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=-3.0 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 A6C98C04EB9 for ; Mon, 3 Dec 2018 15:06:08 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 73B8720851 for ; Mon, 3 Dec 2018 15:06:08 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 73B8720851 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=suse.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 S1726653AbeLCPGK (ORCPT ); Mon, 3 Dec 2018 10:06:10 -0500 Received: from mx2.suse.de ([195.135.220.15]:37110 "EHLO mx1.suse.de" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1726162AbeLCPGK (ORCPT ); Mon, 3 Dec 2018 10:06:10 -0500 X-Virus-Scanned: by amavisd-new at test-mx.suse.de Received: from relay1.suse.de (unknown [195.135.220.254]) by mx1.suse.de (Postfix) with ESMTP id 3119CAD47; Mon, 3 Dec 2018 15:06:04 +0000 (UTC) Date: Mon, 3 Dec 2018 16:06:03 +0100 From: Petr Mladek To: Tetsuo Handa Cc: Dmitry Vyukov , Sergey Senozhatsky , Sergey Senozhatsky , Steven Rostedt , Linus Torvalds , Andrew Morton , LKML Subject: Re: [PATCH] printk: Add caller information to printk() output. Message-ID: <20181203150603.cdqii263e4kmmibo@pathway.suse.cz> References: <1543045075-3008-1-git-send-email-penguin-kernel@I-love.SAKURA.ne.jp> <20181130154024.ls3mntfdr4zvluub@pathway.suse.cz> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: NeoMutt/20170421 (1.8.2) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Sat 2018-12-01 23:44:37, Tetsuo Handa wrote: > On 2018/12/01 0:40, Petr Mladek wrote: > >> Some examples for console output: > >> > >> [ 0.293000] [T1] smpboot: CPU0: Intel(R) Core(TM) i5-4440S CPU @ 2.80GHz (family: 0x6, model: 0x3c, stepping: 0x3) > >> [ 0.299733] [T1] Performance Events: Haswell events, core PMU driver. > >> [ 2.813808] [T35] clocksource: Switched to clocksource tsc > >> [ 2.893984] [C0] random: fast init done > > ^ > > > > Please, remove the space between the timestamp and the from field. > > This space was emitted by print_time(). Do we want to modify print_time() > not to emit this space if the from field is printed? Exactly. This is what I thought about. > If we modify print_time(), I think that the leading spaces inserted by "%5lu" > makes little sense, for "%5lu" is too small for systems with uptime >= 1.16 days > and parsers after all cannot assume fixed length for the timestamp field. Then, > we could change from "%5lu.%06lu" to "%lu.%06lu" so that parsers (like /bin/awk) > can get prefix part using white spaces as a delimiter. My primary concern was a human readability. The different header columns are separated by brackets and the message itself is separated by the space. awk could easily use \[ as the separator. But you made a good point about the column width. The text might be hard to read when every line of text starts on a different column. And the might be bigger differences for the task id. It might be useful to add some reasonable default width also for the for the "from_id" column. > If we want to reduce space, do we want to do like > > [0.293000@T1] smpboot: CPU0: Intel(R) Core(TM) i5-4440S CPU @ 2.80GHz (family: 0x6, model: 0x3c, stepping: 0x3) > [0.299733@T1] Performance Events: Haswell events, core PMU driver. > [2.813808@T35] clocksource: Switched to clocksource tsc > [2.893984@C0] random: fast init done Hmm, this is pretty hard to parse by my eyes. Also it changes the format of the timestamp column. I think that the following might give the best human user experience: [ 0.293000][ T1] smpboot: CPU0: Intel(R) Core(TM) i5-4440S CPU @ 2.80GHz (family: 0x6, model: 0x3c, stepping: 0x3) [ 0.299733][ T1] Performance Events: Haswell events, core PMU driver. [ 2.813808][ T35] clocksource: Switched to clocksource tsc [ 2.893984][ C0] random: fast init done > >> @@ -1037,6 +1054,9 @@ void log_buf_vmcoreinfo_setup(void) > >> VMCOREINFO_OFFSET(printk_log, len); > >> VMCOREINFO_OFFSET(printk_log, text_len); > >> VMCOREINFO_OFFSET(printk_log, dict_len); > >> +#ifdef CONFIG_PRINTK_FROM > >> + VMCOREINFO_OFFSET(printk_log, from_id); > >> +#endif > > > > The crash tool would need to be updated if anyone wanted to read > > the log from the extended structure. Well, it might be done later > > if people start using it more widely. > > Since syzbot can utilize output from only normal consoles, I can > keep extended records unmodified for now. Please, add VMCOREINFO_OFFSET(printk_log, from_id) so that crashdump can be updated when necessary. > > > > I think about adding one more filed "u8 version". It would help > > to solve the external compatibility in the long term. > > /dev/kmsg format allows adding more fields, but that format did not define > how to tell what fields are there. If fields are conditionally added by > kernel config options, I don't think that "u8 version" field helps. > Unless we add fields unconditionally, we will need to use $name=$value > (where $name and $value must not contain ',' and ';') representation. /dev/kmsg uses key=value notation. It does not need any version. The version filed was intended for crashdump. It would make the life easier for its maintainers. Well, I do not resist on it. Let's put the version field aside for now. Best Regards, Petr