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 Received: from lists.xenproject.org (lists.xenproject.org [192.237.175.120]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id C278CCD98DA for ; Tue, 16 Jun 2026 06:48:04 +0000 (UTC) Received: from list by lists.xenproject.org with outflank-mailman.1338680.1599711 (Exim 4.92) (envelope-from ) id 1wZNaM-0001Fc-Cm; Tue, 16 Jun 2026 06:47:46 +0000 X-Outflank-Mailman: Message body and most headers restored to incoming version Received: by outflank-mailman (output) from mailman id 1338680.1599711; Tue, 16 Jun 2026 06:47:46 +0000 Received: from localhost ([127.0.0.1] helo=lists.xenproject.org) by lists.xenproject.org with esmtp (Exim 4.92) (envelope-from ) id 1wZNaM-0001FV-AA; Tue, 16 Jun 2026 06:47:46 +0000 Received: by outflank-mailman (input) for mailman id 1338680; Tue, 16 Jun 2026 06:47:45 +0000 Received: from mx.expurgate.net ([195.190.135.10]) by lists.xenproject.org with esmtp (Exim 4.92) (envelope-from ) id 1wZNaK-0001DS-QM for xen-devel@lists.xenproject.org; Tue, 16 Jun 2026 06:47:45 +0000 Received: from mx.expurgate.net (helo=localhost) by mx.expurgate.net with esmtp id 1wZNaJ-004MxQ-JO for xen-devel@lists.xenproject.org; Tue, 16 Jun 2026 08:47:43 +0200 Received: from [10.42.69.9] (helo=localhost) by localhost with ESMTP (eXpurgate MTA 0.9.1) (envelope-from ) id 6a30f18c-bab6-0a2a0a5309dd-0a2a4509d934-12 for ; Tue, 16 Jun 2026 08:47:43 +0200 Received: from [40.107.209.19] (helo=PH8PR06CU001.outbound.protection.outlook.com) by tlsNG-bad1c0.mxtls.expurgate.net with ESMTPS (eXpurgate 4.56.1) (envelope-from ) id 6a30f18d-2497-0a2a45090019-286bd113a059-3 for ; Tue, 16 Jun 2026 08:47:43 +0200 Received: from CH7PR03MB7860.namprd03.prod.outlook.com (2603:10b6:610:24e::14) by SA1PR03MB6548.namprd03.prod.outlook.com (2603:10b6:806:1c7::20) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.21.113.18; Tue, 16 Jun 2026 06:47:39 +0000 Received: from CH7PR03MB7860.namprd03.prod.outlook.com ([fe80::f5ba:35df:1c9f:b343]) by CH7PR03MB7860.namprd03.prod.outlook.com ([fe80::f5ba:35df:1c9f:b343%4]) with mapi id 15.21.0113.015; Tue, 16 Jun 2026 06:47:39 +0000 X-BeenThere: xen-devel@lists.xenproject.org List-Id: Xen developer discussion List-Unsubscribe: , List-Post: List-Help: List-Subscribe: , Errors-To: xen-devel-bounces@lists.xenproject.org Precedence: list Sender: "Xen-devel" Authentication-Results: eu.smtp.expurgate.cloud; dkim=pass