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=-8.3 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE, SPF_PASS,USER_AGENT_SANE_1 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 02892C4363D for ; Tue, 6 Oct 2020 21:18:26 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id AE612206BE for ; Tue, 6 Oct 2020 21:18:25 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727499AbgJFVSY (ORCPT ); Tue, 6 Oct 2020 17:18:24 -0400 Received: from outbound-smtp56.blacknight.com ([46.22.136.240]:34357 "EHLO outbound-smtp56.blacknight.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727365AbgJFVSY (ORCPT ); Tue, 6 Oct 2020 17:18:24 -0400 Received: from mail.blacknight.com (pemlinmail04.blacknight.ie [81.17.254.17]) by outbound-smtp56.blacknight.com (Postfix) with ESMTPS id 560E5FB784 for ; Tue, 6 Oct 2020 22:18:22 +0100 (IST) Received: (qmail 7675 invoked from network); 6 Oct 2020 21:18:22 -0000 Received: from unknown (HELO techsingularity.net) (mgorman@techsingularity.net@[84.203.22.4]) by 81.17.254.9 with ESMTPSA (AES256-SHA encrypted, authenticated); 6 Oct 2020 21:18:22 -0000 Date: Tue, 6 Oct 2020 22:18:20 +0100 From: Mel Gorman To: "Rafael J. Wysocki" Cc: Takashi Iwai , linux-kernel@vger.kernel.org Subject: Re: ACPI _CST introduced performance regresions on Haswll Message-ID: <20201006211820.GN3227@techsingularity.net> References: <20201006083639.GJ3227@techsingularity.net> <20201006190322.GL3227@techsingularity.net> <25f31d3e-7a67-935f-93ba-32216a5084e2@intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-15 Content-Disposition: inline In-Reply-To: <25f31d3e-7a67-935f-93ba-32216a5084e2@intel.com> User-Agent: Mutt/1.10.1 (2018-07-13) Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, Oct 06, 2020 at 09:29:24PM +0200, Rafael J. Wysocki wrote: > > After the commit, the default_status file does not appear in /sys > > > Something is amiss, then, because the commit doesn't affect the presence of > this file. > This was cleared up in another mail. > The only thing it does is to set the use_acpi flag for several processor > models in intel_idle.c. > > It can be effectively reversed by removing all of the ".use_acpi = true," > lines from intel_idle.c. > > In particular, please check if changing the value of use_acpi in struct > idle_cpu_hsx from 'true' to 'false' alone (without reverting the commit) > makes the issue go away in 5.9-rc8 (the default_status file should be > present regardless). > Thanks. I applied the following diff --git a/drivers/idle/intel_idle.c b/drivers/idle/intel_idle.c index 9a810e4a7946..6478347669a9 100644 --- a/drivers/idle/intel_idle.c +++ b/drivers/idle/intel_idle.c @@ -1044,7 +1044,7 @@ static const struct idle_cpu idle_cpu_hsw __initconst = { static const struct idle_cpu idle_cpu_hsx __initconst = { .state_table = hsw_cstates, .disable_promotion_to_c1e = true, - .use_acpi = true, + .use_acpi = false, }; netperf UDP_STREAM pre enable enable 5.9-rc8 5.9-rc8 cst cst cst-no-hsx-acpi vanilla no-hsx-acpi Hmean send-64 203.96 ( 0.00%) 179.23 * -12.13%* 201.04 ( -1.44%) 203.24 ( -0.36%) 233.43 * 14.45%* Hmean send-128 403.66 ( 0.00%) 355.99 * -11.81%* 402.28 ( -0.34%) 387.65 * -3.97%* 461.47 * 14.32%* Hmean send-256 784.39 ( 0.00%) 697.78 * -11.04%* 782.15 ( -0.29%) 758.49 * -3.30%* 895.31 * 14.14%* Hmean recv-64 203.96 ( 0.00%) 179.23 * -12.13%* 201.04 ( -1.44%) 203.24 ( -0.36%) 233.43 * 14.45%* Hmean recv-128 403.66 ( 0.00%) 355.99 * -11.81%* 402.28 ( -0.34%) 387.65 * -3.97%* 461.47 * 14.32%* Hmean recv-256 784.39 ( 0.00%) 697.78 * -11.04%* 782.15 ( -0.29%) 758.49 * -3.30%* 895.28 * 14.14%* This is a more limited run to save time but is enough to illustrate the point. pre-cst is just before your patch enable-cst is your patch that was bisected enable-cst-no-hsx-acpi is your patch with use_acpi disabled 5.9-rc8-vanilla is what it sounds like 5.9-rc8-no-hsx-acpi disables use_acpi The enable-cst-no-hsx-acpi result indicates that use_acpi was the issue for Haswell (at least these machines). Looking just at 5.9-rc8-vanillaa might have been misleading because its performance is not far off the baseline due to unrelated changes that mostly offset the performance penalty. The key question is -- how appropriate would it be to disable acpi for Haswell? Would that be generally safe or could it hide other surprises? -- Mel Gorman SUSE Labs