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 F23A7C6FA82 for ; Thu, 22 Sep 2022 18:18:26 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S232397AbiIVSSZ (ORCPT ); Thu, 22 Sep 2022 14:18:25 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:57498 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S232392AbiIVSSY (ORCPT ); Thu, 22 Sep 2022 14:18:24 -0400 Received: from mga14.intel.com (mga14.intel.com [192.55.52.115]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id D86D910912A; Thu, 22 Sep 2022 11:18:22 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=intel.com; i=@intel.com; q=dns/txt; s=Intel; t=1663870703; x=1695406703; h=message-id:date:mime-version:subject:to:cc:references: from:in-reply-to:content-transfer-encoding; bh=irvpxRGJNiroM1fXkhuMmUhHwaH1jS9Bj7zSfZHS2YY=; b=anQvo6aPXHB1/aXMtMyd2JhzZviW6g3lc23KwKyZHqzdKSdTEPKTQGyc /QUrg3MVohEdIgsoUSxWACnfkHD24Tjr3jYOLCSmGPf65zsiMD2kRZFZb UywDvHf0/Ed+U2S2QM5zsc2VWBTi8K7qHDmblp08c0InFBL5AlrkwVDyy 9Ndx6C6EQkgq+eWaspsmTNj0sWts8YfG08UGd3lP5o1bp7mU5igLiPqvz IFzo5c18+js1u1+oaB7LtQJf7LaE5qhz/0orqiUcsjd5sCwecoxcjX2Pl 9fmAms5qGgHCCPoTsJi7qaMUAL3TnwGEpvNg4f/2STOLDzoydUuLmOH4R Q==; X-IronPort-AV: E=McAfee;i="6500,9779,10478"; a="300371015" X-IronPort-AV: E=Sophos;i="5.93,337,1654585200"; d="scan'208";a="300371015" Received: from fmsmga008.fm.intel.com ([10.253.24.58]) by fmsmga103.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 22 Sep 2022 11:17:55 -0700 X-IronPort-AV: E=Sophos;i="5.93,337,1654585200"; d="scan'208";a="682328889" Received: from sponnura-mobl1.amr.corp.intel.com (HELO [10.209.58.200]) ([10.209.58.200]) by fmsmga008-auth.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 22 Sep 2022 11:17:53 -0700 Message-ID: <9d3d3424-a6d4-4076-87ff-a1c216de79c6@intel.com> Date: Thu, 22 Sep 2022 11:17:53 -0700 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:91.0) Gecko/20100101 Thunderbird/91.11.0 Subject: Re: [PATCH] ACPI: processor_idle: Skip dummy wait for processors based on the Zen microarchitecture Content-Language: en-US To: "Limonciello, Mario" , "Nayak, K Prateek" , "linux-kernel@vger.kernel.org" Cc: "rafael@kernel.org" , "lenb@kernel.org" , "linux-acpi@vger.kernel.org" , "linux-pm@vger.kernel.org" , "dave.hansen@linux.intel.com" , "bp@alien8.de" , "tglx@linutronix.de" , "andi@lisas.de" , "puwen@hygon.cn" , "peterz@infradead.org" , "rui.zhang@intel.com" , "gpiccoli@igalia.com" , "daniel.lezcano@linaro.org" , "Narayan, Ananth" , "Shenoy, Gautham Ranjal" , "Ong, Calvin" , "stable@vger.kernel.org" , "regressions@lists.linux.dev" References: <20220921063638.2489-1-kprateek.nayak@amd.com> <20e78a49-25df-c83d-842e-1d624655cfd7@intel.com> <0885eecb-042f-3b74-2965-7d657de59953@amd.com> <88c17568-8694-940a-0f1f-9d345e8dcbdb@intel.com> From: Dave Hansen In-Reply-To: Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-pm@vger.kernel.org On 9/22/22 10:48, Limonciello, Mario wrote: > > 2) The title says to limit it to old intel systems, but nothing about this actually enforces that. > It actually is limited to all Intel systems, but effectively won't be used on anything but new > ones because of intel_idle. > > As an idea for #2 you could check for CONFIG_INTEL_IDLE in the Intel case and > if it's not defined show a pr_notice_once() type of message trying to tell people to use > Intel Idle instead for better performance. What does that have to do with *this* patch, though? If you've got CONFIG_INTEL_IDLE disabled, you'll be slow before this patch. You'll also be slow after this patch. It's entirely orthogonal. I can add a "Practically" to the subject so folks don't confuse it with some hard limit that is being enforced: ACPI: processor idle: Practically limit "Dummy wait" workaround to old Intel systems BTW, is there seriously a strong technical reason that AMD systems are still using this code? Or is it pure inertia?