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 vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 07F64C433EF for ; Tue, 28 Jun 2022 16:44:00 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231889AbiF1Qnc (ORCPT ); Tue, 28 Jun 2022 12:43:32 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:54762 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S235162AbiF1QmO (ORCPT ); Tue, 28 Jun 2022 12:42:14 -0400 Received: from mga04.intel.com (mga04.intel.com [192.55.52.120]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id C064FCD4; Tue, 28 Jun 2022 09:39:53 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=intel.com; i=@intel.com; q=dns/txt; s=Intel; t=1656434393; x=1687970393; h=from:to:cc:subject:date:message-id:references: in-reply-to:content-transfer-encoding:mime-version; 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Tue, 28 Jun 2022 09:39:31 -0700 Received: from fmsmsx610.amr.corp.intel.com (10.18.126.90) by fmsmsx612.amr.corp.intel.com (10.18.126.92) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256) id 15.1.2308.27; Tue, 28 Jun 2022 09:39:31 -0700 Received: from fmsmsx610.amr.corp.intel.com ([10.18.126.90]) by fmsmsx610.amr.corp.intel.com ([10.18.126.90]) with mapi id 15.01.2308.027; Tue, 28 Jun 2022 09:39:31 -0700 From: "Luck, Tony" To: "tarumizu.kohei@fujitsu.com" , 'Linus Walleij' CC: Greg KH , "catalin.marinas@arm.com" , "will@kernel.org" , "tglx@linutronix.de" , "mingo@redhat.com" , "bp@alien8.de" , "dave.hansen@linux.intel.com" , "x86@kernel.org" , "hpa@zytor.com" , "rafael@kernel.org" , "lenb@kernel.org" , "mchehab+huawei@kernel.org" , "eugenis@google.com" , "pcc@google.com" , "peterz@infradead.org" , "marcos@orca.pet" , "marcan@marcan.st" , "nicolas.ferre@microchip.com" , "conor.dooley@microchip.com" , "arnd@arndb.de" , "ast@kernel.org" , "peter.chen@kernel.org" , "kuba@kernel.org" , "linux-kernel@vger.kernel.org" , "linux-arm-kernel@lists.infradead.org" , "linux-acpi@vger.kernel.org" Subject: RE: [PATCH v5 0/6] Add hardware prefetch control driver for A64FX and x86 Thread-Topic: [PATCH v5 0/6] Add hardware prefetch control driver for A64FX and x86 Thread-Index: AQHYemdOe4e+BwzSVEeUnZkOYa/FOK1JFpkAgAY1RYCAAArrgIAEgNwAgA+7kYCAAdqygP//t3Xw Date: Tue, 28 Jun 2022 16:39:31 +0000 Message-ID: References: <20220607120530.2447112-1-tarumizu.kohei@fujitsu.com> In-Reply-To: Accept-Language: en-US Content-Language: en-US X-MS-Has-Attach: X-MS-TNEF-Correlator: dlp-product: dlpe-windows dlp-reaction: no-action dlp-version: 11.6.500.17 msip_labels: =?utf-8?B?TVNJUF9MYWJlbF9hNzI5NWNjMS1kMjc5LTQyYWMtYWI0ZC0zYjBmNGZlY2Uw?= =?utf-8?B?NTBfQWN0aW9uSWQ9NzBjY2M1ODgtNDljNi00ZGUxLWJhMmQtMDIyYzBmYmZl?= =?utf-8?B?OWYzO01TSVBfTGFiZWxfYTcyOTVjYzEtZDI3OS00MmFjLWFiNGQtM2IwZjRm?= =?utf-8?B?ZWNlMDUwX0NvbnRlbnRCaXRzPTA7TVNJUF9MYWJlbF9hNzI5NWNjMS1kMjc5?= =?utf-8?B?LTQyYWMtYWI0ZC0zYjBmNGZlY2UwNTBfRW5hYmxlZD10cnVlO01TSVBfTGFi?= =?utf-8?B?ZWxfYTcyOTVjYzEtZDI3OS00MmFjLWFiNGQtM2IwZjRmZWNlMDUwX01ldGhv?= =?utf-8?B?ZD1TdGFuZGFyZDtNU0lQX0xhYmVsX2E3Mjk1Y2MxLWQyNzktNDJhYy1hYjRk?= =?utf-8?B?LTNiMGY0ZmVjZTA1MF9OYW1lPUZVSklUU1UtUkVTVFJJQ1RFRO+/ou++gA==?= =?utf-8?B?776LO01TSVBfTGFiZWxfYTcyOTVjYzEtZDI3OS00MmFjLWFiNGQtM2IwZjRm?= =?utf-8?B?ZWNlMDUwX1NldERhdGU9MjAyMi0wNi0yOFQxMzo0MDo0NFo7TVNJUF9MYWJl?= =?utf-8?B?bF9hNzI5NWNjMS1kMjc5LTQyYWMtYWI0ZC0zYjBmNGZlY2UwNTBfU2l0ZUlk?= =?utf-8?Q?=3Da19f121d-81e1-4858-a9d8-736e267fd4c7;?= x-originating-ip: [10.1.200.100] Content-Type: text/plain; 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charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org >> The right way to solve this is to make the Linux kernel contain the necessary >> heuristics to identify which tasks and thus cores need this to improve efficiency >> and then apply it automatically. >> >> Putting it in userspace is making a human do a machines job which isn't >> sustainable. >> >> By putting the heuristics in kernelspace Linux will improve performance also on >> workloads the human operator didn't think of as the machine will detect them from >> statictical or other behaviour patterns. > >In order to put the heuristics into kernelspace Linux, I think it >necessary to consider the following two points. > >1) Which cores are tied with the process? >This is different from the core on which the process can run. It >probably need to combine some CPU resource limit to avoid affecting >non-target processes. > >2) How to derive the value to set in the register? >It is necessary to verify whether an appropriate set value can be >derived using statistical information, etc. In addition, to prevent >the cost of automatic derivation from exceeding the value that would >be improved by it. > >I don't have a prospect for resolving these issues yet. I will >continue these considerations. Another approach would be to make the set of prefetch settings a task attribute. Then set them in the context switch code when the process is about to run on a CPU. But that assumes you can cheaply change the attributes. If doing so requires multiple MSR writes (on x86) it might be a non-starter. -Tony _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel