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=-5.8 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI, SPF_HELO_NONE,SPF_PASS 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 2D432C432BE for ; Wed, 11 Aug 2021 12:27:16 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 106A760FA0 for ; Wed, 11 Aug 2021 12:27:16 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S238859AbhHKM1i (ORCPT ); Wed, 11 Aug 2021 08:27:38 -0400 Received: from Galois.linutronix.de ([193.142.43.55]:51266 "EHLO galois.linutronix.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S238566AbhHKMZx (ORCPT ); Wed, 11 Aug 2021 08:25:53 -0400 From: Thomas Gleixner DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020; t=1628684729; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=9Fc7r61LCYAdoePXBxI4aA4CJKIy5jDNHM9L9gFB7dA=; b=eaojQdyePYuh2fjOmp9v44XjAja9d7cU7a75zQuTnBs2d6ob7dCsUfp9YB8VTHa/vWg+rg HmUggl9EU+mAeq0VamEjZn7Gbcisrw7QAgyMr0tOLCi0mbCkjD+lEYI+A/a9WPR8MVBVY7 KWh0kytOv2SBYwXAHcZlyHQlg+1xFObnSZ7zi2+gw019y+ZLwLZGLBA2LbuPW3GdSh1Euq L3yMhmJgAZK0xkOkRObihMdjq4D5C6cVbiWqLCQPGbDIXu1gKjprGah/ziCSKMAi02u+Lh K69xQcIIwoTBE44SlhlgjdtJAsy580dqIn4ZSU/dqcoTE/an/msUvSvB5DNwdQ== DKIM-Signature: v=1; a=ed25519-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020e; t=1628684729; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=9Fc7r61LCYAdoePXBxI4aA4CJKIy5jDNHM9L9gFB7dA=; b=GlohVzjUlTTzk5ErNHrzpKzTts7XWdgsp0gkXse0h6oRLUuabxhz7MH6HbAGKawF3mEDlp AcN/28GRBo0+IaBQ== To: Sebastian Andrzej Siewior Cc: Clark Williams , Steven Rostedt , Dmitry Vyukov , Andrey Konovalov , kasan-dev@googlegroups.com, linux-kernel@vger.kernel.org Subject: Re: [PATCH PREEMPT_RT] kcov: fix locking splat from kcov_remote_start() In-Reply-To: <20210811090033.wijh4v37wlnny3ox@linutronix.de> References: <20210809155909.333073de@theseus.lan> <20210810095032.epdhivjifjlmbhp5@linutronix.de> <87sfzhox15.ffs@tglx> <20210811090033.wijh4v37wlnny3ox@linutronix.de> Date: Wed, 11 Aug 2021 14:25:29 +0200 Message-ID: <87czqkp3ra.ffs@tglx> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: quoted-printable Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, Aug 11 2021 at 11:00, Sebastian Andrzej Siewior wrote: > On 2021-08-10 22:38:30 [+0200], Thomas Gleixner wrote: >> And that matters because? kcov has a massive overhead and with that >> enabled you care as much about latencies as you do when running with >> lockdep enabled. > > I wasn't aware of that. However, with that local_irq_save() -> > local_lock_irqsave() swap and that first C code from > Documentation/dev-tools/kcov.rst I don't see any spike in cyclictest's > results. Maybe I'm not using it right=E2=80=A6 The problem starts with remote coverage AFAICT.