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=-2.8 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_PASS,USER_AGENT_NEOMUTT autolearn=ham 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 E0B01C65C20 for ; Mon, 8 Oct 2018 17:36:20 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id B41FF213A2 for ; Mon, 8 Oct 2018 17:36:20 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org B41FF213A2 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=redhat.com Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726721AbeJIAtF (ORCPT ); Mon, 8 Oct 2018 20:49:05 -0400 Received: from mx1.redhat.com ([209.132.183.28]:36220 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726391AbeJIAtE (ORCPT ); Mon, 8 Oct 2018 20:49:04 -0400 Received: from smtp.corp.redhat.com (int-mx03.intmail.prod.int.phx2.redhat.com [10.5.11.13]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id 80C183002E2A; Mon, 8 Oct 2018 17:36:17 +0000 (UTC) Received: from treble (ovpn-121-208.rdu2.redhat.com [10.10.121.208]) by smtp.corp.redhat.com (Postfix) with ESMTPS id AE23967E7A; Mon, 8 Oct 2018 17:36:16 +0000 (UTC) Date: Mon, 8 Oct 2018 12:36:14 -0500 From: Josh Poimboeuf To: Paul Menzel Cc: Thomas Gleixner , Ingo Molnar , Borislav Petkov , x86@kernel.org, LKML Subject: Re: unwind_init() takes 100 ms Message-ID: <20181008173614.bchqq6unw65bc57x@treble> References: <81a1ff79-b303-c384-f926-c9618afac8f0@molgen.mpg.de> <20181008173417.crlfndi3p5pevnx3@treble> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <20181008173417.crlfndi3p5pevnx3@treble> User-Agent: NeoMutt/20180716 X-Scanned-By: MIMEDefang 2.79 on 10.5.11.13 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.43]); Mon, 08 Oct 2018 17:36:17 +0000 (UTC) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, Oct 08, 2018 at 12:34:17PM -0500, Josh Poimboeuf wrote: > > 4. Would a command line parameter be reasonable `disable_unwind`, so people > > could decrease their boot time with distribution kernels, and easily turn it > > back on, when they need a stacktrace without having to rebuild the Linux > > kernel? > > I think a boot cmdline option to disable ORC would be ok. However, > disabling ORC would need to fall back to the "guess" unwinder. > Otherwise it would make debugging impossible. That shouldn't be too > hard, but it would require restructuring the code a bit. But I should also clarify that this option wouldn't be worth it. Sorting at build time is the way to go. -- Josh