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 EDF2BCDB47E for ; Fri, 20 Oct 2023 06:18:58 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229735AbjJTGS6 (ORCPT ); Fri, 20 Oct 2023 02:18:58 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:56044 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229558AbjJTGS6 (ORCPT ); Fri, 20 Oct 2023 02:18:58 -0400 Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id D17AED49 for ; Thu, 19 Oct 2023 23:18:56 -0700 (PDT) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 0D1F1C433C8; Fri, 20 Oct 2023 06:18:55 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1697782736; bh=XGhXOEjRhO0Vw5HK9APyCr6eHZI1/Lb/6opavS/zxGU=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=xyTCiVng2inuuKGOitO+jgJSfzL4bxlyem7nrYvK9PG9Vpn58CMFTR+NV/k23qSf6 QzGK0QNBKP3ngL5Ri9mANWS7yULBZD3nFQVSbuUzQM5h/kynUGMq2vmMFJxC1D3QTh ztu7RnE9PWijI79M4PDtDkn1vcVIp4ENG6rYX2G0= Date: Fri, 20 Oct 2023 08:11:36 +0200 From: Greg KH To: Hyeonggon Yoo <42.hyeyoo@gmail.com> Cc: Luiz Capitulino , "stable@vger.kernel.org" , "sashal@kernel.org" Subject: Re: [6.1] Please apply cc6003916ed46d7a67d91ee32de0f9138047d55f Message-ID: <2023102026-zookeeper-retreat-b38f@gregkh> References: <97397e8d-f447-4cf7-84a1-070989d0a7fd@amazon.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: Precedence: bulk List-ID: X-Mailing-List: stable@vger.kernel.org On Fri, Oct 20, 2023 at 11:46:36AM +0900, Hyeonggon Yoo wrote: > On Fri, Oct 20, 2023 at 10:27 AM Luiz Capitulino wrote: > > > > Hi, > > > > As reported before[1], we found another regression in 6.1 when doing > > performance comparisons with 5.10. This one is caused by CONFIG_DEBUG_PREEMPT > > being enabled by default by the following upstream commit if you have the > > right config dependencies enabled (commit is introduced in v5.16-rc1): > > > > """ > > commit c597bfddc9e9e8a63817252b67c3ca0e544ace26 > > Author: Frederic Weisbecker > > Date: Tue Sep 14 12:31:34 2021 +0200 > > > > sched: Provide Kconfig support for default dynamic preempt mode > > """ > > > > We found up to 8% performance improvement with CONFIG_DEBUG_PREEMPT > > disabled in different perf benchmarks (including UnixBench process > > creation and redis). The root cause is explained in the commit log > > below which is merged in 6.3 and applies (almost) clealy on 6.1.59. > > Oh, I should've sent it to the stable. Thanks for sending it! > > Yes, DEBUG_PREEMPT was unintentionally enabled after the introduction > of PREEMPT_DYNAMIC. It was already enabled by default for PREEMPTION=y kernels > but PREEMPT_DYNAMIC always enables PREEMPT_BUILD (and hence PREEMPTION) > so distros that were using PREEMPT_VOLUNTARY are silently affected by that. > > It looks appropriate to be backported to the stable tree (to me). > Hmm but I think it should be backported to 5.15 too? Now queued up, thanks. greg k-h