header.s=selector1 header.d=citrix.com header.i="@citrix.com" header.h="From:Date:Subject:Message-ID:Content-Type:MIME-Version:X-MS-Exchange-SenderADCheck" ARC-Seal: i=1; a=rsa-sha256; s=arcselector10001; d=microsoft.com; cv=none; b=dgOhQPIRpd1E7RV8kcHYgwiru6HKbHCIOX+nJMfxspLAwSq+DP8HiQbD07EypV8g5EhvENlt78DPZi7O2xAf+tvGBoFAbMoxr0zbr+Z1xfRZT+9pFu8nat1XudENim6RfpRtY74KCG641b+tsaVwW711NInvszXaweeaBRnpRb/yMfKGl1ncdORNNKLj+zHox5qBhtdG1XU3/1ctvjqnGrVNtCcoqVZph4pU56KLykry7O4DA8iDeT2W/wqLVQWxl+w+IT8z7uo20pmEb2f9A7mjanTvjIULRJbtLfPq6hG+YZSoxJRCdCRuaZcbPrShPiPSTIs2fWWn+WaEEaIFzA== ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=microsoft.com; s=arcselector10001; h=From:Date:Subject:Message-ID:Content-Type:MIME-Version:X-MS-Exchange-AntiSpam-MessageData-ChunkCount:X-MS-Exchange-AntiSpam-MessageData-0:X-MS-Exchange-AntiSpam-MessageData-1; bh=zn2S0ajeUitG6erztRvDBXWugCanY7dAJEDOOBeN9SY=; b=ta7Ha3rf7zRJL4Lo2WhBjpiyYUtfxUvlIF7+eBlTgF3HxCswpp4oELWrBjkdnK07LsJot5MUneRsX4uOS92PYq+rZXTaSAUDamGOlqJoUhWsAHtMBJG8yoMA/b8gnsuwGi3VilVvDorLw7TNJWCagy7PqFru6JPkZNPiOlGIemf5IkBPSmpwmWWy3+oBCxQgQHfD5WxwtiCQzTgw2gjJJmIlx61ld5FgENEk5neum8FktjrCoot0eLRerx1f7NODtuOHpBYUImsyvuboIUPv3T80x7zp8pfjjvoaLgjubMH+qJNqceu4+wiRpcsFObigPUhj2QsBKWNYwWBKCQv9TQ== ARC-Authentication-Results: i=1; mx.microsoft.com 1; spf=pass smtp.mailfrom=citrix.com; dmarc=pass action=none header.from=citrix.com; dkim=pass header.d=citrix.com; arc=none DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=citrix.com; s=selector1; h=From:Date:Subject:Message-ID:Content-Type:MIME-Version:X-MS-Exchange-SenderADCheck; bh=zn2S0ajeUitG6erztRvDBXWugCanY7dAJEDOOBeN9SY=; b=Eoy8cMi5V7avJmoU1INZq2p+x6DHjDD9B/4VAAM2TXovq5IzfMcWlBg8Dz0RH7ZWFp98Moq8oVcOPzgQOmNKKSWXIwRmE8LMndu2iGN9pni8FnKQATIANjTGqUfrVwhOveuYSq9QF9omXfH8qcIKwIDxwBVHz0W2uJsO5ITyyMQ= Authentication-Results: dkim=none (message not signed) header.d=none;dmarc=none action=none header.from=citrix.com; Date: Tue, 16 Jun 2026 08:47:34 +0200 From: Roger Pau =?utf-8?B?TW9ubsOp?= To: Jan Beulich , oleksii.kurochko@gmail.com Cc: Jason Andryuk , xen-devel@lists.xenproject.org Subject: Re: [PATCH for-4.22] Revert "xen/cpufreq: fix usages of align_timer() in the on-demand governor" Message-ID: References: <20260615193944.19392-1-jason.andryuk@amd.com> <1fbb67ab-09f3-4924-b6aa-139fc5d1acc7@suse.com> Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <1fbb67ab-09f3-4924-b6aa-139fc5d1acc7@suse.com> X-ClientProxiedBy: