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, URIBL_BLOCKED,USER_AGENT_SANE_2 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 5B5B9C47425 for ; Thu, 24 Sep 2020 14:58:35 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 1AC4E2395C for ; Thu, 24 Sep 2020 14:58:34 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728401AbgIXO6d (ORCPT ); Thu, 24 Sep 2020 10:58:33 -0400 Received: from mail.kernel.org ([198.145.29.99]:37456 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728385AbgIXO62 (ORCPT ); Thu, 24 Sep 2020 10:58:28 -0400 Received: from oasis.local.home (cpe-66-24-58-225.stny.res.rr.com [66.24.58.225]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id 1FDEF2396D; Thu, 24 Sep 2020 14:58:26 +0000 (UTC) Date: Thu, 24 Sep 2020 10:58:23 -0400 From: Steven Rostedt To: peterz@infradead.org Cc: Prasad Sodagudi , tglx@linutronix.de, qais.yousef@arm.com, mingo@kernel.org, cai@lca.pw, tyhicks@canonical.com, arnd@arndb.de, rameezmustafa@codeaurora.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH 0/2] measure latency of cpu hotplug path Message-ID: <20200924105823.0e11f2e4@oasis.local.home> In-Reply-To: <20200924083414.GB1362448@hirez.programming.kicks-ass.net> References: <1600904266-102397-1-git-send-email-psodagud@codeaurora.org> <20200924083414.GB1362448@hirez.programming.kicks-ass.net> X-Mailer: Claws Mail 3.17.3 (GTK+ 2.24.32; x86_64-pc-linux-gnu) MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, 24 Sep 2020 10:34:14 +0200 peterz@infradead.org wrote: > On Wed, Sep 23, 2020 at 04:37:44PM -0700, Prasad Sodagudi wrote: > > There are all changes related to cpu hotplug path and would like to seek > > upstream review. These are all patches in Qualcomm downstream kernel > > for a quite long time. First patch sets the rt prioity to hotplug > > task and second patch adds cpuhp trace events. > > > > 1) cpu-hotplug: Always use real time scheduling when hotplugging a CPU > > 2) cpu/hotplug: Add cpuhp_latency trace event > > Why? Hotplug is a known super slow path. If you care about hotplug > latency you're doing it wrong. I'd like to know the answer to Peter's question too. Why? -- Steve