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[23.128.96.36]) by mx.google.com with ESMTPS id bm1-20020a656e81000000b005c626128e67si10250605pgb.494.2023.12.05.04.12.40 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 05 Dec 2023 04:12:41 -0800 (PST) Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 23.128.96.36 as permitted sender) client-ip=23.128.96.36; Authentication-Results: mx.google.com; spf=pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 23.128.96.36 as permitted sender) smtp.mailfrom=linux-kernel-owner@vger.kernel.org; dmarc=pass (p=NONE sp=NONE dis=NONE) header.from=kernel.org Received: from out1.vger.email (depot.vger.email [IPv6:2620:137:e000::3:0]) by pete.vger.email (Postfix) with ESMTP id 6C8ED8133F83; Tue, 5 Dec 2023 04:12:38 -0800 (PST) X-Virus-Status: Clean X-Virus-Scanned: clamav-milter 0.103.11 at pete.vger.email Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231912AbjLEMMQ convert rfc822-to-8bit (ORCPT + 99 others); Tue, 5 Dec 2023 07:12:16 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:40016 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231871AbjLEMMQ (ORCPT ); Tue, 5 Dec 2023 07:12:16 -0500 Received: from mail-oa1-f54.google.com (mail-oa1-f54.google.com [209.85.160.54]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id BBE6AC3 for ; Tue, 5 Dec 2023 04:12:22 -0800 (PST) Received: by mail-oa1-f54.google.com with SMTP id 586e51a60fabf-1fb1620a00eso710839fac.1 for ; Tue, 05 Dec 2023 04:12:22 -0800 (PST) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1701778342; x=1702383142; h=content-transfer-encoding:cc:to:subject:message-id:date:from :in-reply-to:references:mime-version:x-gm-message-state:from:to:cc :subject:date:message-id:reply-to; bh=K1huvNNeQ9UeMMl5w2SdOEQfS8q+089rdbok3L8xrR0=; b=UTXxrwthkVwsfnbocwFp42bZ3ecSiNZZqcZVPlAJo0Jecor1F2VokNkEIiIPt0bKMM 5EtwBFN0Tbt780PgdnjqIYx34JJA+UfNXR1wQ0loRLsP6L9Krr+to2t1wy5OC6xbyVsW e1SMDi2tU3y2l7fPL2xXNVXM3OGYU9qLwXveksQKY8AncPrZR03PuT+Hqvq8Ohp8PWd2 abbrS4HqvYGu2rc9D2PI5OAkTXSBZQNow5xJw9b4H/XdYNmEglSVCBXW9ZmcUgdwjUkN edjR63KfxY/3RKKTxLgqtGwAyBp0WfdnCpzv3H2fw+sDA999KZMi809LX85V7KZXWb/k Qtpw== X-Gm-Message-State: AOJu0Yzzhq6nu6whIK4g5NN4pEBgVYgQM07XdsaVcm+CgSEhT3vJ4Gd6 GX4WA4o4NwP7jWdKRm0h3R5SAlB78JfOxrnO0fc= X-Received: by 2002:a05:6870:b60c:b0:1fb:5d05:685e with SMTP id cm12-20020a056870b60c00b001fb5d05685emr2893332oab.2.1701778342010; Tue, 05 Dec 2023 04:12:22 -0800 (PST) MIME-Version: 1.0 References: <53bce76c5c60463eba1372df426a64b9@amazon.co.uk> <1D71D218-5EB6-47DE-A01B-3A66F9F4C74E@infradead.org> In-Reply-To: <1D71D218-5EB6-47DE-A01B-3A66F9F4C74E@infradead.org> From: "Rafael J. Wysocki" Date: Tue, 5 Dec 2023 13:12:09 +0100 Message-ID: Subject: Re: [PATCH] x86: intel_epb: Add earlyparam option to keep bias at performance To: David Woodhouse Cc: pdurrant@amazon.co.uk, bp@alien8.de, dave.hansen@intel.com, dave.hansen@linux.intel.com, hdegoede@redhat.com, hpa@zytor.com, jalliste@amazon.co.uk, juew@amazon.com, len.brown@intel.com, linux-kernel@vger.kernel.org, mingo@redhat.com, peterz@infradead.org, rafael.j.wysocki@intel.com, rafael@kernel.org, tglx@linutronix.de, usama.arif@bytedance.com, x86@kernel.org Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: 8BIT X-Spam-Status: No, score=-1.0 required=5.0 tests=MAILING_LIST_MULTI, SPF_HELO_NONE,SPF_PASS,T_SCC_BODY_TEXT_LINE autolearn=unavailable autolearn_force=no version=3.4.6 X-Spam-Checker-Version: SpamAssassin 3.4.6 (2021-04-09) on pete.vger.email Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org X-Greylist: Sender passed SPF test, not delayed by milter-greylist-4.6.4 (pete.vger.email [0.0.0.0]); Tue, 05 Dec 2023 04:12:38 -0800 (PST) On Tue, Dec 5, 2023 at 1:00 PM David Woodhouse wrote: > > > Paul writes: > > The problem is that this will take effect even on a kexec and hence it is throttling > > a system that set ENERGY_PERF_BIAS_PERFORMANCE prior to the kexec. We use kexec to > > live update the host kernel of our systems whilst leaving virtual machines running. > > This resetting of the perf bias is having a very detrimental effect on the downtime > > of our systems across the live update - about a 7 fold increase. > > It isn't just about kexec, is it? Even in a clean boot why wouldn't we want to stay in performance mode until the kernel has *finished* booting? Because it may overheat during that period. > It's literally adding seconds to the startup time in some cases. > > And yes, we *particularly* care in the kexec case because guests experience it as excessive steal time. But it ain't great in the general case either, surely? So IMV it would be perfectly fine to add a command line arg to provide the initial value of energy_perf_bias for the ones who know what they are doing.