MR1P264CA0008.FRAP264.PROD.OUTLOOK.COM (2603:10a6:501:2e::13) To CH7PR03MB7860.namprd03.prod.outlook.com (2603:10b6:610:24e::14) MIME-Version: 1.0 X-MS-PublicTrafficType: Email X-MS-TrafficTypeDiagnostic: CH7PR03MB7860:EE_|SA1PR03MB6548:EE_ X-MS-Office365-Filtering-Correlation-Id: 3ea9c72d-c15e-4819-3cd1-08decb732819 X-MS-Exchange-SenderADCheck: 1 X-MS-Exchange-AntiSpam-Relay: 0 X-Microsoft-Antispam: BCL:0;ARA:13230040|1800799024|366016|376014|23010399003|18002099003|22082099003|11063799006|4143699003|56012099006; X-Microsoft-Antispam-Message-Info: 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 X-Forefront-Antispam-Report: CIP:255.255.255.255;CTRY:;LANG:en;SCL:1;SRV:;IPV:NLI;SFV:NSPM;H:CH7PR03MB7860.namprd03.prod.outlook.com;PTR:;CAT:NONE;SFS:(13230040)(1800799024)(366016)(376014)(23010399003)(18002099003)(22082099003)(11063799006)(4143699003)(56012099006);DIR:OUT;SFP:1101; X-MS-Exchange-AntiSpam-MessageData-ChunkCount: 1 X-MS-Exchange-AntiSpam-MessageData-0: =?utf-8?B?MkVjQytQbWZZRlNVaCtXdjJOVFNCY28vTGZWQUpKU2ZNRE16QStkN0p4ZnA3?= =?utf-8?B?Z1FQSFhuTlVYWUM1czJwY2dacXZaekk2aEl0YjJTUkZEMUZUVWhFeVY3bFZJ?= =?utf-8?B?NDFGSHdrSUZ0V3NiSmRTZkpSN05hbHkweFNDa043S1owU0xsQXVUNUR5M3lx?= =?utf-8?B?VmhiZ2xuNzhDOE0zTURnajVzdVg0d3hIK09MNHRBY3BDbGxHQURPUEhBWGxj?= =?utf-8?B?dTRjODQxWDhlU1BScFRCK0xjUnE3L1VLVmNxNmJuZGx0blpWSEwrNFE5NS9K?= =?utf-8?B?WTVCaVlodFBhQW42enFRcW43bTQ4b1I5MHIwOEljN29BYVd1UGRTcEszT3BX?= =?utf-8?B?MkFOOVBrck4yakJ6V1dNdDhpb3IxaHdiakZ1VUtCdjJMaVp4bjl2Q0xGUm1x?= =?utf-8?B?emh0OWxGZENCakd4b0JJMWVEeDdMa09WMmQvV1A4dW16djhyREdUVTVMbGQ1?= =?utf-8?B?Sk1Va3lNRFR1Q2FhbWNRZ2o2UlJmclVUekxoelJtSExIVmljL1VKNzhEajRn?= =?utf-8?B?UDROMkFBcnBiTmNCbEEyL1hLa2JVS2JLbkl0cHJZK0N0NEs2S0Q3cFkxc2pa?= =?utf-8?B?bEZjMEdpcjFjWEZCL0kvS3BCSGdoVURJU2hSTHo2Nmgvc051bUNaeWsxQnUv?= =?utf-8?B?am1KbkNiQ1hnWC9ENjU0dGlaUEF1M0Y4aklibkNPRHJFcEdUQXYyNEZzNDFm?= =?utf-8?B?ODRWNWFJTUhWT2tFaUh5VEYxVzRZd0Fxb1lMR3Q1alFNOUpkdk05dW1QTjI5?= =?utf-8?B?c0Vja3F5QnlTRkhSTE1wZFBlNmlQWGdLSi9CYzhRZ21Jb3ppbHlPZjBZcHpZ?= =?utf-8?B?QTA0cmN4OStkZldHZXVWNldZM0svUWhvcTErYkRzS1VpaWQ2c2JSU0pQMjNW?= =?utf-8?B?MXdsQy80VTlad2hNUzFPRjdTbHo1Y1NVSUJRLzdCc0FrZHVQSUpoWlRGUjFV?= =?utf-8?B?a0dTbm5kZzhNMUNZVkdYTHBJM2Fyckh4bDBuV3hWZFBPa1ZOTkFrbXpvY3Iy?= =?utf-8?B?emdKR1cyQWVNWDJ3MkVERkJWeEo4TTYzYS9CT2hEYlM2amQ1d0NIZlY4MzlP?= =?utf-8?B?VkRjTFNWWnMxMUtPWGp1d25nUXdvY2FJRlBvS05sL2hJZlFqMU1ZVjl2bWtZ?