From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-2.8 required=3.0 tests=DKIM_SIGNED,DKIM_VALID, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_PASS,T_DKIMWL_WL_MED, URIBL_BLOCKED,USER_AGENT_GIT autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 18394EB1DCF for ; Thu, 12 Jul 2018 18:19:51 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id C4FCD213A2 for ; Thu, 12 Jul 2018 18:19:50 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=CAVIUMNETWORKS.onmicrosoft.com header.i=@CAVIUMNETWORKS.onmicrosoft.com header.b="RqLUR2Wq" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org C4FCD213A2 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=caviumnetworks.com Authentication-Results: mail.kernel.org; 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Thu, 12 Jul 2018 18:19:42 +0000 From: Yury Norov To: Frederic Weisbecker , Ingo Molnar , Thomas Gleixner Cc: Yury Norov , "Goutham, Sunil" , Chris Metcalf , linux-kernel@vger.kernel.org Subject: [PATCH] nohz: don't kick non-idle CPUs in tick_nohz_full_kick_cpu() Date: Thu, 12 Jul 2018 21:19:22 +0300 Message-Id: <20180712181922.23073-1-ynorov@caviumnetworks.com> X-Mailer: git-send-email 2.17.1 MIME-Version: 1.0 Content-Type: text/plain X-Originating-IP: [50.233.148.155] X-ClientProxiedBy: AM4PR0101CA0061.eurprd01.prod.exchangelabs.com (2603:10a6:200:41::29) To BN7PR07MB4369.namprd07.prod.outlook.com (2603:10b6:406:b4::31) X-MS-PublicTrafficType: Email X-MS-Office365-Filtering-Correlation-Id: 046592d2-21a1-4751-c488-08d5e8240abb X-Microsoft-Antispam: UriScan:;BCL:0;PCL:0;RULEID:(7020095)(4652040)(8989117)(5600053)(711020)(4534165)(4627221)(201703031133081)(201702281549075)(8990107)(2017052603328)(7153060)(7193020);SRVR:BN7PR07MB4369; X-Microsoft-Exchange-Diagnostics: 1;BN7PR07MB4369;3:9kx30iQeS7KRBdPy0Dl9BCYYGX/bNCTiUhWRfkRUnSf+bBjb5XBFYNSzo15rw0bFALQ+7vmNqM2YrkR1mp9kCP+vOnnjoPTDlh+eoRdLGXJInwckj1JCNx5kAw+mdXQcJnc/s7O4LiHDF2EGR7l4OJwkeZoFmPiUDZ5MW03y8iwtw6VUPvO3+gNl43UsafckFglXCrZMmAYdJ0nuRKYyNgeP+UVoAbF5MsyZ79KypkFfalrYFAW+hmL+SfzOmuFv;25:fivKplDMI3vvWCAkvZrdmiBPPFOeS6lHOTZkWDq/uH/NOl4rxaL2P7AATeqBR/jgZjW3WI997jaSscxrNrKOL/06V54NtSZx9Zd9kg2d/A077CCH40HWJ6+Gko+mTqUxoYgbnAKea8QaRBrB+zCFGWbIj1wEQlU9So7lYv0Oe0JmlK3r+haRbVYBNQ6ZYA4uH7Wmzn/8fe8YLtfeydjo8Wjj230ce9Ffgt+/lJb+eo5de2/svOS8mX5h6iYBLpl3z+MKjIIebGt8IU2JdsOZZVC8BM7ySW9CuJC/Oz4LfdftaUN1xpXRgHlauXdlv4jDxzZS/AWWrKDt5BM7/2TXkg==;31:ITn/tA2V5l/BmkTCFiZZbypDK7J7sudfHGHj2e56VbuEU9njMI2BrAmf8rny225aJs7NPmRFuOV482JaqeyTVRs1aoLHBUvB9z3lTt67FMenHmgSOJhzXe1u/XerfZY+kXm2jbUi4sULDHdwb0Aw+HtSERWs8ZUfbFuo0Xq6PtxSXs1BW+cKHP/YyBS9krih7KxTCz6UR5Ps8RimdwjIv6xzZ4fzbh7RC4rOkPGxWNM= X-MS-TrafficTypeDiagnostic: BN7PR07MB4369: X-Microsoft-Exchange-Diagnostics: 1;BN7PR07MB4369;20: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;4:mPvGuSGWO+tURnk9heeeoe+Xz7UxXzQLLLXIMJgSp6veNdR9eG1M+UTVJ8DzpasmleECxkNgcVNuYjnCc1dwkzpXMf/lXYKppZBZydjp7+JAZDW7gufkoDMhI1fcX1cPJwQI4aIozDPG+PrPhbknMRIwR5vp8c81qS8nhvD1pGi0061RC0e7NtSDHfw8uKrLUS9/ydMzoh6BBm8Xi1gFsyQoYM8QScIp5z5flsLWQwHdxDyx1Bp29QNdLghTM7KVCz/AMZjmFXWXjBZembZrgCdn7aH+/mcd4bkOTQXFvw4p0tkcsoaeik2XwMVOSEpp X-Microsoft-Antispam-PRVS: X-Exchange-Antispam-Report-Test: UriScan:(190756311086443); 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But in fact this function kicks all CPUs listed in tick_nohz_full_mask, namely: - idle CPUs; - CPUs runnung normal tasks; - CPUs running isolated tasks [1]; For normal tasks it introduces unneeded latency, and for isolated tasks it's fatal because isolation gets broken and task receives SIGKILL. The patch below makes tick_nohz_full_kick_cpu() kicking only idle CPUs. Non-idle nohz_full CPUs will observe changed system settings just like non-idle normal (i.e. not nohz_full) CPUs, at next reschedule. [1] https://lkml.org/lkml/2017/11/3/589 Signed-off-by: Yury Norov --- kernel/time/tick-sched.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/kernel/time/tick-sched.c b/kernel/time/tick-sched.c index c026145eba2f..1c24c700e75a 100644 --- a/kernel/time/tick-sched.c +++ b/kernel/time/tick-sched.c @@ -247,7 +247,7 @@ static void tick_nohz_full_kick(void) */ void tick_nohz_full_kick_cpu(int cpu) { - if (!tick_nohz_full_cpu(cpu)) + if (!(tick_nohz_full_cpu(cpu) && idle_cpu(cpu))) return; irq_work_queue_on(&per_cpu(nohz_full_kick_work, cpu), cpu); -- 2.17.1