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Fri, 22 Jan 2021 13:23:09 +0000 Message-ID: <0374b95d874d2525f4f354de600b62d369068017.camel@oss.nxp.com> Subject: Re: timerfd performances From: Sebastien Laveze To: Sebastian Andrzej Siewior Cc: linux-rt-users@vger.kernel.org Date: Fri, 22 Jan 2021 14:23:06 +0100 In-Reply-To: <20210122123057.72aeag672rh3omcw@linutronix.de> References: <20210122123057.72aeag672rh3omcw@linutronix.de> Content-Type: text/plain; charset="UTF-8" User-Agent: Evolution 3.36.4-0ubuntu1 Content-Transfer-Encoding: 7bit X-Originating-IP: [84.102.252.120] X-ClientProxiedBy: AM9P195CA0022.EURP195.PROD.OUTLOOK.COM (2603:10a6:20b:21f::27) To VI1PR0401MB2671.eurprd04.prod.outlook.com (2603:10a6:800:55::10) MIME-Version: 1.0 X-MS-Exchange-MessageSentRepresentingType: 1 Received: from nxl65009.wbi.nxp.com (84.102.252.120) by AM9P195CA0022.EURP195.PROD.OUTLOOK.COM (2603:10a6:20b:21f::27) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.20.3784.14 via Frontend Transport; Fri, 22 Jan 2021 13:23:08 +0000 X-MS-PublicTrafficType: Email X-MS-Office365-Filtering-HT: Tenant X-MS-Office365-Filtering-Correlation-Id: 35bb6e01-500a-4070-ff66-08d8bed8dc38 X-MS-TrafficTypeDiagnostic: VI1PR04MB4559: X-MS-Exchange-SharedMailbox-RoutingAgent-Processed: True X-Microsoft-Antispam-PRVS: X-MS-Oob-TLC-OOBClassifiers: OLM:9508; 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But note that all timer wake ups would happen there - even the > accumulated case where we have to wake 100 tasks at once. This would > then probably ask for split on SCHED_OTHER vs RT tasks like it is done > for clock_nanosleep(). I didn't know there was a difference in the wakeup mechanism when using clock_nanosleep if the task was RT or not but that makes sense indeed. (just looking at __hrtimer_init_sleeper) So basically, if re-introduced, the ktimersoftd (with a RT priority by default) would only handle the wakeup of RT tasks ? Other non-RT POSIX/timerfd users would still be woken-up by ksoftirqd ? > > Sebastian Thx, Seb