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 406E8C433F5 for ; Fri, 11 Mar 2022 11:38:09 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1348091AbiCKLjK (ORCPT ); Fri, 11 Mar 2022 06:39:10 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:38434 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S232676AbiCKLjH (ORCPT ); Fri, 11 Mar 2022 06:39:07 -0500 Received: from ams.source.kernel.org (ams.source.kernel.org [IPv6:2604:1380:4601:e00::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id D7AD863507 for ; Fri, 11 Mar 2022 03:38:03 -0800 (PST) Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by ams.source.kernel.org (Postfix) with ESMTPS id 954D1B82AD2 for ; Fri, 11 Mar 2022 11:38:02 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 1A09EC340E9; Fri, 11 Mar 2022 11:37:57 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1646998681; bh=e4y3Z0M6OHH8hOOsfv+op+DHBVtoqM4faCpqS9Xl8uU=; h=Subject:From:To:Cc:Date:In-Reply-To:References:From; b=g1jxaks/+lJoF0nO1IAAjxawKI0ko+aKkwulHRxCgZnr1xWbUVBLR7c1jdMN+w+U2 6cm+tTiVqaowR5Ncg4U1esB4Ey5SXwONGFW4fAyQSvddk4B6dQavU1v/gyitXcUMtN FylD1vi4UaqJbo4yeGSTinuYHvS5j2ZNSYtUOBMDqDI5+hVyF84mx5PHq1jObzbLnl O+jWJhUavz3LM9nWyTvQQcu0LzzJL5FBguiegnqP8+Omnc6wusNY7v9dY8sJOUzCI4 EMePzLFBq+97ctuNIUOvMpIs2kr1KkhiehRXV+TE2ewdpmNK6q+4zhB2UDXSlRu0uz ORzwPjb75UpNg== Message-ID: Subject: Re: [PATCH 00/19] rcu/context-tracking: Merge RCU eqs-dynticks counter to context tracking From: nicolas saenz julienne To: Frederic Weisbecker , LKML Cc: Peter Zijlstra , Phil Auld , Alex Belits , Xiongfeng Wang , Neeraj Upadhyay , Thomas Gleixner , Yu Liao , Boqun Feng , "Paul E . McKenney" , Marcelo Tosatti , Paul Gortmaker , Uladzislau Rezki , Joel Fernandes Date: Fri, 11 Mar 2022 12:37:55 +0100 In-Reply-To: <20220302154810.42308-1-frederic@kernel.org> References: <20220302154810.42308-1-frederic@kernel.org> Content-Type: text/plain; charset="UTF-8" User-Agent: Evolution 3.42.4 (3.42.4-1.fc35) MIME-Version: 1.0 Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, 2022-03-02 at 16:47 +0100, Frederic Weisbecker wrote: > This mixes up the RCU dynticks counter and the context tracking state > updates into a single atomic instruction. This may serve several > purposes: > > 1) Improve CPU isolation with deferring some disturbances until sensitive > userspace workload completes and goes to the kernel. This can take > several forms, for example smp_call_function_housekeeping() or > on_each_housekeeping_cpu() to enqueue and execute work on all > housekeeping CPUs. Then an atomic operation on ct->state can defer > the work on nohz_full CPUs until they run in kernel (or IPI them > if they are in kernel mode), see this proposal by Peter: > https://lore.kernel.org/all/20210929151723.162004989@infradead.org/#r > > 2) Unearth sysidle (https://git.kernel.org/pub/scm/linux/kernel/git/paulmck/linux-rcu.git/commit/?h=sysidle.2017.05.11a&id=fe5ac724d81a3c7803e60c2232718f212f3f38d4) > This feature allowed to shutdown the tick on the last housekeeping > CPU once the rest of the system is fully idle. We needed some proper > fully ordered context tracking for that. > > Inspired by Peterz: https://lore.kernel.org/all/20210929151723.162004989@infradead.org > > git://git.kernel.org/pub/scm/linux/kernel/git/frederic/linux-dynticks.git > rcu/context-tracking > > HEAD: e4eaff86ec91c1cbde9a113cf5232dac9f897337 > > Thanks, > Frederic > --- I've been testing patches 1 to 18 on my nohz_full setup. Everything is looking good so far. Regards, Nicolas