From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Cyrus-Session-Id: sloti22d1t05-3648885-1522569955-2-928872815967038407 X-Sieve: CMU Sieve 3.0 X-Spam-known-sender: no X-Spam-score: 0.0 X-Spam-hits: BAYES_00 -1.9, HEADER_FROM_DIFFERENT_DOMAINS 0.249, ME_NOAUTH 0.01, RCVD_IN_DNSWL_HI -5, T_RP_MATCHES_RCVD -0.01, LANGUAGES en, BAYES_USED global, SA_VERSION 3.4.0 X-Spam-source: IP='209.132.180.67', Host='vger.kernel.org', Country='CN', FromHeader='org', MailFrom='org' X-Spam-charsets: plain='us-ascii' X-Resolved-to: greg@kroah.com X-Delivered-to: greg@kroah.com X-Mail-from: linux-serial-owner@vger.kernel.org ARC-Seal: i=1; a=rsa-sha256; cv=none; d=messagingengine.com; s=fm2; t= 1522569955; b=gMeM4XQFjtxgiwCQAUKlDzCbSmmQDZswOOsu3hEpIJVULBpzFf 4X76I4wMxWohWTl05dwDRaEtOLJ7BaLYY610lP5gYLc8+hRphJ2Z2EiLWrodiEX3 8zyzRHbomltMOYQ0ITxxClhWkU+f5xWbjbQZYzNE33h5NznytY2tTf5efw4UEKep HCsC4PiOCtu3z/haUKTpGgluHfk9Ya8Oy7tU1ef1Omp6gCMwhJXpXOGQ+VbZF946 tZdh2JIUukjPbCirS+ZeKiQ0Q//3gi0+PivsrO5bXTYDkxSGDt9dt4PkbOwPSHTU l1QLyMViWAlKCVhdQRHRIXnFfpVmrFHX7/Rw== ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d= messagingengine.com; h=date:from:to:cc:subject:message-id :references:mime-version:content-type:in-reply-to:sender :list-id; s=fm2; t=1522569955; bh=Jd43sewebDaTfzSRS/tnedwiXwBOSt nOoAPlZHoOOWY=; b=Z2w1uc7JB93ycPneqBruRYMSNNH5HwrvJvVAATDgM+9kgX ozTjZM5kFzE+38IuULPblLxoszpD7agTxU6kZcIPT4N1nfwPIcQA2eXdCmto+WyZ qyC4TdsY4K5/G8OdcWHSU1oUU7yfdrBv4p4RdrccEokQkUKT+fNGcd+8xKX6fxqI YcLsM2SvPq6jnCYwaLBstpCz/zWbBW2jXryp482nB4+AgZ+xKkJHHy6nsiE7lGNn lALBqvw3LHWwUfCb8+Z7TL96sDtKA+VLbW5ugSJDEc+DteN9rmqAsCg80A16RPS4 4hMq5IplCbmVcAF/uSBHeiNp8nPaA8zQsvpU+bBQ== ARC-Authentication-Results: i=1; mx5.messagingengine.com; arc=none (no signatures found); dkim=none (no signatures found); dmarc=none (p=none,has-list-id=yes,d=none) header.from=linuxfoundation.org; iprev=pass policy.iprev=209.132.180.67 (vger.kernel.org); spf=none smtp.mailfrom=linux-serial-owner@vger.kernel.org smtp.helo=vger.kernel.org; x-aligned-from=fail; x-cm=none score=0; x-ptr=pass x-ptr-helo=vger.kernel.org x-ptr-lookup=vger.kernel.org; x-return-mx=pass smtp.domain=vger.kernel.org smtp.result=pass smtp_org.domain=kernel.org smtp_org.result=pass smtp_is_org_domain=no header.domain=linuxfoundation.org header.result=pass header_is_org_domain=yes; x-vs=clean score=0 state=0 Authentication-Results: mx5.messagingengine.com; arc=none (no signatures found); dkim=none (no signatures found); dmarc=none (p=none,has-list-id=yes,d=none) header.from=linuxfoundation.org; iprev=pass policy.iprev=209.132.180.67 (vger.kernel.org); spf=none smtp.mailfrom=linux-serial-owner@vger.kernel.org smtp.helo=vger.kernel.org; x-aligned-from=fail; x-cm=none score=0; x-ptr=pass