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=1.0 required=3.0 tests=DKIM_INVALID,DKIM_SIGNED, FSL_HELO_FAKE,MAILING_LIST_MULTI,SPF_PASS,USER_AGENT_MUTT 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 157E8C64EAD for ; Tue, 9 Oct 2018 06:13:07 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 97B77213A2 for ; Tue, 9 Oct 2018 06:13:06 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=fail reason="signature verification failed" (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b="ZpBj9+LR" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 97B77213A2 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=kernel.org 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 S1726582AbeJIN14 (ORCPT ); Tue, 9 Oct 2018 09:27:56 -0400 Received: from mail-wr1-f41.google.com ([209.85.221.41]:39244 "EHLO mail-wr1-f41.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726451AbeJIN14 (ORCPT ); Tue, 9 Oct 2018 09:27:56 -0400 Received: by mail-wr1-f41.google.com with SMTP id 61-v6so392496wrb.6 for ; Mon, 08 Oct 2018 23:12:38 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=sender:date:from:to:cc:subject:message-id:references:mime-version :content-disposition:in-reply-to:user-agent; bh=8bdlqv+fk+B9p2/xRp1EpZH62eATHLa+d39zf0LLb1c=; b=ZpBj9+LRib1+bJvhep7VRjHopB0dUksl7EqS7aakIpnQn8Ex8GY5Ul1NgJ4Rl6+uPc M60ZudX+AVmtECWNl6YvoPBLOP8jQ8dLmc3mOGuRiLkeCa09Ck683pjqiiUfw2dRvq0V 6OEYP0c7TLU4N47voTO4NpM1onyWIFbBzyVMqOvXHJ6Rduyq3GNhi8NrwF7O+86jqHGc lBGSvOdssusXxesjA4RQVa2eOurB57Z075clQj89JHfxe/Yc+TPpUUf5XUO4Ssr8D5ks qKNyiKrj8c6rXk2Op2cMyli49yFyByu/9nk7wN4h9ATPC38/2zgcv40r4AW0494NA3v9 2/PA== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:sender:date:from:to:cc:subject:message-id :references:mime-version:content-disposition:in-reply-to:user-agent; bh=8bdlqv+fk+B9p2/xRp1EpZH62eATHLa+d39zf0LLb1c=; b=FUAZda0YJ0xMByT9Pi174CV4A93yCG5GF5692kjH+pq0dUWFZIjIfD6I9nElGwbpBN 1ieNFs7gLeKQzIwAXDLkz0ElhygwZWTUH56N1HzN5k81kOpyYfOL3kiTvYlQ2VRC8vX4 4JYEOiFa4XdcZHJyDoR2fA97658M5GaRd97gYrDSA9tzfMSpMlipihXpwl1lZFAh73BU GD5Ani3Mvy1+Wb+j5EbV+BVzTVLHd6REEs8Wsp7GqN8d6Ecu8J9zkpMmHq1KntnJMgJI 59l9ZCATAWzqqiNmp6FHJ1/B8ZOU5SZ+BkVSDIRRlq1wLrYvZpvAW3u2qQnKVtjCuX6i qTlw== X-Gm-Message-State: ABuFfogaXlCUXcU9sS+57kKZyt44I3jNqIfvE/ictmGvbg6O/vgbVm8n hdNmB+/IkpzCCKjmuhl+UgU= X-Google-Smtp-Source: ACcGV634Ikc7QnZG8w8h/Rdo/NdUlHDaXBaH4PBlDhSN1Yhdx9gPaB+tN3qv2FYwk22vb2ISCK0rcw== X-Received: by 2002:adf:b109:: with SMTP id l9-v6mr18090761wra.101.1539065557699; Mon, 08 Oct 2018 23:12:37 -0700 (PDT) Received: from gmail.com (2E8B0CD5.catv.pool.telekom.hu. [46.139.12.213]) by smtp.gmail.com with ESMTPSA id 90-v6sm24217542wrg.86.2018.10.08.23.12.36 (version=TLS1_2 cipher=ECDHE-RSA-CHACHA20-POLY1305 bits=256/256); Mon, 08 Oct 2018 23:12:36 -0700 (PDT) Date: Tue, 9 Oct 2018 08:12:34 +0200 From: Ingo Molnar To: Josh Poimboeuf Cc: Paul Menzel , Thomas Gleixner , Ingo Molnar , Borislav Petkov , x86@kernel.org, LKML Subject: Re: unwind_init() takes 100 ms Message-ID: <20181009061234.GA116930@gmail.com> References: <81a1ff79-b303-c384-f926-c9618afac8f0@molgen.mpg.de> <20181008173417.crlfndi3p5pevnx3@treble> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20181008173417.crlfndi3p5pevnx3@treble> User-Agent: Mutt/1.9.4 (2018-02-28) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org * 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. I don't agree with such a kludge: 100 msecs isn't the end of the world for a distro kernel bootup which takes a lot longer than that typically, and we'd like to see the build time sorting implemented as well. Let's fix this for real intstead of a workaround that is going to decrease the debuggability of the kernel *significantly*. > I'm not sure about a runtime toggle though. It might be racy and I'd > rather avoid that completely, unless there's a solid justification for > it. No, just no ... Debug facilities need to be robust, dependable and as simple as possible. Thanks, Ingo