struct ib_cq *cq, stru= ct ib_wc *wc) >> trace_svcrdma_wc_send(wc, &ctxt->sc_cid); >> + svc_rdma_wake_send_waiters(rdma, 1); >> complete(&ctxt->sc_done); >> - atomic_inc(&rdma->sc_sq_avail); >> - wake_up(&rdma->sc_send_wait); >=20 > This appears to change the order of wake_up() vs complete(). > Is that intentional? IIRC I reversed the order here to be consistent with the other Send completion handlers. > Is there any possibility of a false > scheduler activation, later leading to a second wakeup or poll? The two "wake-ups" here are not related to each other, and RPC Replies are transmitted already so this shouldn't have a direct impact on server latency. But I might not understand your question. -- Chuck Lever