= =?utf-8?B?Y1VkaU1OdFVVT0tvS21TMzRQcm1uU0RYSXQxcHBLSit0RUlLWGQwSm1wKzB1?= =?utf-8?B?TEQ0Nk9NdlJRTWtZRlFKODBzZmE0Z3BlM2taU2FjOWZrRzRDQzUyaUdZczlm?= =?utf-8?B?SnNUL2FkWTBsZ1JiSTkyV05ibGxWOExicWk3Ui9pYThjOGRJcmZKRkUvSDhk?= =?utf-8?B?MGR2WDg4MDVZb0RSWUFTbEszMlRqVksvMzRDdThmVnZOWlZGNE1DZVA4dEE5?= =?utf-8?B?eG5SbHlKN2JEeVVtMXhmS3l6a2tIR0ZPcHpseGdyK05qT2VEMnBsbW9NeGM1?= =?utf-8?B?RGNXMEZyemsweEpOYjVDaE8yek04MG1GaXhWSzNmY1RnSzRDRTRpemVDR05L?= =?utf-8?B?UGNKamhOaUZyemIzMFBGM2tka1NvWTFkMVBoNllPYTNmTW1vSTlwM3EzN29H?= =?utf-8?B?cDZLLzg4ZlRXSGt5TU5KZFArUEN1aDJnUE16MDVzdmE2NmphMVFmMlNUalFv?= =?utf-8?B?NzgrRkVNZ3Q1eEQxNkwvVFIvUGZGYnhuNzcrWDhkbTRmOXdBeFZKdWtQOWph?= =?utf-8?B?NzR2Vjh3eEc0MEd3TTlFTDhVN1lVMWQ4dUZRSXBmUW5jaUlJM2Y0NE14NzI1?= =?utf-8?B?U25mb2Y3RHFJMDZaQkt1MnREd2REZnVlNkZ5VHh5TVdYYWdSUTg0Vm9mUUxO?= =?utf-8?B?WnNaMXU3K0t5bjhVY0lwMmdlMFBnT2luUEhqekNTN0paUzIrZlFqQ2tHWHk4?= =?utf-8?B?cytpYis5UmNNSkxkZFUwVkxGdVZrRjBWbFNHeER5S3ZiUHRMY3k1ZG1zcVk4?= =?utf-8?B?dXpZQ1Y4ejVqbVhHREJuS3RsdFVFa2ZaNnd3QVlodFUvZFF6TTZWWUJuSFlp?= =?utf-8?B?TnBrejVWaUVmVlFFamNGMWtlQkhjVUh0L1k5RkwzeTFmdjkraktCT2Y2OWFY?= =?utf-8?B?Zm9ObEF6RFJiV1hqQ3RzVGZrVlpkVytRZXVOaDVGTWxPS2xHL1E3RHEwK1Rt?= =?utf-8?B?OFFSNUMzUHJZb3RTNGdaNHJJY2Y4K29CZ2Jqc2kyMUJXSXF3K01RamNQNjJt?= =?utf-8?B?bW9YbkxJcDdYc0lla1E4cXJKdUJ3cHZaR3l1bDk1czVOdHFvYXVVYm9MeVUz?= =?utf-8?B?L3pHai9ueTE4ZWsvaGQ4dHRxTmJiV1RLOEU2ZmN6N0phL0Jxc2tDcjQ2b2VH?= =?utf-8?B?MG9xRjhneXM5NEpBZThzeXlsVXRma1ZwUDJ4TExJSWdZR1kra2ozUT09?= X-OriginatorOrg: citrix.com X-MS-Exchange-CrossTenant-Network-Message-Id: 3ea9c72d-c15e-4819-3cd1-08decb732819 X-MS-Exchange-CrossTenant-AuthSource: CH7PR03MB7860.namprd03.prod.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Internal X-MS-Exchange-CrossTenant-OriginalArrivalTime: 16 Jun 2026 06:47:38.9665 (UTC) X-MS-Exchange-CrossTenant-FromEntityHeader: Hosted X-MS-Exchange-CrossTenant-Id: 335836de-42ef-43a2-b145-348c2ee9ca5b X-MS-Exchange-CrossTenant-MailboxType: HOSTED X-MS-Exchange-CrossTenant-UserPrincipalName: bOPZGmeNtbl9LNToeoo3kof1BfOCADnOEtkbUM3Il4mMVBnsMvmpOAuAeYvWSFyhwqrxsM4wrcYIb+JOMaOPlA== X-MS-Exchange-Transport-CrossTenantHeadersStamped: SA1PR03MB6548 X-purgate-ID: tlsNG-bad1c0/1781592463-8A788A53-B8429192/0/0 X-purgate-type: clean X-purgate-size: 2780 On Tue, Jun 16, 2026 at 08:30:25AM +0200, Jan Beulich wrote: > On 15.06.2026 21:39, Jason Andryuk wrote: > > The original commit showed a ~6% regression in a