x-ptr-helo=vger.kernel.org x-ptr-lookup=vger.kernel.org; x-return-mx=pass smtp.domain=vger.kernel.org smtp.result=pass smtp_org.domain=kernel.org smtp_org.result=pass smtp_is_org_domain=no header.domain=linuxfoundation.org header.result=pass header_is_org_domain=yes; x-vs=clean score=0 state=0 X-ME-VSCategory: clean X-CM-Envelope: MS4wfG5NJoApsPsU8Wx07phiZHzAiYR9JRsoc+cWOXNuRzxT78CV1gpFHeqfGYo7JUIFPw9wNECi8spjrRQOOpDLJamrui4n6GWc27J0i2W+7tCISDZYWGyi b+BSwgdG1zQibUDoSOanD7EGzmaK7IXi3szWCB5DS4kwGazncZYddpghBcEJXkGDQAeZPt0SMTR6SY65JW4wTOdFV7t/f/tHykGY6ispjkRpUwEMBpBnXZ6d X-CM-Analysis: v=2.3 cv=NPP7BXyg c=1 sm=1 tr=0 a=UK1r566ZdBxH71SXbqIOeA==:117 a=UK1r566ZdBxH71SXbqIOeA==:17 a=kj9zAlcOel0A:10 a=Kd1tUaAdevIA:10 a=VwQbUJbxAAAA:8 a=J3XSWAmw1PxaEGvPMoQA:9 a=CjuIK1q_8ugA:10 a=x8gzFH9gYPwA:10 a=AjGcO6oz07-iQ99wixmX:22 X-ME-CMScore: 0 X-ME-CMCategory: none Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751386AbeDAIFw (ORCPT ); Sun, 1 Apr 2018 04:05:52 -0400 Received: from mail.linuxfoundation.org ([140.211.169.12]:51986 "EHLO mail.linuxfoundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751381AbeDAIFv (ORCPT ); Sun, 1 Apr 2018 04:05:51 -0400 Date: Sun, 1 Apr 2018 10:05:46 +0200 From: Greg Kroah-Hartman To: Paul Menzel Cc: linux-serial@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: How to move serial8250_init out of the critical path to decrease boot time? Message-ID: <20180401080546.GA31356@kroah.com> References: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.9.4 (2018-02-28) Sender: linux-serial-owner@vger.kernel.org X-Mailing-List: linux-serial@vger.kernel.org X-getmail-retrieved-from-mailbox: INBOX X-Mailing-List: linux-kernel@vger.kernel.org List-ID: On Sun, Apr 01, 2018 at 09:11:15AM +0200, Paul Menzel wrote: > Dear Linux folks, > > > The goal is to boot a *distribution* Linux kernel as fast as possible. (The > goal is currently 500 ms.) What distro? > With Linux 4.16-rc7, `serial8250_init()` takes almost 34 ms according to > `initcall_debug` on the laptop TUXEDO Book BU1406 with an Intel Kaby Lake > processor. > > ``` > [ 2.657950] calling serial8250_init+0x0/0x168 @ 1 > [ 2.657963] Serial: 8250/16550 driver, 32 ports, IRQ sharing enabled > [ 2.692598] initcall serial8250_init+0x0/0x168 returned 0 after 33820 > usecs > ``` > > One problem is, that the distributions do not build this as a module, > despite more and more devices do not actually have serial connectors, but > the chipset still exposes them. Then fix that in the distro kernel build. > What options are there? File a bug with the distro. > 1. Try to probe it asynchronously as in the attached patch, which is not > tested yet. Please test it and watch to see what breaks :) good luck! greg k-h