From mboxrd@z Thu Jan 1 00:00:00 1970 Return-path: Received: from mx2.suse.de ([195.135.220.15]) by merlin.infradead.org with esmtps (Exim 4.92.3 #3 (Red Hat Linux)) id 1k6ANx-0003Fj-8q for kexec@lists.infradead.org; Thu, 13 Aug 2020 10:23:02 +0000 Date: Thu, 13 Aug 2020 12:22:58 +0200 From: Petr Mladek Subject: Re: [RFC PATCH] printk: Change timestamp to triplet as mono, boot and real Message-ID: <20200813102258.GL12903@alley> References: <1597120822-11999-1-git-send-email-orsonzhai@gmail.com> <20200811094413.GA12903@alley> <87zh7175hj.fsf@nanos.tec.linutronix.de> <20200811130218.GI6215@alley> <20200813015500.GC2020879@jagdpanzerIV.localdomain> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: <20200813015500.GC2020879@jagdpanzerIV.localdomain> List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "kexec" Errors-To: kexec-bounces+dwmw2=infradead.org@lists.infradead.org To: Sergey Senozhatsky Cc: Prarit Bhargava , John Ogness , Orson Zhai , Baoquan He , cixi.geng1@unisoc.com, Stephen Boyd , zhang.lyra@gmail.com, Steven Sistare , kexec@lists.infradead.org, linux-kernel@vger.kernel.org, Steven Rostedt , Jon DeVree , John Stultz , ruifeng.zhang1@unisoc.com, Orson Zhai , Thomas Gleixner , Salvatore Bonaccorso , Dave Young , Dominique Martinet , Vivek Goyal , Pavel Tatashin On Thu 2020-08-13 10:55:00, Sergey Senozhatsky wrote: > On (20/08/11 15:02), Petr Mladek wrote: > > On Tue 2020-08-11 14:05:12, Thomas Gleixner wrote: > > > Petr Mladek writes: > > > > At least "crash" tool would need an update anyway. AFAIK, it checks > > > > the size of struct printk_log and refuses to read it when it changes. > > > > > > > > It means that the hack with VMCOREINFO_FIELD_OFFSET probably is not > > > > needed because we would need to update the crashdump-related tools anyway. > > > > > > > > Well, the timing is good. We are about to switch the printk ring > > > > buffer into a lockless one. It requires updating the crashdump tools > > > > as well. We could do this at the same time. The lockless ring buffer > > > > already is in linux-next. It is aimed for 5.10 or 5.11. > > > ... > > > > It would be great to synchronize all these changes changes of the > > > > printk log buffer structures. > > > > > > I agree that having one update is a good thing, but pretty please can we > > > finally make progress with this and not create yet another dependency? > > > > To make it clear. I definitely do not want to block lockless printk by > > this. > > > > BTW: I am not 100% convinced that storing all three timestamps is > > worth it. It increases the code complexity, metadata size. It needs > > an interface with the userspace that has to stay backward compatible. > > Can we, perhaps, store those various "alternative" timestamps in dict so > then whoever wants to read them can just parse the dict key:value pairs > attach to each printk message? Interesting idea. It might be a way how to add optional metadata without breaking compatibility with crashdump tools. Well, I have bad feeling about it. Some of the reasons might be: + would take more space (prefix + text vs. binary representation) + not reliable because dict is currently dropped when no space + it would make the controversial dictionary feature more important I would prefer to solve this by storing the timestamps in the structure with metadata. Best Regards, Petr _______________________________________________ kexec mailing list kexec@lists.infradead.org http://lists.infradead.org/mailman/listinfo/kexec 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=-5.5 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS, USER_AGENT_SANE_1 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 7EA3FC433DF for ; Thu, 13 Aug 2020 10:23:07 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 63A7020768 for ; Thu, 13 Aug 2020 10:23:07 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726224AbgHMKXF (ORCPT ); Thu, 13 Aug 2020 06:23:05 -0400 Received: from mx2.suse.de ([195.135.220.15]:39220 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726048AbgHMKXB (ORCPT ); Thu, 13 Aug 2020 06:23:01 -0400 X-Virus-Scanned: by amavisd-new at test-mx.suse.de Received: from relay2.suse.de (unknown [195.135.221.27]) by mx2.suse.de (Postfix) with ESMTP id E8798AE16; Thu, 13 Aug 2020 10:23:21 +0000 (UTC) Date: Thu, 13 Aug 2020 12:22:58 +0200 From: Petr Mladek To: Sergey Senozhatsky Cc: Thomas Gleixner , Orson Zhai , Prarit Bhargava , Dave Young , Baoquan He , Vivek Goyal , Steven Rostedt , John Stultz , Stephen Boyd , kexec@lists.infradead.org, linux-kernel@vger.kernel.org, zhang.lyra@gmail.com, ruifeng.zhang1@unisoc.com, cixi.geng1@unisoc.com, Orson Zhai , Pavel Tatashin , Steven Sistare , Dominique Martinet , Jon DeVree , Salvatore Bonaccorso , John Ogness Subject: Re: [RFC PATCH] printk: Change timestamp to triplet as mono, boot and real Message-ID: <20200813102258.GL12903@alley> References: <1597120822-11999-1-git-send-email-orsonzhai@gmail.com> <20200811094413.GA12903@alley> <87zh7175hj.fsf@nanos.tec.linutronix.de> <20200811130218.GI6215@alley> <20200813015500.GC2020879@jagdpanzerIV.localdomain> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20200813015500.GC2020879@jagdpanzerIV.localdomain> User-Agent: Mutt/1.10.1 (2018-07-13) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu 2020-08-13 10:55:00, Sergey Senozhatsky wrote: > On (20/08/11 15:02), Petr Mladek wrote: > > On Tue 2020-08-11 14:05:12, Thomas Gleixner wrote: > > > Petr Mladek writes: > > > > At least "crash" tool would need an update anyway. AFAIK, it checks > > > > the size of struct printk_log and refuses to read it when it changes. > > > > > > > > It means that the hack with VMCOREINFO_FIELD_OFFSET probably is not > > > > needed because we would need to update the crashdump-related tools anyway. > > > > > > > > Well, the timing is good. We are about to switch the printk ring > > > > buffer into a lockless one. It requires updating the crashdump tools > > > > as well. We could do this at the same time. The lockless ring buffer > > > > already is in linux-next. It is aimed for 5.10 or 5.11. > > > ... > > > > It would be great to synchronize all these changes changes of the > > > > printk log buffer structures. > > > > > > I agree that having one update is a good thing, but pretty please can we > > > finally make progress with this and not create yet another dependency? > > > > To make it clear. I definitely do not want to block lockless printk by > > this. > > > > BTW: I am not 100% convinced that storing all three timestamps is > > worth it. It increases the code complexity, metadata size. It needs > > an interface with the userspace that has to stay backward compatible. > > Can we, perhaps, store those various "alternative" timestamps in dict so > then whoever wants to read them can just parse the dict key:value pairs > attach to each printk message? Interesting idea. It might be a way how to add optional metadata without breaking compatibility with crashdump tools. Well, I have bad feeling about it. Some of the reasons might be: + would take more space (prefix + text vs. binary representation) + not reliable because dict is currently dropped when no space + it would make the controversial dictionary feature more important I would prefer to solve this by storing the timestamps in the structure with metadata. Best Regards, Petr