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=-5.3 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS, USER_AGENT_SANE_1 autolearn=no 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 3F6B9C4363D for ; Fri, 25 Sep 2020 14:17:19 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 0195F20BED for ; Fri, 25 Sep 2020 14:17:18 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728854AbgIYORR (ORCPT ); Fri, 25 Sep 2020 10:17:17 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:51802 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727733AbgIYORP (ORCPT ); Fri, 25 Sep 2020 10:17:15 -0400 Received: from tartarus.angband.pl (tartarus.angband.pl [IPv6:2001:41d0:602:dbe::8]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 38F6DC0613CE for ; Fri, 25 Sep 2020 07:17:15 -0700 (PDT) Received: from kilobyte by tartarus.angband.pl with local (Exim 4.92) (envelope-from ) id 1kLoWv-00037A-Bg; Fri, 25 Sep 2020 16:16:57 +0200 Date: Fri, 25 Sep 2020 16:16:57 +0200 From: Adam Borowski To: Greg KH Cc: Thomas Gleixner , Prasad Sodagudi , rostedt@goodmis.org, pmladek@suse.com, sergey.senozhatsky@gmail.com, linux-kernel@vger.kernel.org, tkjos@google.com, Mohammed Khajapasha Subject: Re: [PATCH 2/2] printk: Make the console flush configurable in hotplug path Message-ID: <20200925141657.GA6325@angband.pl> References: <1600906112-126722-1-git-send-email-psodagud@codeaurora.org> <1600906112-126722-2-git-send-email-psodagud@codeaurora.org> <20200924063352.GB592892@kroah.com> <87wo0j6nos.fsf@nanos.tec.linutronix.de> <20200925092754.GA2508526@kroah.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <20200925092754.GA2508526@kroah.com> X-Junkbait: aaron@angband.pl, zzyx@angband.pl User-Agent: Mutt/1.10.1 (2018-07-13) X-SA-Exim-Connect-IP: X-SA-Exim-Mail-From: kilobyte@angband.pl X-SA-Exim-Scanned: No (on tartarus.angband.pl); SAEximRunCond expanded to false Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, Sep 25, 2020 at 11:27:54AM +0200, Greg KH wrote: > On Thu, Sep 24, 2020 at 08:21:07PM +0200, Thomas Gleixner wrote: > > On Thu, Sep 24 2020 at 08:33, Greg KH wrote: > > > On Wed, Sep 23, 2020 at 05:08:32PM -0700, Prasad Sodagudi wrote: > > >> +config CONSOLE_FLUSH_ON_HOTPLUG > > >> + bool "Enable console flush configurable in hot plug code path" > > CPU hotplug is not meant to be a high speed operation and if people > > think they need it to be fast then its pretty much guaranteed that they > > want it for the completely wrong reasons. > > Odds are, it's the big/little systems that are trying to use cpu hotplug > for this type of thing :( Just a bit of info: My MT6797X (10 core: 4×A53 + 4×A53 + 2×A72), flickers its cores this way: the right-hand piece is CPUs, one character per core: bars show utilization, "o" stands for offline; every line is 0.1 second interval. topline -i 0.1 mmcblk(⠀) (oooo▄▆oo▅o) mmcblk(⠀) (oooo▅▄oooo) mmcblk(⠀) (oooo▆▆oooo) mmcblk(⠀) (oooo▅ooo▆o) mmcblk(⠀) (oooo▆▆oo▄o) mmcblk(⠀) (oooo▆▇oooo) mmcblk(⠀) (oooo▇ooo▅o) mmcblk(⠀) (oooo▆ooo█o) mmcblk(⠀) (oooo▆ooo▄o) mmcblk(⠀) (oooo▅ooo▆o) mmcblk(⠀) (oooo▆ooo▅o) mmcblk(⠀) (oooo▄ooo▇o) mmcblk(⠀) (oooo▇▆oo▆o) mmcblk(⠀) (oooo▆ooo▅o) mmcblk(⠀) (oooo▅▆oooo) mmcblk(⠀) (oooo▆█oooo) mmcblk(⠀) (oooo▆▇oooo) mmcblk(⠀) (oooo▆▆oooo) mmcblk(⠀) (oooo▅▆oooo) mmcblk(⠀) (oooo▆▅oooo) mmcblk(⠀) (oooo▆ooo▆o) mmcblk(⠀) (oooo▆ooo▇o) mmcblk(⢀) (oooo▆▇oo▆o) mmcblk(⠀) (oooo▄ooo▆o) mmcblk(⠀) (oooo▆ooo█o) mmcblk(⠀) (oooo▄ooo▇o) mmcblk(⠀) (oooo▄▆oooo) mmcblk(⠀) (oooo▆▆oooo) So it's on the order of a few ons/offs per second. The offline CPUs are "present" and "offline"; not sure if this means hotplug or not (I'd expect dropping from "present" to "possible", but I don't know these parts). Meow! -- ⢀⣴⠾⠻⢶⣦⠀ ⣾⠁⢠⠒⠀⣿⡁ in the beginning was the boot and root floppies and they were good. ⢿⡄⠘⠷⠚⠋⠀ -- on #linux-sunxi ⠈⠳⣄⠀⠀⠀⠀