benchmark. The call to > > align_timer(firsttick, period) rounds firsttick up to the next mutiple > > of the period, if firsttick % period != 0: > > > > align_timer(0, period) -> 0 > > align_timer(1, period) -> period > > align_timer(period, period) -> period > > align_timer(period + 1, period) -> 2 * period > > > > So adding the period (sampling_rate) before calling align_timer() will > > in most cases incease the expiration to 2 * period (sampling_rate) (the > > exception being firsttick % period == 0). This longer timer slows the > > reaction time of the algorithm. > > > > This reverts commit a0ed5bcfbeee81c91c574ad484faa057054eaf09. > > > > Signed-off-by: Jason Andryuk Acked-by: Roger Pau Monné Adding Oleksii for a release-ack. > > --- > > This is backported in stable trees and should be reverted there as well > > (found in 4.20.3). > > > > A Fixes seems superfluous and not normally used with a revert, but if > > needed: > > Fixes: a0ed5bcfbeee ("xen/cpufreq: fix usages of align_timer() in the on-demand governor") > > If "git grep" is intended to (also) find such straight reverts by merely > matching "Fixes: ", I think the tag should still be put there. > > Talking of Fixes: tags - the original change had two of them, so there > must have been a problem? Or, Roger, was this purely an observation from > looking the the code? It was purely by observation that the current timer setup will very likely fire before the set period, making the sampling intervals possibly shorter. However shorter periods are fine, we simply over-sample. Longer periods as shown by Jason have an adverse impact in the response time of the governor. > > --- a/xen/drivers/cpufreq/cpufreq_ondemand.c > > +++ b/xen/drivers/cpufreq/cpufreq_ondemand.c > > @@ -185,8 +185,7 @@ static void cf_check do_dbs_timer(void *dbs) > > dbs_check_cpu(dbs_info); > > > > set_timer(&per_cpu(dbs_timer, dbs_info->cpu), > > - align_timer(NOW() + dbs_tuners_ins.sampling_rate, > > - dbs_tuners_ins.sampling_rate)); > > + align_timer(NOW() , dbs_tuners_ins.sampling_rate)); > > } > > As much as I understand you wanting to have things simple by doing a > straight revert, imo the formatting flaws better wouldn't be introduced > again. If I ended up committing this, I'd very likely take the liberty > of doing so. Yet before ack-ing the question above needs answering. I wouldn't mind adjusting this at commit. Thanks, Roger.